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DMM EEVBlog 121GW

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This meter is partly specified by Dave from EEVBlog and made by UEI, it is packed with function, including some unique ones.

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The meter arrived in a white cardboard box with very little text on it.

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Inside was the pouch with the meter in it.

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The box included the meter, two probes, a thermocoupler, batteries, pouch and a Certificate of Conformity. There is no manual, it must be downloaded from the EEVBlog website.

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Probes are branded with B.T.C. and are rated for up to CAT IV 1000V. The meter is “only” CAT III 600V.

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The tip has 3 different configurations.

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The plug is fully shrouded and standard probe plug size.

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A standard thermocoupler with a standard dual banana connector.

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The meter is heavy and the tilting bale can hold it while the range switch is used and when the buttons is pressed carefully.

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The meter is rather thick.

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There is a micro SD card next to the fuse, it is used for firmware updating, for logging and the calibration can be stored on it.

Display

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The above picture shows all the segments on the display.

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Normal DC voltage with voltage, bargraph and temperature. The secondary display will often shows meter temperature.

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Battery voltage, it requires one or more presses on SETUP to display it.

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A configuration options (Auto Power Off), to change it: Hold SETUP down until it blinks, then use arrows to change it, hold SETUP to save value.

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Burden voltage, it is in mV, but the m is placed a bit far from the V.

The secondary display has a couple of functions:

Meter internal temperature (Ambient temperature)
Frequency in VAC and mVAC mode.
dBm in VAC mode.
Optional burden voltage in current modes
Volt and current in VA modes (Toggles between them).
Diode test voltage, either 3V or 15V
Entries when logging to card or displaying data
Configuration settings.

Functions

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Buttons (Range selection and a few other are remembered):

Range: Switch to manual range and select range, hold down to activate automatic ranging again. In diode mode it will switch to 15V diode test
Hold: Freeze the display, press again to for automatic hold when reading is table and press a 3. time for to return to normal mode.
REL: Store current reading and show further readings relative to this value. Hold down to active LPF in VAC.
1msPeak: Capture peak voltage, this only work in VAC where it will capture a positive or negative peak, result is without any sign. Hold down to turn bluetooth on.
Mode: Select the red function on the rotary switch (These selection are remembered). Hold down to turn background light on.
Min/Max: Capture min/max/avg values, there is a position to show actual value. Hold down to disable.
Mem: Press to see saved values, hold down to start logging. Time interval is changed in configuration.
Setup: Controls secondary display and configuration, hold down to change and hold down to confirm changes.

The two arrows above REL and 1msPEAK are used together with MEM and SETUP.
REL, MIN/MAX, 1msPEAK and MEM disables autorange.

Rotary switch:

Off: Meter is turned off.
LowZ: Low impedance voltage measurement, meter is fixed in 600V range and can measure both AC and DC.
V: Voltage DC, AC, AC+DC, in AC it is possible to show dBm on secondary display (Use SETUP)
mV, Temp: Millitvolt DC, AC and temperature from thermocoupler
Hz: Frequency, 1/frequency (ms) and duty cycle.
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Clik here to view.: Resistance, continuity, diode and capacity. Use the RANGE switch for 15V diode test.
mVA/VA: Volt Ampere for DC and AC, this function requires connections to both volt and current terminals on the meter.
uA/uVA: Micro ampere and micro volt ampere for both DC and AC
A/mA: Milli ampere and ampere for AC and DC.
Off: Meter is turned off.

dBm uses 600ohm reference impedance.

Input

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A 500mA: The high mA range and the A ranges, also used for VA.
mAuA: The lower current ranges, also used for VA.
CON: The common terminal for all ranges.
xxx: All other ranges including VA and burden voltage.

Measurements

Volt and frequency
- Frequency input will trigger on 1V rms as long as the average voltage is within +/- 2.3V
- At 1Vrms frequency input range is from 1Hz to 1MHz
- Duty cycle works from 10% to 93% at 100kHz with 4Vpp, precision is within 1.6
- Duty cycle works from 1% to 99% at 10kHz with 4Vpp, precision is within 0.3
- The ms reading do not show pulse width, it is 1/frequency.
- 1 VAC is 5% up at 134kHz (RMS will not work at the frequency).
- 1 VAC with LPF (1kHz) is 5% down at 520Hz.
- Pressing the SETUP key will show dBm on the secondary display in AC.
- Max/min needs about 490ms to capture a voltage.
- Peak needs about 0.9ms to capture a voltage, it only captures a peak without sign and only in AC mode.
- Input impedance is 10-11Mohm on DC and 10Mohm on AC, AC+DC will switch between the two.
- mV DC/AC has 10Mohm input impedance up to about 2V, then it drops to a two kOhm
- Frequency input is a few Mohm up to 2 volt then it drops to 2kohm
- LowZ can show both AC and DC voltage, but requires at least 12V.
- Rated overload protection is 600VDC/VAC.
Current
- For best precision REL must be used in the low ranges (55uA, 5.5mA, 550mA), due to internal offset in the meter, this disables auto range.
- 10A range will show “OFL” above 11A
- Ampere ranges are not the usual distribution, the A terminal has 3 ranges (0.5A, 5A, 10A), this means the meter has one more current range than is typical.
- The meter can display burden voltage on secondary display (Hold SETUP, press arrow, hold SETUP, press SETUP), the value is in mV.
- The meter can measure VA (Volt x ampere), the secondary display will toggle between current (mA/A) and voltage, the primary display will show VA
- The VA ranges only works up to 55V.
- Overload protection in uA and mA: 0.4A/600V or 0.44A/600V 6×32mm fuse
- Overload protection in A: 11A/1000V 10×38mm fuse
- There is an audible warning when using non current ranges with a probe in current terminals
Ohm, continuity, diode and capacity
- Ohm needs about 4.5s to measure 100ohm
- Ohm is 2.5V open and 0.57mA shorted
- The Mohm ranges are very sensitive and will jump a bit around.
- Continuity is quick (about 25ms).
- Continuity beeps when resistance is below 30ohm (30ohm setting) and 300ohm (300ohm setting)
- Continuity has selection between 30ohm, 300ohm shorted or open in SETUP menu.
- Continuity is 2.1V open and 0.57mA shorted
- Diode range 3V uses 3.2V, max. display is 3.0000V at 0.05mA, max. current is 0.84mA shorted
- Diode range 15V uses 15.5V, max. display is 15.000V at 0.23mA, max. current is 4.7mA shorted
- 10uF takes about 4 seconds to measure.
- 9000uF takes about 16 seconds to measure.
- Rated overload protection is 600VDC/VAC
Miscellaneous
- Current consumption of meter is 5mA-6mA (17mA with backlight)
- Bluetooth adds about 5mA to current consumption.
- Build-in battery voltmeter is about 0.2V too low on my meter.
- Meter works down to 1.7V where it turns off, battery symbol is show at 4.3V (4.0V on internal meter).
- The meter reading is stable down to 3.8V where it starts to show wrong values.
- Backlight start to fade at 3.5V
- The meter often needs a couple of updates before the reading is fully correct.
- Viewing angle is good
- Display updates around 5 times/sec
- Bargraph updates much faster than number (Probably 30+ times/second).
- Backlight will not turn automatic off
- Will automatic turn power off in about 30 minutes without any warning.
- Standard probes fits perfectly into sockets on meter.
- Firmware can be updated from a microSD card
- Weight is 486g without accessories, but with sleeve and batteries.
- Size is 165 × 84 × 55mm with sleeve.
Probes
- Probe resistance 29mOhm for one.
- Probe wire is soft and 100cm long.

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A look at the capacity measurement waveform.

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Frequency input resistance.

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The LowZ uses a MOV with about 1W power dissipation.

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Input impedance in DC+AC 5V range, the 11Mohm is DC, the 10Mohm is AC.

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High DC voltage can block for AC readings.
The 5Mohm range is unstable at 1Mohm and jumps a bit more than 1%, this is more than the specified 0.3%.
I had some trouble with autoranging in AC+DC and when showing burden voltage.
Runtime is without Bluetooth.

Logging on card

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The meter is supplied with a micro SD card mounted in the internal reader. To get it out the sleeve and two screws must be removed.
The logfile is in CSV format, but cannot be configured to support European CSV format.

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The top define the starting time and logging interval, the actual logging is the main display and sometimes auxiliary values. These auxiliary values are fixed and do not depend on what is shown in the secondary display.

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With VA the logging contains 3 values.

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AC+DC is marked as ACV with ACDC option. Here I selected fast logging (Interval 0), this logs 5 times each second.

Software

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The software will scan for 121GW meters and one (or more) can be selected.

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This is the standard readout in the software, it reflects the display on the meter. Some of the buttons on the meter is also accessible.
A bad connection will lock the display, the software do not reconnect automatic when in range again, instead SETTINGS and RESCAN must be used and a extra meter will show up.

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Turning the phone horizontal will increase the display size.

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And a tap on the display will change to the chart or back. It is possible to zoom in and out on the chart.
The SAVE button will make a logfile that can be saved to a lot of different Android software, I used email.

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The email log contains a time stamp and the value from the chart, no secondary values will be included.

Tear down

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I addition to the battery cover I had to remove four screws to get inside the meter.

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As usual the circuit board is shaped to fit the enclosure.

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Two more screws and I could get the circuit board out.

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Four more screws to remove the LCD display.

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The backlight panel is soldered to the circuit board, I had to unsolder it to see the microprocessor.

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The schematic can be downloaded from EEVBlog for this meter, but I will add some explanation anyway.
The current input has the usual 3 shunts, one wire and two resistors (R43, R33: 1ohm, 100ohm), but to get the low burden voltage there is a OpAmp (U8: MAX4238) with 10 times amplification next to the shunts, that is used for some current ranges. As usual the uAmA input is protected by a diode bridge (BD1) and due to the low burden voltage it do not need an extra diode. The detection of plugs in the current terminals goes to a dual OpAmp (U5: TL272C).
At the voltage input is a lot of PTC’s, there are the two input paths (PTC, PTC4) with series resistors )R16 & R17: 1kOhm) and MOVS (MOV1, MOV2, MOV3) and then there is the LowZ path with two PTC’s (PTC1 & PTC2) in series. The input resistor (R11: 10Mohm) is ceramic and there is a frequency compensation next to it (R9: 30kOhm, C13: 6pf) that can optionally be used. The meter has one transistor pair for protection (Q3 & Q5) and there is space for one more (Q1 & Q2), but there a transient diode (D13) is used instead)
Generally there are many multiplexers on the board (U9: HJ4053, U11: HC4053, U15:HC4052, U16:HEF4053). The 15V boost converter (U10: RT9271) is near the top of the circuit board,ear a SMD inductor (L1).
The multimeter chip (U3: HY3131) is close to the true RMS converter (U17: AD8436), there is also a reference in the area (ZD1: ADR3412). The bluetooth interface is a module (U6: BLE112). Near the buzzer is some hut melt glue, it secures a watch crystal for the RTC (U7: NJU6350R), this device is powered from the coin cell (CR1220) when the meter is off.

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This side has the current terminals detection input (R51, R52, R54, R55: 4×4.7Mohm) from the split terminals, it has the pads for the rotary switch, the buttons and the LCD and it has the microprocessor (U4: STM32L152ZDT6 ARM Cortex-M3, 384k flash, 48k ram, 12k EEPROM)

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Conclusion

It is an fairly advanced meter with some unusual functions like: 15V diode test, low burden voltage, VA measurement, SD card.
The meter has all the standard function for a good multimeter and also has all the common functions for a advance multimeter like: Bargraph, dual-display, average, peak, auto hold, logging, Bluetooth.
All this may sound like the perfect meter, but there are a couple of issues (There is a thread on EEVBlog), some of them will probably be fixed with software updates other is due to the design. The low burden voltage means a offset in some current ranges (Can be removed with REL). The meter is also a bit on the slow side.

For me the two most interesting functions are 15V diode test and low burden voltage, because I do not have them on other meters. The VA is fine for some DC measurement, but cannot measure AC power.

Notes

I got this meter from a Kickstarter campaign, as is often the case there was some extra delay, in this case about 4 months for second batch.
EEVBlog 121GW here is manuals, schematic and sale of the meter (when in stock).
The meter used firmware version 1.22 and during review I found a few issues, I reported some of them them to EEVBlog.

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DMM UNI-T UT139S

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Uni-T has a large selection of DMM in their program, this model exist in A, B, C, E and S versions, In this review I will look at the S version that is the most advanced model (Together with E) and has a inverted LCD display.

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The meter arrived in a red box with Chinese writing and the dealer had added a pouch for the meter.

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The box contained the meter, probes, thermosensor and a manual in Chinese (I could download a English version).

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The probes are branded UNI-T and rated for 10A and 1000V. As usual the CAT rating depends on mounted or unmounted tip cover.

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The plug is fully shrouded and the shroud is slightly shorter than standard probes.

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The thermocoupler has a single connector to the multimeter end, that is considerable better than the two loose banana plugs.

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The tilting bale is just about stable enough to change range and use switches with one hand. The tilting bale is not locked in either position.

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The 600mA fuse is accessible from the battery compartment.

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The battery lid holds the screw.

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Display

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The above picture shows all the segments on the display. Due to the way the display works some of the segments can have a fixed color.

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Typical display during usage, it will show the number and what measurement is selected.
The circle with arrow shows that auto power off is enabled, hold down SELECT when turning on to disable this.

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The electric field detection (NCV) shows from 1 to 4 bar depending on field strength and a red led will turn on together with the buzzer.

Functions

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Buttons:

Range: Switch to manual ranging and will also change range, hold down to get back to automatic
Max/Min: Starts recording min/max values, press the button to change between min/max (Both are saved), hold down to exit.
Rel: Uses the current value as reference and will show all further readings relative to this, will change to manual range.
Hz %: Select Hz and duty cycle display, works on all AC volt and current ranges.
Hold/light (Yellow): Will freeze the display, hold down to turn change brightness of the background light (Reduce it)
Select/LPF(Blue): Selects the ranges printed with blue on the rotary switch.

Rotary switch:

LoZ: Low input impedance for AC voltage, this connects a PTC across the voltage input.
Off: Meter is turned off
VAC: Show AC voltage, use Select for LPF and “Hz %” for frequency an duty cycle.
VDC: Show DC voltage.
mV: Show DC and AC voltage, use Select for AC and “Hz %” for frequency an duty cycle. This is the high speed frequency input.
ohm: Resistance, continuity, diode and capacitance.
°C: Temperature input, use Select for C/F selection.
uA: Current DC and AC, use Select for AC and “Hz %” for frequency an duty cycle.
mA: Current DC and AC, use Select for AC and “Hz %” for frequency an duty cycle.
A: Current DC and AC, use Select for AC and “Hz %” for frequency an duty cycle.
NCV: Non contact voltage, i.e. electric field.

Input

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10A: High current, it can only withstand 10+ ampere for a short time (Fuse is 10A).
mAuA: The lower current ranges, the selector switch will change between two different shunts (Fuse is 600mA).
COM: The common terminal for all ranges.
xxx: All other ranges, including external current clamp.

Measurements

Volt and frequency
- Frequency counter and duty cycle can only be selected in AC ranges.
- Frequency input requires a zero crossing.
- At 0.1Vrms frequency input range is from 0.8Hz to 6MHz
- At 1Vrms frequency input range is from 0.9Hz to 29MHz
- Max/min needs about 380ms to capture a voltage, the function will not capture the full voltage at the first peak, but needs multiple peaks.
- 1 VAC is 5% down at 2.1kHz, rms will not work at this frequency
- 7 VAC is 5% down at 650Hz with LPF
- LPF locks range to 600VAC
- Duty cycle works from 2% to above 99% at 100kHz with 1Vpp, precision is within 0.4 (Mostly 0.1).
- Input impedance is 10-11Mohm on DC and AC
- Input impedance is 11Mohm on mV DC and 5Mohm on mV AC range up to about 1V where it drops to 2kohm at 5V
- Frequency input impedance is 5Mohm at 0.1V, dropping to 2kohm at 5V
- Voltage ranges are rated for 600V DC/AC input.
Current
- Frequency counter and duty cycle can only be selected in AC ranges.
- Meter has audible alarm on 10A range when current is above 19A and shows OL above 20A.
- 10A range protected with a 10A/600V 6.3×25mm fuse
- mAuA range is protected with a 0.6A/600V 6.3×32mm fuse
Ohm, Continuity, diode and capacity
- Ohm needs about 2.5s to measure 100ohm
- Ohm is 1.0V open and 0.4mA shorted
- Continuity is very fast (About 10ms).
- Continuity beeps when resistance is below 50ohm
- Continuity is 1.0V open and 0.4mA shorted
- Diode range uses 3.3V, max. display is 3.000V at 0.15mA, max. current is 1.7mA shorted
- 70000uF takes about 7 seconds to measure.
- 10uF takes about 4 seconds to measure.
- Range are rated for 600V input.
Miscellaneous
- Current consumption of meter is 21mA with normal backlight and 11mA with low backlight
- Meter works down to 2.4V where the display goes dark and the buzzer will warn and turns off, battery symbol show at 2.6V.
- Backlight is fairly stable until display turns off.
- Reading is stable with varying battery voltage.
- The meter usual need a couple of display update to reach the final value.
- Viewing angle is good, except from top
- Display updates around 3 times/sec
- Bargraph updates at the same speed as the numbers.
- Backlight is always on and has two brightness levels, default is high.
- Will automatic turn power off in about 15 minutes.
- Standard probes fits fine, but cannot be seated fully.
- Weight is 365g without accessories, but with batteries and sleeve.
- Size is 176 × 81 × 48mm with sleeve.
Probes
- Probe resistance 38mOhm for one
- Probe wire is soft and 88cm long.

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A look at the capacity measurement waveform.

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Frequency input impedance depends on voltage.

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Meter specify 3Mohm input impedance, it is around that at 0.6V

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The LowZ uses a PTC and regulates to about 0.5W load.

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Meter is not very stable or precise at very high ohm values (50Mohm+)
Runtime is based on a Duracell Pro Power discharged at 20mA

Tear down

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3 screws (One was for the battery cover) and the back could be removed.

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The circuit board was mounted with 3 screws and 4 screws for the input terminals.

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Current input uses the fuses, as usual there is a wire shunt for 10A range and some resistors for uA (R19: 99ohm), mA is a bit larger (R20: 1ohm). Both uses some diodes (D3, D4, D5, D6, D7) for protection. A nice detail on the 10A shunt is that there are sense wires connection where the shunt is soldered to the circuit board.
The voltage input has a couple of PTC’s and MOV’s. There is two input paths each through a PTC and with a MOV after the PTC, the 3th MOV is common. Path 1: PTC1 and SG4, after the PTC it splits into a 10Mohm (R1..R4: 4×2.5Mohm) path and a 900kOhm (R42, R43, R44: 3×300kohm) path. Path 2: PTC2 and SG2, this path also has a LowZ PTC (PTC3) and is used for ohms output. The last MOV (SG3) is common for the two other MOV’s.
On path 2 there is two transistor pair (Q4 & Q5 and after optional 1kOhm (R29) Q2 & 3) the is used for protection in temperature and ohm ranges. The 1kOhm resistor (R29) cna be disabled with a analog mux (IC5: SGM4157).
Some of the diodes (D9, D10, D11, D15) are probably related to range switch encoding, the other diodes for protection (D16, D17, D18). It looks like there is a boost converter (IC3: marked SC9HE) for the background light.
The meter uses a 6000 count multimeter chip (IC1: DTA0660) with a EEPROM (IC2: 24C02), this chip has help from a processor (IC4: HY11P14: 8K ROM, 512 byte data). This processor has a ADC that have enough resolution for a multimeter, but it lacks the multimeter support circuit.

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To remove the cover around the display I had to remove two screws.

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This side only has the pads for the switches and for the LCD, there is also a few LEDs.

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Two of the LEDs are the background light, this module is soldered directly to the circuit board.

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A look under the backlight module, there is no parts here.

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At the top of the circuit board is the NCV led and antenna.

Conclusion

This meter has all the common ranges and functions for a good multimeter, but do not have the more advanced functions. The reverse display is a novelty (Get UT139E for normal display and longer battery life) and means considerable higher battery consumption
With large ceramic fuses, MOV’s, PTC’s and multiple resistors in series the protection looks fairly good.

I will call it a good basic meter, both for low volt and mains usage.

Notes

UNI-T sell rebranded versions of their meters, i.e. you can probably get this meter with another name on it.

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DANIU 1M 4mm Banana Plug to Alligator Clip

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Official specifications:

Color: Blue,Black,Red,Green, Yellow
Material: Copper
Plug size: 4mm
Suitable For: Testing
Length: 1M

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The plastic bag do not list any specifications.

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There is five different colors.

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The actual plug is 16mm long and the thick part adds 1.6mm (My other plugs are 17.5 to 20mm long). The plug gave good contact in all the devices and binding posts I tested in.

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It is possible to stack the plugs. Other brands of banana plugs fit nicely into the back.

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The other end of the cable is an alligator clip, the spring is a bit tight requiring some pressure to open it.

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The wire is soldered to the alligator clip, this makes repairs easy, but is not as solid as a crimped solution. The strain relief it not crimped either!

Test and measurements

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The alligator can hold a 24SWG (Ø 0.56mm) wire very tight and solid.

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It is also possible to grip a 7.3mm threaded rod

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The wires are 95cm long on all cables measured from end of strain relief to strain relief on alligator clip at the other end (i.e. strain relief not included).
I measured ohm by using the “Front+back” setup, this gives the resistance of the wire and internal connection to the plug, this is 20mOhm for one cable, this gives an estimated 18AWG or 0.8mm2 for the cable.
The “All” row is all five cables connected together in one long string, this means 5 times cable resistance and 4 times contact resistance (Alligator clip to banana plug).

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I did one measurement that included resistance between socket and plug. The red alligator clip supplies current and the yellow is used to measure voltage.
This setup was used for “Front 10A” column.

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To eliminate the contact resistance I can use both ends of the plug, this way I only measure the actual cable resistance.
This setup was used for “Resistance” and “Front+back 10A” column.

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M1: 39.6°C, M2: 42.1°C, HS1: 45.2°C

I uses 10A current for 15 minutes before taking the temperature photo.
It looks like the maximum temperature increase is about 15°C, this is not bad for alligator clips at 10A
With 10A current the voltage drop increased from 1119mV to 1158mV after 15 minutes

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It do have fairly many thin strands, making the cable flexible.

Conclusion

The alligator clips are a bit on the large side, but has a very good grip and low resistance.
They are good test cables also when the current is some amperes.

Notes

The cables was supplied by Banggood for review

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Gear Reviews

DMM Keysight 34461A 6½ digit

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This is a fairly expensive 6½ digit bench multimeter from a top quality brand.
This meter has many possibilities and I will not cover everything it can do.

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It arrives in a big very solid cardboard box with the DMM well protected inside and a box with all the accessories.
It includes a calibration certificate, this list the reading and the error at many different calibration points and the date this was measured.

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In the accessories box is probes, mains cable, CD with manual and a bit of documentation. The manual can be downloaded from Keysight (It is nearly 600 pages in English).

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The probes includes a few accessories.

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Standard probe, note that this probe is a fairly low safety rating, like the DMM (CAT II).

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With extended probe tip.

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With hook.

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There is two types of hooks included.

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The meter can be used in multiple position, the flat position is often used to stack it with other equipment. It can also be used floor standing. It is possible to buy a bracket for mounting one or two meters in a rack.

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The front has the display, the buttons and one set of inputs.

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On the back is another set of input and a few other connections, including the mains input.
There is also a cover for the optional GPIB interface.

Display

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This meter is a computer that needs some time to boot and do self test, during that time it shows a couple of boot screens.

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Typical display when measuring without any of the more advanced stuff activated.

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Secondary display enabled and showing AC (When showing DC & AC a relay inside the meter will toggle). The statistic can show max/min/average and a bit more.

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A bar can be added to the display.

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There is also some modes where it shows the data graphically.

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Ohm can be done both as two wire or four wire, difference here is about 30mOhm due to the cables.

Functions

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DCV/DCI: Select DC voltage or DC Ampere if Shift is pressed first.
ACV/ACI: Select AC voltage or AC Ampere if Shift is pressed first.
Ohm2W/Ohm4W: Select ohm with two wire or with four wire if Shift is pressed first.
Freq/Capacity: Select frequency or capacity if Shift is pressed first.
Cont/Diode: Select Continuity or diode if Shift is pressed first.
Temp: Select temperature measurement (This do not support thermocouplers).
Run/stop/reset: Start/stop measuring or reset meter to factory settings if Shift is pressed first.
Single/Probe Hold: Take a single measurement (Used after stop is pressed) or enable auto hold if Shift is pressed first.
Null/Math: Enable relative measurement or min/max/average (Math can do more than that) if Shift is pressed first.
Display/Utility: Modify display with bargraph, trend chart or second display. If Shift is used it is possible to change configuration.
Acquire/Help: Trigger, number of measurements, saving of measurements. There is also some help available (Holding any key down will show help for that key).
Shift: Select the function listed above the key.
Arrows: Adjust settings.
Select: Select value adjusted with arrows.
+/range/-: Shortcut to select manual/auto range and select range.

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The buttons beside the screen select the basic function, all adjustment and settings are done with these 6 soft keys. There are settings for each function (DCV/DCI/ACV/….). Display do also have many interesting settings for the different function.
The Probe Hold, Math, Utility and Acquire have more general setting, many of them related to the actual measurements.

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On the other side of the display is the power button, this is a soft power button.
The usb connector can be used to save settings and screen captures.

Input

The inputs are only CAT II 300V rated, i.e. the meter is not designed for installation and service on electric installations.

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Input HI: The voltage, frequency, capacity, diode and ohm positive input.
Input LO: The voltage, frequency, capacity, diode and ohm negative input.
Sense HI: Four terminal ohm and voltage ratio positive input.
Sense LO: Four terminal ohm and voltage ratio negative input.
3A: Low current range, it is not recommend to use it up to 3A, it has very high burden voltage.
10A: High current range.
Switch: Select between this set of input terminals and the rear terminals.

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Rear input terminals, the 10A input is replaced with a fuse for the 3A range. This is a “normal” 20mm fuse (Inside the meter is a big high current 3A fuse).
The trig input is used to start a measurement (Usual it will start automatic) and “VM Comp” signals when a measurement is done.
The LAN and USB connectors is for controlling and reading values from the meter.

Measurements

Volt and frequency
- At 10mVrms frequency input range is from 1Hz to 490kHz
- At 1Vrms frequency input range can be stretched to 920kHz
- Frequency input do not require a zero crossing.
- 1 VAC is 5% down at 320kHz, rms will not work at this frequency
- Frequency can be selected as secondary display in AC ranges.
- AC voltage can be selected as secondary display in DC ranges (A relay will toggle).
- Input impedance is 10Mohm on DC and AC
- DC ranges below 12V can be set to high impedance.
Current
- AC current can be selected as secondary display in DC ranges (A relay will toggle).
- Frequency can be selected as secondary display in AC ranges.
- The 3A range is for combability with an old model, use 10A instead.
- 3A and 10A ranges is protected by two 11A/1000V 10×38mm fuse.
- 3A and lower ranges is protected with a 3.15A/500V 5×20mm time delay ceramic fuse in addition to the large fuse.
Ohm, Continuity, diode and capacity
- Ohm needs about 1.2s to measure 100ohm in default configuration.
- Ohm is 10.7V open (100M range is 5V) and 1mA shorted
- Continuity is very fast (Less than 3ms).
- Continuity beeps when resistance is below 10ohm.
- Continuity is 10.7V open and 1.0mA shorted
- Diode range uses 10.7V, max. display is 5.0V at 1.0mA, max. current is 1.0mA shorted
Miscellaneous
- Power consumption when on 9 watt
- Power consumption when off 0.5 watt
- The meter reach final value in one to two readings.
- Viewing angle is good.
- Display update speed depends on settings.
- Maximum measuring speed is 1000 readings/second (At high speed it will have less digits).
- Weight is 3760g without accessories.
- Size is 300 × 262 × 105mm
Probes
- Probe resistance 22mOhm for one.
- Probe wire is very soft and 120cm long.

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A look at the capacity measurement waveform.

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Software

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A installed meter will show up in device manager as a “USB Test and Measurement Device”.

No software is included with the meter, but there is a manual describing how to communicate with it.
Keysight sells a software that can integrate all of their advanced instruments, it is called “BenchVue”. The licensing of this software is fairly advanced with payment for instrument types, functions, period.

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When starting the software it shows all the equipment it can find, double click on something to use it.

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But you cannot just use it, a special application for the type device must first be downloaded and installed, this is basically automatic and you get a trial period, but to continue using it a license fee must be paid.

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One multimeter is started, I can control the settings and see the actual value on the meter.

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Or I can switch to the data logger.

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The data can be exported as screen dump or CSV files.

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The CSV file uses the correct format (For my location) and includes a header with some information about the meter and settings.

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In BenchVue it is possible to run many instruments simultaneous and make scripts (With blocks) for automating tests.

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When doing your own software it is possible to use Keysight Command Expert to help building the commands. This software can also work in demo mode, i.e. without any instruments connected to the computer.
Before it can be used Keysight IOLibSuite must be installed, including a license manager. Both software packages are free.

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The software knows all commands each instrument supports (It will download a file for it) and it is possible to visually build configuration and queries for a instrument.

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The result can then be exported in a couple of formats.

Tear down

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3 screws and the cover could be removed.

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On the circuit board the front/back switch can be seen and the two large fuses for the current range.
There is some relays to switch between functions.

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The shield over the circuit board can be removed with one screw (It is a bad idea to touch the circuit board). The white round device on the circuit board is the voltage reference.

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A closer look at the backend, there is a connector for the GPIB interface.

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Behind the front panel is some electronic and a battery for the real time clock.

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There is a single big chip on the bottom of the circuit board and again it is shielded.

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This shield is removed with the same screw as the top shield.

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Conclusion

Bench DMM’s is fairly expensive, this model is at the cheap end for good bench meters from a premium brand. What you get with the bench meter is precision, connectivity, speed and some functions that is missing from handheld DMM’s (It is also missing some functions that are common on handheld meters). The range with best precision on DMM’s is the DC voltage, current and AC has less precision. On this meter capacity is an afterthought (It was not even present on the first batch).
Generally benchmeters are only CAT II 300V rated, they are not supposed to be used “out in the wild”.

I like this meter and compared to a top of the line handheld DMM it is not that expensive but can do much more.

Notes

Keysight has four bench multimeters: 34460A, 34461A, 34465A and 34470A, each higher number has a bit better precision and a few more functions. For all of them it is possible to buy more functions (But you cannot buy upgrade to next model).

I uses a couple of these meter for many of my tests together with some software I have written.

How do I review a DMM
More DMM reviews

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Gear Reviews

DANIU 1M 4mm Banana to Banana Plug Shrouded P1050

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Official specifications:

Color: Blue,Black,Red,Green, Yellow
Current: 20A
Voltage: 2000V
Plug size: 4mm
Length: 1M
Wire gauge: 1mm2

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The plastic bag do not list any specifications.

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There is five different colors.

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The plug are shrouded, this means they will only fit into connectors designed for that. They are used on multimeters, power supplies and a lot of other newer test equipment.
The shroud is 19.3mm long, this is slightly short, but means it works fine with multimeters that are designed for a slightly short shroud.

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It is possible to stack the plugs. Other brands of banana plugs fit nicely into the back.

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Non-shrouded banana plugs will. of course, also fit in the back, but the shrouded version cannot be plugged into the back of ordinary banana plugs.

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The tip is isolated, this is good when working with mains voltage.

Test and measurements

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The wires are about 95cm measured from end of strain relief to strain relief at the other end (i.e. strain relief not included).
I measured ohm by using the “Front+back” setup, this gives the resistance of the wire and internal connection to the plug, this is 20mOhm for one cable, this gives an estimated 18AWG or 0.8mm2 for the cable.
The “All” row is all five cables plugged together in one long string, this means 5 times cable resistance and 4 times contact resistance. The contact resistance from cable to cable is much better than to my sockets.

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When measuring internal resistance I use a 4 terminal setup, but this do not eliminate the resistance between the socket and the plug. The red alligator clip supplies current and the yellow is used to measure voltage.
This setup was used for “Front 10A” column.

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M1: 39.9°C, M2: 47.4°C, M3: 43.8°C, HS1: 52.0°C
I uses 10A current for 15 minutes before taking the temperature photo.
The contact resistance increases the temperature of the connectors.
It looks like the maximum temperature increase is about 20°C, it would be about double with 15A and four times with 20A, I would be careful with anything above 15A.
With 10A current the voltage drop increased from 1159mV to 1179mV after 15 minutes

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This cable can be used on mains voltage, I did a isolation test from the aluminium foil to the conductor with my usual 4242 VDC (Same as 3000 VAC) and there was no problem (I did put the foil directly across the front end of the plug).

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The isolation is fairly thick. With my caliper I measured the outer diameter to 3.8mm. It is not high temperature resistant, a solder iron at 150°C can mark it, at 350°C it will slowly melt the isolation.
For high voltage test leads I do prefer double isolation, that means two separate layers around the copper, the inner one is usual white. This means if at any time there is a scratch on the cable that looks white, it is time to replace the cable.

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It do have fairly many thin strands, making the cable flexible.

Conclusion

These test leads looks good, the resistance is low, but there can be some contact resistance.
When working with voltage above 50V it is a very good idea to use this type of test cable for better safety.

Notes

The cables was supplied by Banggood for review

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Gear Reviews

DMM UNI-T UT61E

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This is a old UNI-T multimeter and I have looked at it before, but I wanted to update the review to same standard as my current multimeter reviews. For the review I bought a new UT61E from China, this way I can also see if the protection in the Chinese version has been upgraded (The EU version has upgraded protection).

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There are 5 meters in the UT61 series and the box do not show the E model or list any specifications.

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In the box was the meter, the probes, A RS232 cable, a CD with software and a manual (Both software and manual can be downloaded).

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Probes are branded UNI-T and rated for 20A. They do not include tip covers, this means the CAT III & CAT IV rating is wrong.

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The plugs are fully shrouded, the shroud is a bit short

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On this meter this adapter can be used when testing resistors and diodes, it uses the mAuA terminal as ground, this will add about 0.4ohm error to ohm measurements.

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The meter is heavy enough to keep it stable while turning the range switch, this means it can easily be used with one hand, either lying flat or standing.

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Display

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All the segments are shown during power on, not all of them are used.

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Typical display during usage, it will show the number and selected measurement. The communication marker is always on.

Functions

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Buttons:

Hold: Will freeze the display reading, until pressed again
Range: Select manual range and change range, hold down to reactivate automatic ranging.
Rel: Shows values relative to current value, will also select manual range. Press again to disable.
Peak: Capture very fast min/max values, will also select manual range. Hold down to disable.
(Yellow): Select frequency/duty cycle in AC voltage and current modes.
(Blue): Select AC/DC in voltage and current mode, in ohm mode it will change between ohm/continuity/diode

Rotary switch:

Off: Meter is turned off
V: DC and AC voltage, use blue button to change and yellow button for frequency.
mV: DC and AC millivolt, use blue button to change and yellow button for frequency.
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Hz: Logical frequency input.
uA: Micro ampere DC or AC, use blue button to change and yellow button for frequency.
mA: Milli ampere DC or AC, use blue button to change and yellow button for frequency.
A: Ampere DC or AC, use blue button to change and yellow button for frequency.

Input

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10ADC: 10A DC current input.
uAmA: Micro and milliampere input.
COM: The common terminal for all ranges.
xxx: All other ranges.

Measurements

Volt and frequency
- 1V AC reading is 5% up at 38kHz, rms will not work at that frequency
- Frequency input do not require a zero crossing, it can handle average from an about -4.5V to more than 8.5V with 1Vrms input.
- At 1Vrms frequency input range is from 3Hz to 78MHz
- Duty cycle works from 10% to 95% at 10kHz with 1Vpp, precision is within 1.2.
- Duty cycle works from 5% to 95% at 100kHz with 4Vpp, precision is within 0.5.
- Meter has audible alarm when V range is on overload (OL), not mV.
- Peak max/min needs about 0.1ms to capture a voltage, with very short pulses it need a few.
- Input impedance is 10-11Mohm on DC and AC
- mV DC/AC is high impedance below 3V, then drops
- Maximum voltage is 1000VDC 750VAC
Current
- 10A range is fused with a 10A/240V 6.3×25mm fuse
- mAuA range is fused with a 1A/240V 6.3×25mm fuse
- Meter has audible alarm when range is on overload (OL)
Ohm, continuity, diode and capacity
- Ohm needs about 1.2s to measure 100ohm
- Ohm voltage is -0.39V open and -1.6mA shorted.
- Continuity is very fast (About 3ms).
- Continuity beeps when resistance is below 30ohm.
- Continuity is -3V open and -1.6mA shorted
- Diode range uses 2.9V, max. display is 1.8999V at 0.6mA, max. current is 1.9mA shorted
- 10uF takes about 0.6 second to measure.
- 70000uF takes about 13 seconds to measure.
- Overload protection is 1000VDC 750VAC
Miscellaneous
- Current consumption of meter is between 1.5 and 4mA, typically around 2.5mA, duty cycle in voltage and current is 4mA
- Meter turns off at 1.6V, battery symbol show at 5.5V.
- Readings will be correct until meter turn off.
- Viewing angle is good
- Display updates around 2 times/sec
- Bargraph updates faster than numbers.
- Meter will not automatic turn off, due to the always enabled computer connection.
- Standard probes fits.
- The meter usual shows the correct value at second update.
- Weight is 352g without accessories, but with battery.
- Size is 180 × 88 × 44mm
Probes
- Probe resistance 43mOhm for one.
- Probe wire are 93cm long.

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Waveform while measuring 1uF

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mVDC is high impedance up to about 3V.

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mVAC is also high impedance.

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Frequency input has variable input impedance.

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There is a hole in the frequency counter range, because the meter adds a extra digit.
The 220Mohm range is very sensitive to noise.

Software on PC

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The software and RS232 cable for a computer connection is supplied. The software is on a mini CD (Can also be downloaded), it contains the software and a very basic manual for the software. The software only supports COM1 to COM4, this is very limiting.
The software is version 4.01 from 2011, CD and download is same version.

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The adapter is slided in at the top of the meter.

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When starting the software looks this way on a Windows 10 computer. Everything is in this view, there is no other screens (Except save and load dialogs).

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Connected to the meter and receiving data, the chart do change down to a 2V scale, this is the lowest scale in voltage.

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It is possible to zoom the chart to full the entire window.

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The chart can be save in BMP format, if the zoomed chart is saved it will be larger.

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The software do not support peak capture mode, the meter will alternating transmit max and min captured value and the chart shows it this way. The logfile is the same way with no indication that peak mode is active.

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The logfile is a TAB delimited file with a .xls or .txt extension. Excel will complain about this, but can load it correctly.

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It is also possible to save the logfile in XML format, Excel can also handle this (I have removed metadata and added line break in the above image).

Tear down

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To open the meter the battery lid must be removed and two more screws.

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As usual the circuit board is shaped after the enclosure.

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There is some shielding sticking up at the side.

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One more screw and I could take the circuit board out (Be careful to turn the screw, not some of the trimpots)

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The current inputs uses 240V fuses, but it is not made the usual way. The uAmA input has 4 resistors in series (R29 (A&B), R30, R31, R32: 1ohm, 9ohm, 90ohm, 900ohm), the two first are used for mA and four are used for uA. To avoid to high voltage drop the high value resistors are bypassed by antiparallel diodes R32, D7, D8 for uA and R30, D5, D6 for mA. This circuit gives a fairly high burden voltage in some current ranges. There is also diodes directly across the uAmA input (D1, D1A, D1B, D3, D3A) this is a bridge with one diode between + and -.
The voltage input has 3 paths, each with their own PTC, but the MOV is missing. PTC3 is the voltage input and goes to a 10Mohm resistor and parallel capacitor (C41A & C41B & part of R8). Output for ohm and capacity is through PTC1 with a transistor pair (Q1 & Q8) as protection. Input for ohm and capacity is through PTC2 a transistor pair (Q5 & Q6), a resistors and a trimpot (R33: 100kOhm, VR3).
To drive the buzzer is a oscillator (U3: HEF4069).
There are many trimpots and trimcaps. The trimcaps are used to adjust the high frequency AC response.

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The display is mounted with two screws and a clip.

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Part of the uAmA bridge rectifier is mounted on this side and also one of the transistor protection pairs.
The big chips (U1: ES51922A) is the multimeter chip and it has an RMS converter (U2: AD737J).

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Conclusion

UNI-T may have correct CAT rating on some of their new meters, but this one is definitely not correct and it do have the the full protection mounted (There is space for larger fuses and MOVs).
The meter has many good features and is fast in ohm, continuity and capacitance. The weak point is current, it has a rather high burden voltage, it is also missing a min/max function.

It is a good hobby meter, except for current measurements.

Notes

UNI-T do often make rebranded meters, i.e. it may exist with other names on it.
UNI-T makes a safer EU version of this meter, it is also possible to buy a USB interface cable.

It is possible to find a schematic of the meter on the internet, but it do not match completely.
The old review The circuit board has been upgrade since then, but the software is still the same version.

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Just received this little beauty and for my first post I thought I would share:
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Gear Reviews

DMM Aneng AN302

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The brand Aneng has a lot of cheap multimeters, most of them fairly good. This meter is a pocket meter, except that is missing a compact pouch for pocket use.

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I got the meter in the usual black plastic bag with some protective wrapping around the pouch.

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The pouch with the meter in it, it will fit in a large pocket.

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I got the following pieces: the DMM, a pouch, a lanyard and a instruction sheet.

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The probes a small and without tip cover, that means CAT II. They are marked 250V and the meter is marked 600V, this do not really match up with non-replaceable probes.

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The meter do not have a range switch, only buttons, this means it will never slide around when selecting range.

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But the buttons can get stuck, I also had the FUNC switch non-working a couple of times, but could get it working again without opening the meter.

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Replacement of battery requires removal of small 3 self tappers, it will probably limit the number of times it is possible to replace the battery.

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The meter do not have background light, instead it is a flashlight.

Display

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The above picture shows all the segments on the display, most are used by this meter.

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Typical display during usage, it will show the number and what measurement is selected.

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The NCV is the usual bars, the buzzer and the flashlight.

Functions

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Buttons:

Hold: Freezes the display, hold down to turn flashlight on/off.
Range: Will disable auto range and change range, hold down to activate auto range.
Rel: Shows values relative to current value, will also select manual range. Press again to disable.
Select (Yellow): Select ranges, see below.
Func (Blue): Select between the two modes, there is no indication on what mode is selected, this must be inferred based on selected range.

Mode 1: VDC, VAC, Frequency, NCV
Mode 2: mVDC, mVAC, ohm, continuity, diode, capacity, frequency
The text on the meter is missing frequency in mode 1.

Input

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This meter only have a red and black probe coming out, no other connections.

Measurements

Volt and frequency
- At 100mVrms input frequency range is from 1Hz to 5.6MHz in mV mode.
- At 1Vrms input frequency range can be stretched to 6.2MHz in mV mode.
- At 1Vrms input frequency range is from 1Hz to 30kHz (Above that the display gets unstable) in V mode.
- At 5Vrms input frequency range can be stretched to 80kHz in V mode.
- 1 VAC is 5% down at 2.1kHz (RMS will not work at the frequency).
- Frequency input requires a zero crossing in both mV and V mode.
- Input impedance is 10..11Mohm on DC and AC
- mVDC range is high impedance for DC up to around 1.5 volt where it drops to 2kOhm. AC is similar, but capped at 10Mohm
- mV frequency input is 10Mohm up to around 1.5 volt, then the protection clamps to 2kOhm
- V frequency input is 10..11Mohm.
Current
- Meter cannot measure current
Ohm, Continuity, diode and capacity
- Ohm needs about 2.8s to measure 100ohm
- Ohm is 1V open and 0.4mA shorted
- Continuity is quick (About 30ms, but mostly 5ms).
- Continuity beeps when resistance is below 50ohm.
- Continuity is 1V open and 0.4mA shorted
- Diode range uses 3.2V, max. display is 3.000V at 0.13mA, max. current is 1.8mA shorted
- 10uF takes about 4.5 seconds to measure.
- 70000uF takes about 12 seconds to measure.
- Overload protection is not rated
Miscellaneous
- Current consumption of meter is 1.5 to 1.9mA depending on range with flashlight it is up to 15mA.
- Meter works down to 2.2V where it turns off, battery symbol shows at 2.4V.
- Reading do not change with battery voltage.
- Flashlight only works down to about 2.6V where it is fairly dim.
- The meter usual need a couple of display update to reach the final value.
- Viewing angle is good.
- Display updates around 3 times/sec
- Flashlight will not turn off automatic, but will turn off when meter automatic turns off.
- Will automatic turn power off in about 15 minutes.
- Weight is 74g without accessories, but battery.
- Size is 119 × 63 × 13mm width includes bent strain relief for probes.
Probes
- Probe wire is soft, fairly thin and 70cm long.

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A look at the capacity measurement waveform for 1uF.

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Input resistance in mV frequency mode depends on input voltage.

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Input resistance in mV DC mode, in AC there is a 10Mohm in parallel.

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AC input cannot handle large DC offset.
NCV is way to sensitive, just about any wire will trigger it, it do not need to carry voltage.

Tear down

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3 screws and the back could be removed.

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The inside looks very simple, but I am not impressed with the battery holder

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The lid has one connection for the battery holder, the buzzer that is heat staked to it and a lens for the flashlight.

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The circuit board is mounted with four clips, but the did not hold it fairly well and it was very easy to take out.

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The top has one connection for the battery holder, the rubber for the buttons and the LCD display. The rubber looks a bit messy, I wonder if the separate blue button is due to a repair or if it is made this way (In a teardown I saw all the buttons was one piece, i.e. it must be a repair).

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The input is always connected to the high ohmic input resistors (R22 & R28: 2×5Mohm), when ohm/mV/etc. mode is selected with SW1 the iput is also routed to the PTC (PTC1: 1.5kOhm) and a low ohmic input (R21: 900kOhm). The PTC has a transistor pair (Q4 & Q5) to handle over voltage.
The NCV has 3 resistors (R18, R29, R30: 3×20Mohm) to tie it to ground.
The main multimeter chip is behind the black blob and next to it is a EEPROM (U1: P24C02A) with calibration and mode setup.

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The two switches are soldered on this side, this will make them a bit sensitive to high pressure. The flashlight led is here and two springs for connection to the buzzer.
The switch will connect the centre pin to either top or bottom pin, separate for the two sides.

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Conclusion

As usual I do not believe the CAT rating, probes is marked 250V, meter is marked 600V and the input voltage goes to a small SMD resistor.
The meter has nearly all the function of larger meters, it is only missing current, this makes it a very universal pocket meter.
The mechanical quality for this meter is on the low side, very short self tapping screws when replacing battery and clips that are not very good at holding the circuit board. I do also miss a better “pouch” for pocket use.

Notes

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Power supply frontend DPS5020-USB 50V/20A with Bluetooth and USB interface

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This device is the front end for a power supply, it must be supplied with low voltage DC power (Up to 60V).
Official specifications:

Input voltage range: 6.00-60.00V
Output voltage range: 0V-50.00V
Output current: 0-20.00A
Output power range: 0-1000W
Product Weight: about 222g
Display module size: 79*43*38(mm) (L*W*H)
Cutout size: 71mm*39mm
Power module size: 93*71*41(mm) (L*W*H)
Length of connecting line: 200mm
Fixed hole center distance: 86mm, 64mm
Output voltage resolution: 0.01V
Output current resolution: 0.01A
Output Voltage accuracy: ± (0.5% + 1 digit)
Output Current accuracy: ± (0.5% + 2 digits)

I got it from aliexpress store: RD official store

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It arrived in a styrofoam box together with some other stuff, inside the box was the plastic box with the electronic.

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There is a control unit, a power unit, two flat cables, some rather small fork terminals, the usb interface, the Bluetooth interface, cable for usb/bluetooth and a manual in English and Chinese.

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The control unit has a display, four buttons and a encoded that can be pressed.
The V and A buttons will enable adjustment of voltage and current with the encoder, press the encoder to select digit, when finished press SET.
Holding down V/A/SET will recall a preset, with V and A it is preset 1 and 2, with SET any of the 9 presets can be selected.

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Display while off and on, set point is shown at the top of the screen and input voltage at the bottom.

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On the settings screen it is possible to define a couple of parameters: Voltage, current, over voltage, over current, over power, display brightness. The “over” settings will turn output off if they are reached.
The device has 9 preset memories. To save a preset adjust the parameters, move the marker to M0, adjust the encoded to desired preset number and hold down the SET button.

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There is a hidden communication menu, hold down the “V” button while powering on the supply to activate it (Default is fine for most applications).

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The front panel is made to be pushed into a rectangular cut-out

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The two flat cables from the power unit is connected at the back.

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The Bluetooth and USB modules are small circuit boards and a wire to connect one of them (It is only possible to connect either Bluetooth or USB module to the power module).

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Wires connected, ready to test.

Measurements

I did a huge amount of test on this unit and will only show a few of the charts here, I have posted more in another article.

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Running at low input and output voltage, the output looks stable and the fan starts at 10A.

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Increasing both input and output voltage, this time the fan starts earlier, probably due to a temperature sensor. The power lost in the unit is higher, but efficiency is better.

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Here I run at maximum input and output voltage, this means up to 20W lost in the supply, but that is not much when the output power is 1000W

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With very low output current and voltage it can maintain output voltage down to about 6V, at 20A it needs about 1 volt mere (Some of it due to losses in the input wires and connections).

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The specifications says it needs about 10% more input voltage than output voltage, it looks fine here.

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At full power output the input must be slightly mere than 10% above output voltage.

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Current consumption depends on select output voltage and input voltage, but it is fairly low, even though it has to drive the display.

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The power supply will go into constant current mode when overloaded, here I shorted the output and measured the current.

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It can even be used as a 20A constant current generator.

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The output turns on without any spikes.

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When loaded there will be some noise.

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Changing the load from 0A to 19A do not show any voltage drops.

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Changing the current from 19A to 0A do not show any voltage spikes.

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Both at low and high current there is some noise from the switcher on the output.

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The switcher is running at about 65kHz.

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It was no problem running at full output power for one hour (Except it heated my room).
After about 45 minutes I took the temperature photos below.

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M1: 68.2°C, M2: 67.3°C, M3: 69.3°C, M4: 71.5°C, HS1: 99.1°C
The input fuse (HS1) gets rather hot at this current, the output fuse (M2) not as much. The internal power supply (M3) also warms up.
None of it looks problematic.

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M1: 60.4°C, HS1: 91.2°C

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The display is precise and there is very little change with load.

Specifications says unit can be used as a charger, but there is a few problems with it:

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Power supply has input power, but output is off. A battery will be discharged with up to 200mA

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Power supply is supplying 5V output, if the battery voltage is higher than the selected voltage it will drain the battery.
The charge current is not shown in this chart, it is below the 0 line.

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Power supply do not have input power, it will drain with more than 200mA from about 3.5V

Android application

Application will show an ad for another RD product when started.
Application is not on Google.
RD uses a file download service that opens ads in minimized windows.
Protocol is documented.

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The application is basically one screen. To connect use the Bluetooth symbol, in my case I could not see the power supply and had to use the normal Android discover dialog (I did use “Scan for devices), after that it worked perfectly.

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Here I am connected. I changed a setting and saw the voltage dropout on the chart. After that I connected my oscilloscope, but did not see any dropout on the chart or the scope.

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The wheel is used to adjust voltage and current with, but only two digits at a time. Touch the U_SET/I_SET and digits to select what two digits to adjust.

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The control panel is locked while using the phone and it is not possible to unlock it. I would have preferred that at least on/off worked.

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There is not many languages in the current version of the application.

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Using the file folder will save a Excel file on the phone with a fixed name, i.e. it is only possible to save one log.

PC application

Application is a 240MB download
Inside the archive is manuals, a font, a driver and another archive with the program
Application is very slow to install.
The screen is a fixed size (1062 × 619 pixels), there is no resize options.
RD uses a file download service that opens ads in minimized windows.
Protocol is documented.

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The package uses a National Instruments library, this is large and slow to install. This installation will not install the supplied font, it has to be installed manually. The letters are a bit to large without that font.

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Program started, but not connected yet.

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The advanced tab where the presets can be configured and 3 types of automatic sequences can be defined and used.

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When connected the actual values and curves are added. The dials can be changed with a mouse or new values can be typed in the numeric fields.
On this screen the text do not fit into the boxes, this is partly my own fault, because I did not install the supplied font. Why do the installer not handle that?

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I did some voltage scans, here it is seen from the program.

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And here with a oscilloscope (Parameters are not the same).

A closer look at the electronic

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This side of the circuit board is only soldering, screws and some standoffs.

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All electronic is on this side. At the input is a 20A smd fuse and two high power mosfet (Q0 & Q4). The switcher is a TL594 and next to the heatsink is a high speed and precision OpAmp. The microcontroller is a 32F100. The board do also have a internal switching power supply (U03: XL7005A) and some linear regulators. The output has two 20A fuses in parallel.

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Front panel

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The front panel uses four clips to keep the circuit board in the box.

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The circuit board has mechanical switches, a encoded and the display.

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There is nothing hidden under the display.

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USB module

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The usb module uses a CH340 chip and two optocouplers.

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Bluetooth module

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The Bluetooth module is a Bluetooth module and a led.

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Conclusion

This module can deliver a lot of current and power when supplied with enough DC input power. The PC option may not be very nice looking, but it has some interesting functions on the advanced tab and I like the protocol is documented. The phone app has a very nice graphing and logging function, but adjustment of voltage and current is not that good.
This module is very useful to build a cheap high power bench power supply with. Add a cheap switching power supply, a box (RD sells one), some binding posts and some work.

Compared to professional units it is missing a lot: Lower noise, both numeric keypad and encoded, 4 terminal connections, larger display. But for the price it is very good and works fine.

Notes

The power supply was supplied by RD for review.

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DMM Bside ADM92

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This meter has the shape of a clamp meter, but it a normal multimeter, that can also work as a pen meter

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The meter is in a brown cardboard box with a label that shows the model and a few specifications.

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It included the DMM, a pouch, a pair of probes, a thermocouples and a instruction manual.

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Everything could fit in the supplied pouch.

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The thermocoupler is standard cheap K type with lose banana plugs.

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Probes are branded with BSide and has removable tip covers. There is a CAT III 1000V rating on the cover, but none on probe.

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The plug is fully shrouded and very close standard probe shroud size.

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The slot at the side of the meter can hold one probe and the the meter works as a pen type meter.

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When I got the meter something was rattling inside it, it was the NCV antenna. I soldered it back in place before doing any testing.
It was probably not soldered good enough and fall off due to a bump during shipping.

Display

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The above picture shows all the segments on the display, not all are used.

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Typical display during usage, it will show the main number and what measurement is selected.

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NCV has the usual bars on the display, together with a red led and the buzzer.

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The LIVE function requires one probe, shows 4 bars when not connected and LIVE when touching a live wire. Buzzer and led is also used for this function.

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The led for LIVE and NCV function is here.

Functions

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Buttons:

Hold: Freezes the display, hold down for backlight.
Hz: Will change to frequency in AC ranges.
SEL: Select between DC and AC and ohm, continuity, diode and capacitance. For temperature is will select between C and F.
V Alert: Activates the NCV mode, works on any rotary switch position except off. Pressing again or turning the rotary switch will exit NCV mode.

Rotary switch:

Live: Detect a live wire with one probe.
Off: Meter is turned off
V: Show DC or AC voltage.
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mA: The two mA current ranges.
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Input

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With only two input terminals all measuring functions are done with these.
For LIVE only the red is used.

Measurements

Volt and frequency
- Frequency counter is only available on AC ranges
- Frequency input requires a zero crossing
- At 0.1Vrms input frequency range is from 10Hz to 5.6kHz
- At 1Vrms input frequency range is from 1Hz to 45kHz
- 1 VAC is 5% down at 2.3kHz (RMS will not work at the frequency).
- Input impedance is 10-11Mohm on DC and AC
- Rated overload protection is 1000VDC and 750VAC
- Frequency input resistance is same as voltage, except at very low voltages where it is high
Current
- mA do not have a fuse but uses some PTC’s
- Will show OL above 200mA
Ohm, continuity, diode and capacitance
- Ohm needs about 2.8s to measure 100ohm
- Ohm is -1.1V open and -0.3mA shorted
- Continuity is quick (About 15ms).
- Continuity beeps when resistance is below 50ohm
- Continuity is -2.1V open and -0.3mA shorted
- Diode range uses 4.0V, max. display is 3.300V at 0.36mA, max. current is 2.1mA shorted
- 10uF takes about 2 seconds to measure.
- 9900uF takes about 9 seconds to measure.
- Rated overload protection is 600V DC or AC
Miscellaneous
- Current consumption of meter is 1.5mA to 1.7mA, with backlight it is 5.2mA
- Meter works down to 2.2V where it turns off, battery symbol show at 2.3V.
- Meter readings are stable until it turns off.
- Backlight fades with voltage and is very dim at 2.5V
- The meter usual show correct reading on first or second display update.
- Viewing angle is good, except from top
- Display updates around 3 times/sec
- Backlight turn off after about 30 seconds.
- Will automatic turn power off in about 16 minutes.
- Banana plugs and standard probes fits nicely.
- Weight is 118g without accessories, but with batteries.
- Size is 140 × 49 × 33mm.
Probes
- Probe resistance 185mOhm for one.
- Probe wire is 78cm long.

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A look at the capacitance measurement waveform when measuring 1uF.

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Frequency input resistance.

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The 9.999uF range jumps up/down at the high end, but is within the 4% tolerance.
My 11000uF capacitor measures as 1134uF, i.e. 10 times below actual value.
High DC voltage will block for AC readings.

Tear down

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To open the meter two screws must be removed, but one of the screws are behind the belt clip, this add two more screws for a total of four screws.

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As usual the circuit board is shaped to fill the enclosure.

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To get the circuit board out I had to remove four more screws.

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It looks like this enclosure is also used for meters with considerable more leds, when looking at the number of light pipes above the rotary switchs.

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Current input uses the two PTC’s (F1 & F2) and a one ohm resistor with a TVS diode across. Voltage input uses two resistors (R4A & R4B: 2×5Mohm). Ohm output uses the green PTC (R10) and a transistor pair (Q1 & Q2) for protection. The ohm sense input is 3 resistors (R15A, R15B, R15C: 300k, 300k, 390k). Temperature uses same configuration as ohms.

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On this side is the pads for the buttons, the rotary switch and lcd in addition to the NCV led.

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Conclusion

The meter has the normal functions, except current is a bit limited with only mA ranges. The shape is probably great when using the meter handheld, but on a table it is not as good.

Notes

The meter was supplied by BSide for review.

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DMM Mustool MT8206

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This is a DMM that can also show waveforms.

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I got the meter in a cardboard box with specifications on it.

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It included the DMM, a pair of probes, a bag and a manual.

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The probes are without tip covers, i.e. they are only CAT II rated.

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The plug is fully shrouded, but is slightly smaller than standard probe plug size.

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Both meter and tilting bale is smooth, this makes it difficult to use the meter one handed.

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The bag can fit both meter and probes, but feels a bit tight when doing it (Meter fits easily in it).

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Battery lid uses do not use a screw, is clipped on and has instruction on how to insert batteries (Centre battery last).

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Display

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The power on screen shows four lines. The screen always uses background light, this gives it a good contrast.

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The display will usual show the value and unit, together with a bargraph.
The display is a graphic display, this gives some flexibility with showing symbols and units.

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The display have a log of saved values.

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And it can show waveforms.

Functions

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Buttons:

DIS/Auto: Manual range, hold down to reactivate auto range. When held down in auto range the waveform display will be shown.
REL: Remember current value and show values relative to this, this function is indicated with a triangle on the display.
SELE: Change between ohm, diode, continuity and capacity in ohm mode and DC, AC in current modes.
HOLD/DS: Freeze the display value and store a value/chart, press again to release. Hold down this key to enter the log.
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Clik here to view.: Use for page up/down when showing recorded data and for adjusting time in waveform display.

Rotary switch:

Off: Meter is off.
mV: DC mV range
VDC: DC volt range
VAC: AC volt and mV range, mV must be selected manually.
Hz%: Frequency and duty cycle.
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Clik here to view.: ohm, diode, continuity and small capacity (Max. 100uF)
mF: Large capacity, up to 10000uF
mA: milliampere, use SELE to select between DC and AC
A: Ampere, use SELE to select between DC and AC
Off: Meter is off.

Input

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If you have multiple meters, be aware that this meter has placed the minus connection different than other meters.

10A: High current.
mACx: The lower current ranges, large capacitor +
xxx: All other ranges.
CON: The common terminal for most ranges, large capacitor is excluded from this.

Log function

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The lines marked 00, 01, 02, etc. are the log entries, there is space for 100 entries. The value below is the current input value.

Hold down HOLD to change into this mode.
To exit hold down HOLD, using the rotary switch will also exit this mode.
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to go a page up/down.
To clear all entries hold down DIS, when trashcan shows hold down HOLD

Waveform function

I will not call this function a oscilloscope function, but a waveform display function, it do not support enough functionality for a oscilloscope.

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Hold down DIS to change into this mode.
To exit hold down DIS, using the rotary switch will also exit this mode.
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will change the timing, i.e. show more or less of the curve.
The HOLD button can be used to store 10 waveforms, it works similar to the log function above.

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The display can be activated in mVDC, VDC, VAC, mA and A, but in DC modes there is a low pass filter. The curve above is the same curve as the first one, but this time I used VDC instead of VAC.

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10Hz 5Vpp with 2.5V offset, this means the curve must just touch the centre line, but due to the low pass filter the AC is reduced in amplitude.

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A 1kHz square wave, sometimes it is shown fine and sometimes it looks like this.

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A 10kHz square wave is completely hopeless.

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The same is a 10kHz sinus wave.

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A 1kHz sinus at lower amplitude is also a problem, the waveform display do only have the voltmeter ranges, nothing in between, that is not good enough.

Measurements

Volt and frequency
- At 1Vrms frequency input range is from 0.6Hz to 560kHz
- At 2Vrms frequency input range can be stretched to 1.2MHz, to reach the specified 5MHz the input voltage must be 7Vrms
- Frequency counter works with at least +/-8.5V offset with 1Vrms input
- Duty cycle works from 10% to 95% at 10kHz with 4Vpp, precision is within 2.5
- Duty cycle works from 1% to 99% at 1kHz with 4Vpp, precision is within 1.8
- 1 VAC is 5% down at 63kHz
- Input impedance is 10-11Mohm on DC, AC and mVAC
- Input impedance on mVDC is high
- mVAC must be manually selected
- Frequency input varies in impedance at low voltage, but at 20V it is down to 2kOhm
- There is audible alarm on overload on any voltage range.
- There is a short beep and high voltage indicator turns on when voltage goes above 24VAC or 24VDC
- Maximum voltage is 1000VDC and 750VAC, for frequency input it is 380V
Current
- mA protected by 0.5A/250V probably a PTC
- A is protected a 10A/250V SMD fuse
- There is audible alarm on overload on current ranges, except 10A range!
Ohm, Continuity, diode and capacitance
- Ohm needs about 4s to measure 100ohm
- Ohm is 0.43V open and 0.23mA shorted
- Continuity is 0.43V open and 0.23mA shorted
- Continuity is moderate in speed (About 120ms).
- Continuity beeps when resistance is below 100ohm .
- Diode range uses 1.5V, max. display is 0.999V at 0.25mA, max. current is 0.73mA shorted
- 10uF takes about 3.4 seconds to measure.
- Lower capacity selection goes to 100uF
- mF is protected by a PTC and a TVS diode.
- 100uF takes about 18 seconds to measure in low capacity selection.
- 100uF takes about 4 seconds to measure in high capacity selection.
- 11000uF takes about 18 seconds to measure in high capacity selection (Display shows about 9.200mF).
- Measuring large capacity values flashes empty battery symbol sometimes.
- There is audible alarm on overload on capacitance range
- Ohm and capacity input is rated for 250VDC/AC overload.
Miscellaneous
- Current consumption of meter is 33mA
- Display is too dark to read at 2.6V, battery symbol show at 2.9V.
- Meter reading is stable while display is readable.
- Backlight starts to fade at 3.8V
- The meter will usual show the correct value after two display updates and a update for each range step.
- Viewing angle is good, except from the top
- Display updates slightly below 2 times/sec
- Bargraph updates at same speed as display.
- Will automatic turn power off in about 15 minutes.
- Standard probes cannot be fully seated (Maybe 4mm stick up)
- Weight is 256g without accessories, but with batteries.
- Size is 160 × 82.5 × 37mm.
Probes
- Probe resistance 92mOhm for one.
- Probe wire is soft and 82cm long.

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A look at the capacitance measurement waveform for a 1uF capacitor.

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The mF range uses a much higher test current and 100uF is a very low value here.

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A 10mF capacitor is maximum that can be measured, but due to errors I could use a larger one for testing.

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Frequency input impedance.

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The mV range has high input impedance, except when voltage goes too high.

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The maximum value in each range varies slightly.
The meter can show wrong DC value when combined with AC

Tear down

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I had to remove four screws before I could open the multimeter.

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The battery cassette is mounted directly on the circuit board.

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The circuit board is mounted with five clips, no screws are used, but there is space for five screws.

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The 10A current uses a SMD fuse and the usual wire shunt, the mA range is a 1ohm resistor with a TVS diode across. The other TVS diode is used for the mF range.
The voltage input has a MOV directly to minus input and uses four resistors (4×2.5Mohm) and two capacitors in series (2×10pF 3kV). The mV range uses a PTC and a transistor pair (Next to 2 × 8pin chips) as protection. For the ohms and low capacity range the same PTC is used, but another transistor pair.
The two 8 pin chips are dual OpAmps(TLC2272) and the smaller 10 pin IC is dual analog switches (SGM3005). The large IC (CS7721CN) is a multimeter chip and microprocessor in one. The number is scraped of the second largest chip, but it has communication with the display and is connected to a EEPROM (24C64).

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On this side of the circuit board is the 10A shunt, a nice big one, the buzzer is here. Then there is pads for the buttons and the rotary switch. The display is mounted here with the backlight soldered to the circuit board and the data in a flat flex cable that is connected on the other side.

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Conclusion

As usual the CAT rating is wrong, a 250V fuse is not acceptable on a 1000V meter, but will work fine for hobby work. A MOV directly across the input is not the best idea around, it will handle small stuff, but exploded if any serious stuff hits it.
As a meter it is decent, it has a fair selection of ranges and the backlight display is easy to read with good indication of selected function.
The mains extra on this meter is the waveform display and that is a disappointment, it only works with low frequencies and the DC input is filtered way too much.

Notes

The multimeter was supplied by banggood.com for review (I believe that Mustool is a Banggood brand).

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DMM Keithley DMM6500 6½ digit

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This is a fairly expensive 6½ digit bench multimeter from a top quality brand.
This meter has many possibilities and I will not cover everything it can do.

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It arrives in a big very solid cardboard box with the DMM well protected inside.

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It includes a calibration certificate stating that the meter is in calibration, mains cable, a pair of probes and a usb cable. It do not include any manuals, they must be downloaded (Reference manual is 1200 pages).

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The meter included 3 mains cable, none of them are a perfect match for the normal Danish socket, but the Schuko works.

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Standard probe, note that this probe is a fairly low safety rating, like the DMM (CAT II).

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The plug is fully shrouded.

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The front has the display, the buttons and one set of inputs.

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The meter can be tilted, but in one angle only.

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The vent holes for the fan are on the sides.

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The back, there was a warning to check the mains voltage.

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Both back and front connectors has a cheap and easy replaceable fuse for the 3A input, inside is a large HRC fuse.

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The front and back bumpers can easily be pulled off.

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Behind the front bumper is screw holes for rack mounted brackets (All high end bench meters can be mounted in a rack).

Display

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This meter is a computer that needs some time to boot and do self test, during that time it shows the brand name. At first only the name and later in the sequence it adds a background image and a bar. Total time is about 15 seconds.

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Typical display when measuring without any of the more advanced stuff activated. Here I am measuring one of my precision resistors in 4 terminal mode (The meter is probably more precise than the resistor).

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Secondary display enabled and showing AC.

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Just about any measurement can be used for secondary display, but many of them means a relay will be toggling inside the meter.
Not all combinations of main and secondary are meaningful, but they can be selected and the meter will do it.

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The statistic can show max/min/average and a bit more.

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It is possible to include a chart on the display.

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It can be expanded to cover the full screen.
When in this state it is possible to enable cursors to measure value and time.

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When using the digitize function the meter samples very fast, this is a 100kHz sine wave. This fast sampling can be done in either voltage or current mode, this means that capturing a 10us current pulse is possible.
To change scale use two fingers on the screen to contract or expand the view.

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And a 10kHz square wave.

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The usual table view is also present, it is possible to click on a entry to get some parameters.

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The usual histogram is also present, it support panning and zooming. The maximum number of bins are 700.

Functions

The buttons do not say much about the function in the meter, because most of the user interface is done with the touch screen.

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HOME: One press will return to the measured value display, two pressed will return to the measured values with the function selection below.
MENU: The menu screen with icons for all the different configurations and functions.
APPS: Applications, this is not the same as scripts, but made in the same language.
HELP: Shows a help screen for the selected item/function.
ENTER: Activate the button with a yellow square around (Generally not very useful on this meter).
EXIT: Leave a menu/function.
FUNCTION: Select range, this is basically the same as the selection below the readout.
TRIGGER: Used to manually trigger a measurement or measurement sequence.

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The power button is a soft switch, this means part of the meter is always on and using power.
A short press will turn the meter on a longer press will turn it off.
The led next to the button is orange while off and green while on.

Input

The inputs are only CAT II 300V rated, i.e. the meter is not designed for industrial and service on electric installations.

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Front side inputs.

Input HI: The voltage, frequency, capacitance, diode and ohm positive input.
Input LO: The voltage, frequency, capacitance, diode and ohm negative input.
Sense HI: Four terminal ohm and voltage ratio positive input.
Sense LO: Four terminal ohm and voltage ratio negative input.
3A: Low current range, it is not recommend to use it up to 3A, it has fairly high burden voltage. There is a fuse inside the terminal.
Switch: Select between this set of input terminals and the rear terminals.

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Rear side inputs.

Input HI: The voltage, frequency, capacitance, diode and ohm positive input.
Input LO: The voltage, frequency, capacitance, diode and ohm negative input.
Sense HI: Four terminal ohm and voltage ratio positive input.
Sense LO: Four terminal ohm and voltage ratio negative input.
3A: Low current range, it is not recommend to use it up to 3A, it has fairly high burden voltage. There is a fuse inside the terminal.
10A: High current range, this has a large fuse behind the lid above.
Switch: Select between this set of input terminals and the rear terminals.

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The trigger in input, this is on of the conditions that can be used to start a measurement, the trigger out can be linked to other equipment that must start at the same time.
The LAN and USB connectors is for controlling and reading values from the meter.

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The piece of gray plastic can be replaced with a interface module, options are: GPIB, RS232, TSP-Link and a general I/O connector.

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The accessory is a slot for a multiplexer (Scanner) that can change between multiple tests points.

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There is also a usb connector on the front, it can be used with memory sticks for saving data, screen dumps and running or loading scripts and apps.

Some more advanced stuff

The meter has a lot of advanced functions, here is a look at a few of them.

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The displayed value can be calculated as an average of some samples (Filter), as a formula (Math), it is possible to show relative values (Rel) from either an acquired or typed value. Usual the meter will zero the input stage between each measurement (Auto Zero), but for faster readings this can be disabled. The actual sample speed (Rate) can be adjusted in power line cycles (Minimum is 0.0005 with 50Hz) and the input impedance (Input Z) can be 10Mohm or high at low voltages.

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The meter supports many different thermo sensors, but it do not have a build in temperature reference, i.e. with thermocouplers a ambient temperature must be entered manually. There exist a thermocoupler scanner card that includes a reference measurement.

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Here are all the thermocouplers it supports.

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The different types of math function that can be define. For mx+b the m and b must be typed in and for percent a reference value must be typed in.

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The main menu, behind each icon is some configuration or other stuff.

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Larger bench meters usual have a trigger function making it possible to record specific events or synchronize multiple types of equipment (Default is to measure all the time). On this meter it is very advanced.

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The meter has a script language, it can both be used for short scripts and for applications.
It is possible to automatic generate a script that will configure the instrument to the current configuration, this script can be run at any time or automatic run when meter is powered on.

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Here I run the “Clock” application and it takes over the normal screen.

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Data is saved to the usb memory stick is in CSV format and do not include any secondary display.

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The time format can be in multiple formats, here I use something called “Relative”

Measurements

Volt and frequency
- At 10mVrms frequency input range is from 1.5Hz to 720kHz
- At 1Vrms frequency input range can be stretched to 1MHz
- Frequency counter works with at least +/-8.5V offset with 10mVrms input
- 1 VAC is 5% down at 390kHz, rms will not work at this frequency
- Period is 1/frequency, it do not show high/low period time.
- Meter can show dB(m) with any reference voltage or a any reference impedance between 1ohm and 10kOhm.
- Input impedance is 10Mohm on DC, but only 1.1Mohm on AC with AC coupling (The 10Mohm DC resistance still applies).
- Frequency input is similar to AC input.
- DC ranges below 12V can be set to high impedance.
Current
- 3A and lower ranges is protected with a 3.15A/250V 5×20mm glass fuse accessible from outside.
- 3A and lower ranges is also protected by a 3.6A/1000V 10×38mm fuse inside the meter.
- 10A range is protected by a 11A/1000V 10×38mm fuse behind a lid.
Ohm, Continuity, diode and capacitance
- Ohm needs about 0.2s to measure 100ohm in default configuration.
- Ohm is up to 12.9V open and 10.0mA shorted
- Continuity is very fast (Less than 4ms) because it uses 4½ digit mode.
- Continuity beeps when resistance is below 10ohm, this is adjustable.
- Continuity is 9.3V open and 1.0mA shorted
- Diode range uses 9.3V, max. display is 7.0V at 1.0mA, max. current is 1.0mA shorted (Current is adjustable).
- 10uF takes about 0.3 seconds to measure in default configuration.
- 100uF takes about 0.4 seconds to measure in default configuration.
Miscellaneous
- Power consumption when on is 22 watt
- Power consumption when off is 5.7 watt
- There exist a multiplexer card with 10 inputs, it uses the rear inputs on the meter.
- The meter reach final value in one to two readings.
- Viewing angle is good.
- Display update speed depends on settings.
- Maximum measuring speed is 21000 reading/seconds and 1000000 readings/second using digitizer function (16 bit resolution)
- Measurement are always stored in a internal buffer, this can be presented in various ways, saved to a usb key or downloaded.
- The fan is fairly quite.
- Weight is 4580g including bumpers.
- Size is 390 x 225 × 100mm including bumpers.
Probes
- Probe resistance 33mOhm for one.
- Probe wire is very soft and 116cm long.

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A look at the capacitance measurement waveform.

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The number of digits in all ranges is adjustable, table covers the default setting.
Many other aspects of the meter can also be adjusted, it is even possible to add new function with the programming language (Keithley has a free program to add auto-hold to the meter).

Software

Software uses NI-Visa and some Microsoft libraries. It would not install on my usual test computer, but I could install it on my main computer.

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When started it shows a full screen picture with the found instruments at the left.

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Clicking on the DM6500 shows two possibilities, but in reality there was only one.

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The data logger only works with a multiplexer card in the meter.

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The meter shows a value and settings for this mode.

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Selecting temperature will change the available settings. The actual format with the boxes is fixed and in a smaller window scroll bars will be added.

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The same with the digitizer function.

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It is also possible to see a list of data.

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Or a chart with the data.

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There is cursors and it is possible to zoom in/out.

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The export function has some options.

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The data format is a standard CSV file and in European format (It probably ask my computer what to use).

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The image is in PNG format and is the data without much else.

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The software is not free, but it is possible to try it for a limited time.

License and extras

With expensive meters you often have to buy extra stuff to get full functionality, here they are:

Scanner card. A 10 channel scanner or 5 channel with 4 terminal connections or a 9 channel thermocoupler card with build in compensation.
Communication interfaces. USB and LAN is included, all other is extra, there are 3 different cards (Only one can be used at a time).
TSP link that is an interface to other Keithley equipment, this also requires a communication interface.
PC software.

Tear down

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The meter is easy to open, just four screws and the lid comes off.

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The fan supplies air below the circuit board

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And the exhaust is also below the circuit board.

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HS1: 36.2°C
I wondered if the high standby power is used to keep the reference warm. In this photo the meter has been on standby in about half an hour. The heat is from below the circuit board, it do not look like anything is powered on the board.

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M1: 54.5°C, HS1: 56.8°C
Turning the meter on and waiting another half hour, now some chips are warm, including the reference (M1).

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HS1: 57.1°C
Here is a closeup of the reference.

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It was a bit tricky to get the circuit board out.
Below the circuit board is two mains transformers, the rear panel inputs, the box for the scanner card and the fan.

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The circuit board that connects to the scanner card has two chips and also the connector for the fan.

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The rear side current input has the 10A circuit, the shunt resistor is on the rear circuit board. Connection from this circuit board to the main board is a ordinary flat cable.

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An area on the circuit board is covered by a metal shield.

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On this side their is not much below the metal shield. There is many areas on the circuit board with guard rings (A golden track around an area), this is done to avoid leakage current across the circuit board, the guard ring will usual be at the same voltage as the sensitive area, but driven from a low impedance source.

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The large white switch is to change between front and rear terminals, next to it is some input resistors, relays and protection circuit, behind it is some more relays and the highly sensitive area where the ADC must be (It is usually covered by the shield).
There is two ADC in this meter, one high precision and one fast for the digitizer, they may be chips or build from other chips and controlled from the FPGA.
The microprocessor is on the front panel and the part of the circuit board that connect to it is isolated from the analog and ADC parts.

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The front panel has two processors (U1 & U13: 2xMPC5125) and a LAN interface (U41: SMSC8710A) and a battery for the real time clock.

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Higher resolution pictures of the circuit board

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Conclusion

This is Keithleys cheap new generation bench multimeter. For high end bench meters it has the usual ranges and a little bit more, charting and tables is also common and the same for communication with the possibility for complete remote control, but where it is special is the extremely fast digitizer, the ability to load programs into it and the slot for a multiplexer that means the meter measure at 10 points more or less simultaneous (Within a few seconds).
The digitizer is sometimes very useful to check and measure pulses and variations in signals and compared to a oscilloscope the meter is much more precise (But the frequency range cannot match a oscilloscope).

Compared to a high end handheld DMM it is maybe double up but can do a lot more as long as it is on a bench and works very well together with a computer.

Notes

The software in this type of meters is fairly complicated and will have some bugs, I found a few during my testing and reported them to Keithley (It is easy to do software updates).

Keithley has 3 bench multimeters with similar design:
DMM6500 6½ digit with space for a small multiplexer.
DMM7510 7½ digit
DAQ6510 6½ digit with space for two large multiplexers.

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DMM HoldPeak HP-770D

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This is a DMM with 40000 count display and lot of functions.

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It arrived in a universal HoldPeak cardboard box.

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Inside the box was a pouch with everything inside.

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It included the DMM, a pair of probes, a thermocoupler, a instructions sheet and the pouch.

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No tip covers on these probes that is rated for 1000V Cat III and 20A
This means the rating is wrong.

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The plug is fully shrouded.

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The thermocoupler is encapsulated, this makes it usefull for inserting in stuff, but not as good for measuring surface temperatures.

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Using the tilting bale I was a bit worried about it breaking, after some time it got a bit more loose.

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There is a small light in the range switch.

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The sleeve do not give much protection agains bumps.

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Display

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The above picture shows all the segments on the display.

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Display during normal usage, it will show selected range and value.

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Voltage detector shows dashes depending on the strength of the electric field. It will also beep and turn on a red led while there is a field present.

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At the top is two leds used for the NCV, green when no field detected and red when a field is detected. The center position is a photosensor used to turn on the backligh on the display and the light in the range switch.

Functions

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Buttons:

Select: Select between AC/DC and different function for ohm settings.
Range: Will disable auto range and change range, hold down to activate auto range.
Rel: Shows values relative to current value, will also select manual range. Press again to disable.
Hz duty: Shows frequency and duty cycle in AC and frequency ranges.
Hold: Freezes the display.
Max/Min: Captures maximum/minimum values, will show min/max, requires repeating pulses to capacture the full value.

Rotary switch:

Off: Meter is turned off
A: Current AC and DC. In AC the Hz button will show frequency and duty cycle.
mA: Current AC and DC. In AC the Hz button will show frequency and duty cycle.
uA: Current AC and DC. In AC the Hz button will show frequency and duty cycle.
hFe: Transistor tester.
°C/°F: Temperature, will show internal temperature when no probe is connected.
NCV: Non contact voltage or electric field detection.
Hz: Frequency, use Hz button to select duty cycle.
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mV: Show DC or AC mV. In AC the Hz button will show duty cycle.
V: Show DC or AC Volt. In AC the Hz button will show duty cycle.
Off: Meter is turned off

REL and MAX/MIN turns off auto ranging.

Input

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20A: High current, maximum is 20A for 10 seconds.
mAuA: The lower current ranges and temperature.
COM: The common terminal for all ranges.
xxx: All other ranges.

The shutters secures that only the correct inputs are accessible.

Measurements

Volt and frequency
- Frequency counter (Range Hz) will count as long as the voltage goes within 1V of COM positive or negative.
- At 1Vrms frequency input range is 0.9Hz to 19MHz
- Frequency is always auto range
- Frequency counter and duty cycle can only be selected in AC ranges.
- Duty cycle works from 30% to 70% at 100kHz with 2Vpp, precision is within 1.6
- Duty cycle works from 1% to 99% at 100kHz with 4Vpp, precision is within 0.1
- 1 VAC is 5% down at 5.0kHz (RMS will not work at the frequency).
- Min/max is about 360ms to capture a value (It require that the peak repeats).
- Input impedance is 10-11Mohm on DC and AC including mV
- mV DC/AC input impedance drops to 2kohm above 2V
- Frequency input is 3-6Mohm below 2V above it drops to 2kohm.
- Rated overload protection is 100VDC and 750VAC
Current
- Frequency counter and duty cycle can only be selected in AC ranges.
- Fuse on uA/mA is 500mA/500V 6.3×32mm
- Fuse on A is 20A/500V 6.3×32mm
- mA range has audible alert when current is too high
- 20A for up to 10 seconds.
Ohm, Continuity, diode and capacitance
- Ohm needs about 3s to measure 100ohm
- Ohm is 1.0V open and 0.39mA shorted
- Continuity is moderate (About 110ms).
- Continuity beeps when resistance is below 62ohm.
- Continuity is 1.0V open and 0.39mA shorted
- Diode range uses 2.7V, max. display is 1.9999V at 0.4mA, max. current is 1.5mA shorted
- 11000uF takes about 9 seconds to measure (A too low value is shown af 5 seconds).
- Rated overload protection on is 500V DC/AC
Miscellaneous
- Current consumption of meter is 1.4mA in DC and 5.3mA in AC ranges(9.5mA with backlight in AC)
- Meter works down to 2.4V where it will turn off, battery symbol show at 8.0V.
- Reading are stable down to 3.5 volt, below that it will increase the reading significantly (40% above at 2.5V)
- Backlight brightness starts to drop at 4.5V and is dim at 3.2V
- Backlight has a significat hotspot where the led is placed.
- Viewing angle is good.
- Display updates around 5 times/sec
- Bargraph works at same speed as the numeric readings.
- The meter usual need a couple or more display update to reach the final value.
- Backlight is controlled by ambient ligthning, i.e. it turns automatic on.
- Will automatic turn power off in about 15 minutes (Holding SELECT down during power on to disable).
- Standard probes can be fully inserted.
- Weight is 355g without accessories, but with rubber sleve and batteries.
- Size is 194 × 88 × 44mm with rubber sleve and battery.
Probes
- Probe resistanse 42mOhm for one.
- Probe wire is soft and 100cm long.

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A look at the capacitance measurement waveform when measuring 1uF.

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Frequency input resistance.

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Manual list 9999 is maximum in capacitance and frequency, that is not correct.

Tear down

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I had to remove two screws to open the DMM.

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The circuit board is shaped to fix exactly.

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6 screws and I could remove the circuit board. I did also remove the screws for the input terminals, but that was not necessary.
There is a light pipe at the center of the range switch.

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The range switch has a track to control the shutters. The click uses small steel balls, they had a tendency to pop out when removing the circuit board!

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On this side of the circuit board is the transistor tester socket, the display, the two leds and a LDR (Light sensitive resistor) in addition to the pads for the switches.

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I had to remove 5 screws to get the display free.

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And there is nothing under the display, except from some soft stuff to prevent the backlight from rattling.

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The 20A shunt has a oops wire to the fuse, the track was obvious not enough. The uA and mA shunts are the two MELF resistors (R14: 99ohm, R15: 0.99ohm). The diodes (D1, D2, D3, D4) is protection of the current shunts. There is a led in the center of the range switch.
For protection of ohm and other ranges there is a small PTC and two clamp transistors (T3 & T4). It looks like a diode (D5) protects the meter agains wrongly connected battery. There is a 3.0V supply (IC4: 7530) and a reference (IC5: LM385-1.2).
The meter frontend (IC2: HY3131 50000 count DMM chip) with a processor (IC1: HY11P14) and a parameter memory (24C02N).
The NCV antenna is a metal strip soldered in the circuit board. It uses two high impedance resistors (R47 & R48: 2×100M, R49 is only 10Mohm) to control the potential on it.

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Conclusion

As usual on cheap(er) DMM’s the CAT rating is wrong, meter cannot be rated for 1000V and use 500V fuses. The transistor tester may also be problematic.
I like the high resolution, but it only increase precision on VDC, all other ranges do not have higher precision, only higher resolution.
The shutters reduces the risk of mistakes when switching between voltage and current, it is a good safety feature. The non standard sequence of input terminals are not.
The meter has a very good selection of ranges, but some more advanced functions is missing (Like average and peak).
Display updates are fast, but that do not make the meter fast, it is rather slow.

Notes

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DMM Siglent SDM3045X

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This is a low end bench meter, but it has many of the function of a high bench end meter, but not the resolution.

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It arrives in a big very solid cardboard box with the DMM well protected inside.

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It includes the meter, a quick start guide, a calibration certificate stating that the meter is in calibration, mains cable, a pair of probes with alligator clips and a usb cable. It do not include any manuals, they must be downloaded.

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Standard probe, with good safety.

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The plug is fully shrouded.

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Isolated alligator clips to mount on the probes.

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The front has the display, the buttons and the input.

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There are vent holes on the sides, but the meter do not have a fan.

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The meter can be tilted in two different positions.

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With the handle at the front the meter is ready to be carried.

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The back, there was a warning to check the mains voltage.

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The input fuse is on the back of the meter.

Display

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This meter is a computer that needs some time to boot and do self test, during that time it shows the brand name. Total time is about 16 seconds.

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Typical display when measuring without any of the more advanced stuff activated. Here I am measuring a voltage.

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Secondary display enabled and showing frequency. Many function on the secondary display will mean a relay has to change mode of the meter. Any combination of VDC/VAC/IDC/IAC can be shown on the main/secondary display, the ACV can also be combined with frequency or period.

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A bargraph can be enabled, it is possible to configure endpoints.

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The statistic can show max/min/average and a bit more.

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It is possible to show data as a chart.

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Or as a histogram with up to 400 bins.

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The collected data can be saved to usb, but it requires a number of button presses:
Utility, Store/Recall, Store settings, Browse, arrow down, Select, Type, Store Data, Yes, Done.

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There is also a help system build into the meter.

Functions

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DCV/DCI: DC voltage and current.
ACV/ACI: AC voltage and current
ohm 2W/4W: Resistance in either two or four wire mode.
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Temp/Scanner: Temperature with either a thermocoupler or PT100 sensor.
Dual/Utility: Select dual display measurement and save/configure/test/update.
Acquire/Help: Set trigger and look in build-in manual.
Math/Display: Statistic, Limits, DB, relative, bargraph, chart, histogram selections.
Run/Stop: Select to measure or not.
Single/Hold: Trig a single measurement and enable auto-hold mode.
Shift/Local: Access all the blue functions and cancel a remote connection (Local only need a single press on the key).
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Clik here to view.: Selection and adjustment in various menus.
OK: Confirmation of selection in menus.
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Clik here to view.: Change between auto range and manual range and select range.

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The 6 keys below the display are soft keys and the actual function will be listed on the display.
The power button is a soft switch, this means part of the meter is always on and using power.
A short press will turn the meter on a longer press will turn it off.
The led below the button is steady green while on and slowly flashing when meter is off.

Input

The inputs are only CAT II 300V rated, i.e. the meter is not designed for industrial and service on electric installations.

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HI: The voltage, frequency, capacitance, diode and ohm positive input.
LO: The voltage, frequency, capacitance, diode and ohm negative input.
HIsense: Four terminal ohm.
LOsense: Four terminal ohm.
10A: Current input

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The trigger in input, this is on of the conditions that can be used to start a measurement. The VM comp will signal when a measurement is done.

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The usb and lan connections on the back can be linked to a computer for remote control and logging.

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There is also a usb connector on the front, it can be used with memory sticks for saving data and configuration.

Measurements

Volt and frequency
- At 100mVrms frequency input range is from 2Hz to 500kHz
- Frequency counter has a capacitor at the input and ignores any DC offset.
- 1 VAC is 5% down at 320kHz, rms will not work at this frequency
- Period is 1/frequency, it do not show high/low period time.
- Min/max captures in about 200ms on slow speed and 15ms in fast speed, but peak must match sample window.
- Min/max is based on normal measurements, there is no special mode/circuit to make faster captures, this is standard for bench meters.
- Meter can show dB with adjustable reference either measured or entered.
- dBm reference impedance has these settings: 50, 75, 93, 110, 124, 125, 135, 150, 250, 300, 500, 600, 800, 900, 1000, 1200, 8000,
- Input impedance is 10Mohm on DC, but only 1Mohm on AC with capacitor coupling.
- Frequency input is similar to AC input.
- mVDC range can be set to high impedance.
- The VDC range will toggle a relay, even when not changing range. This may reduce reading speed significantly!
Current
- Current range is protected with a 10A/250V 5×20mm glass fuse accessible from outside.
- There is also a internal 12A/250V 5×20mm ceramic fuse for protection.
- uA range has very low burden voltage, it do not use the common 100ohm shunt.
- Auto range will disconnect shortly when changing from 6mA to 60mA range and 600mA to 6A range.
- Even in manual range the meter will auto range when a current range is overloaded.
Ohm, Continuity, diode and capacitance
- Ohm needs about 2s to measure 100ohm in default slow and about 0.3s on fast.
- Ohm is up to 5.0V open and 1.0mA shorted
- Continuity is quick (About 30ms).
- Continuity beeps when resistance is below 50ohm, this is adjustable.
- Continuity is 5.0V open and 1.0mA shorted
- Diode range uses 5.0V, max. display is 4.000V at 1.0mA, max. current is 1.0mA shorted (Max. display is adjustable from 0 to 4V).
- Diode range maximum is adjustable, it follows selected threshold, i.e. with 2V as threshold meter will maximum show 2V (Silly).
- 10uF takes about 2.5 seconds to measure.
- 9700uF takes about 14 seconds to measure.
Miscellaneous
- Power consumption when on is 9 watt
- Power consumption when off is 3 watt
- The meter reach final value in a few updates, extra updates is required when doing auto range.
- Viewing angle is good.
- Display update speed depends on settings (5, 50, 150 / second)
- Bargraph updates will follow the display update, this is normal for bench meters.
- At 150 readings/second the resolution will be reduced to 3.5 digit.
- The last 10000 measurement are stored in a internal buffer, this can be presented in various ways, saved to a usb key or downloaded.
- Weight is 3820g including bumpers.
- Size is 300 x 260 × 110mm including bumpers and handle.
Probes
- Probe resistance 26mOhm for one.
- Probe wire is very soft and 98cm long.

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A look at the capacitance measurement waveform.

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The mVDC range is fairly similar to handheld meters when in high impedance mode.

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The data format saved to usb in very simple, no time, mode or anything, just the values.

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High AC voltage can make DCV show to low value. AC input is capacitor coupled and will not be confused by DC.
The meter has trouble measuring close to 10000uF, it frequently shows overload.
When measuring 10Mohm resistance I can change the result 1Mohm by touching the cables (Using slow speed).

Software

This software is a free download from Siglent.

According to the installation manual you have to download and install NI-VISA yourself before installing this software, I already have this software on my test computer in the newest version and did not do anything.
The software is obvious for all Siglent bench multimeters and have lot of function for a meter with a multiplexer/scanner card, these are not relevant and do not work for this meter and I will not us them..

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Starting the software with the meter connected gives a complex looking user interface without much contents.

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Plugging the meter in and using “Add instrument” makes it possible to select the meter.

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Next time I start the software the meter will be listed and I only have to press connect. Once I had some problems that I could not start the meter after a connect, removing the meter and adding it again fixed that.

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Meter is connected and ready, press the start triangle and it is gathering data.

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Many of the meter functions are directly available here, but the check is not as stringent as on the meter, I could select dB for DC.
At the bottom is the statistic function.

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The bottom can also show the bargraph.

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Or a chart

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And the histogram.

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The temperature function with all selections from the meter available.

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It is possible to view the thermocoupler definition. The heading of the table is wrong, it is voltage (millivolt), not resistance.

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The gear button beside the meter display has some configuration, including local logging of data.

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When the software is running it will collect a local log, these can be viewed and saved.

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The saved data is a very simple format (The actual time format can be configured) and has the usual bug with point and comma. I will be very hard to read this data because comma is used both as a decimal point and as a delimiter.
The filename will match the meters mode, i.e. when measuring DC voltage the filename will include “DC Voltage(V)”.

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The viewing of the local logs also includes a chart

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Or a histogram. There is a lot of settings on this chart and the window can be resized.

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The chart can also be saved to disk or to clipboard.

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The “Control” button in the interface opens other ways to use the meter, here a direct SCPI interface.

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Fetching of screen dumps. This function is not synchronized with display updates.

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A virtual front panel.

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This interface can scale fairly well and the “DMM Explorer” window can be moved outside the main application.

Tear down

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Four screws at the back bumpers and one at the bottom then the lid was loose, but I also had to remove the handle (Turn it to the right angle and pull out), before I could pull the lid off.

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The front bumpers each has four screws, but it do not open anything up. It is probably for brackets that can be used for rack mounting.

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M1: 36.4°C, HS1: 37.2°C
When turned off it is only the transformer that uses power.

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M1: 55.3°C, M2: 46.5°C, HS1: 55.7°C
When on the processor and the +/-15V voltage regulators get a bit warm.

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The meter is in two parts, one for the transformer and one for the electronic. It is without a fan.

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At look down into the electronic section, it has two circuit board. One for the processor and one for the analog stuff.

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The mains input wires goes to a small circuit board together will all other mains wiring.

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The transformer has 3 output voltages, two for the analog board and one for the processor board.

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Back and front of the circuit board section. The connections from the front is soldered to the analog board.

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The two BNC on the back share a small circuit board that connects them to a flat cable.

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On this board is the processor (U1: AM3352 Arm Cortex A8), some flash memory (U4: MT29F2G08 2GB Flash) and a DDR RAM (U3: Marked SEC743/K481616/46IBCNA/YBE0270ZC) with a bus termination voltage controller (U15: LP2998). The last of the larger chips (U10: Marked 79CC91G3 / 83848KS0) is probably a network interface.
The power supply is a advanced power management chip (U2: TPS65910), a single switcher (U11) and some linear regulators (U12 & U14: L1117).

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The other side is mostly resistors and capacitors. There is also a large transistor (Q3) to handle the soft power on for the processor board.

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The analog board do not have any components on the bottom.

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The controller on the analog section is a Lattice PLD (U1: LCMX0640C-3TN100C 640 LUTs & 74 I/Os), it is connected to the processor board with a isolator (U201: ISO7641FC 3000V RMS isolation) and two optocouplers (U706 & U708: Cosmo K1010 5000 V RMS isolation). The analog converter (U511: AD7190 24 bit) is way better than this meter needs, the reference (U407: REF5025K 3ppm/°C) is also very high specification. There is support from some OpAmps and analog switches and +/-15V analog supply (U2 & U3: LM79L15 & LM78L15))
The input resistors are build from many resistors in series. The Sense input has 4 resistors (R301, R313, R314, R315: 4×29.9kOhm & R300, R310, R311, R312: 4×29.9kOhm) with diodes at the end (D300 & D301) for each terminal. There is also a 100kOhm input chain (R302, R303, R304, R305, R306, R307, R308, R309: 8×13K), the reason for that many resistors is probably power handling during overload and a 10Mohm chain (R73, R74, R75, R76>: 4×2.5Mohm).

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The input area has 5 mechanical relays for range selection. Below the white relay is the current shunts for 10A (R408: 0.01ohm) and uA/mA (R407: 1ohm) and a OpAmp (U300: TL072C). There is also the 1000 volt input capacitor, two MOVs and two spark gaps.
In addition to the fuse on the backside there is another one here, it is ceramic, but not a high voltage HRC fuse.

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Below the metal shield is OpAmps, analog switches and the RMS converter (U711: ES636 0.1%)

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Zoom in on part of the analog board, all IC numbers can be read here.

Conclusion

This is not a top end bench meter with “only” 4½ digit, but the meter works the same way as they do, with user interface, communication, relays/analog switches to handle all range changes. This meter is not a handheld meter with a mains power supply build in, but a real bench meter.
Generally the meter works exactly has expected, that means fairly good. I like that the current input is auto ranging from uA to A. The support for thermocouples is not present in all bench meters, but here it is, together with a minimum PT100 support (It is missing 3 & 4 wire support).
The software is good for a multimeter software and that it is free makes it even better.

I believe you get a lot of bench meter for the money with this meter, especially if you want to use the computer connection.

Notes

Siglent has 3 meters in this series:
SDM3045X: 4½ digit
SDM3055X: 5½ digit
SDM3065X: 6½ digit, can be ordered with a build in multiplexer.

The layout and user interface is very similar to Keysight meters

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Power supply frontend DPH5005-USB 50V/5A with Bluetooth and USB interface

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This device is the front end for a power supply, it must be supplied with low voltage DC power (Up to 50V).
Official specifications:

Input voltage range: 6.00-50.00V
Output voltage range: 0V-50.00V
Output current: 0-5.00A
Output power range: 0-250W
Product Weight: about 222g
Display module size: 79*43*38(mm) (L*W*H)
Cutout size: 71mm*39mm
Power module size: 93*71*41(mm) (L*W*H)
Length of connecting line: 200mm
Fixed hole center distance: 86mm, 64mm
Output voltage resolution: 0.01V
Output current resolution: 0.001A
Output Voltage accuracy: ± (0.5% + 2 digit)
Output Current accuracy: ± (0.5% + 3 digits)
Max allowable input current: 10A
Output ripple: 100mVpp

I got it from aliexpress store: RD official store

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It arrived in a styrofoam box together with some other stuff, inside the box was the plastic box with the electronic.

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There is a control unit, a power unit, two flat cables, the usb interface, the Bluetooth interface, cable for usb/bluetooth and a manual in English and Chinese.

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The control unit has a display, four buttons and a encoded that can be pressed.
The V and A buttons will enable adjustment of voltage and current with the encoder, press the encoder to select digit, when finished press V or A again.
Holding down V/A/SET will recall a preset, with V and A it is preset 1 and 2, with SET any of the 9 presets can be selected.

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Display while off and on, set point is shown at the top of the screen and input voltage at the bottom.

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There is a hidden communication menu, hold down the “V” button while powering on the supply to activate it (Default is fine for most applications).

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The front panel is made to be pushed into a rectangular cut-out

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The two flat cables from the power unit is connected at the back.

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Running at low input and output voltage, the output looks stable and the fan starts at 3.5A.

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Input voltage is too low for maximum output, due to limit on input current and the supply stops at 50V 2A, this also means about 20W is wasted as heat.

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With 24V input it can maintain 50V 5A output, there is still 17.5W heat.

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And with 50V input the heat is down to about 10W.

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With very low output current and voltage it can maintain output voltage down to about 6V input.

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High output voltage is also possible with low input voltage.

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With this low output voltage it can easily maintain output at 5A with any input voltage.

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It can handle 3A output with down to about 11V input, but this is a bit outside specifications, they say maximum input current is 10A and for that 16V input is needed. Output is stable until it cuts out.

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To maintain full output current at 50V it needs about 22V input.

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Current consumption depends on select output voltage and input voltage, but it is fairly low, even though it has to drive the display and the converts. With high output voltage it will use a bit more current to maintain the voltage.

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The power supply will go into constant current mode when overloaded, here I shorted the output and measured the current at 0.1A (The noise is probably due to the current resolution on my power supply).

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Here as a 5.1A constant current generator.

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When power is connected a small transient occurs on the output.

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The output turns on without any spikes.

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When loaded the output are slower to turn on and there will be some noise.

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Changing the load from 0A to 5A shows a significant temporary voltage drops.

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Changing the current from 5A to 0A do not show any voltage spikes.

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Both at low and high current there is some noise from the switcher on the output.

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The switcher is running at about 53kHz.

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It was no problem running at full output power for one hour.
After about 45 minutes I took the temperature photos below.

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M1: 69.3°C, HS1: 87.5°C

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M1: 64.7°C, M2: 60.9°C, HS1: 77.1°C

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The display is precise and there is very little change with load.

Specifications says the unit can be used as a charger, lets take a look at that:

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Power supply has input power, but output is off. A battery will be discharged with about 2.5mA, this is acceptable.

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Power supply is supplying 5V output, if the battery voltage is higher than the selected voltage it will drain the battery, again with about 2.5mA.
The charge current is not shown in this chart, it is below the 0 line.

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Power supply do not have input power, it will drain the battery with less than 1mA.
All in all it looks fine for charging.

Android application

Application will show an ad for another RD product when started.
Application is not on Google.
RD uses a file download service that opens ads in minimized windows.
Protocol is documented.

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Here I am connected and can adjust voltage and current.

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The wheel is used to adjust voltage and current with, but only two digits at a time. Touch the U_SET/I_SET and digits to select what two digits to adjust.

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The control panel is locked while using the phone and it is not possible to unlock it. I would have preferred that at least on/off worked.

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There is not many languages in the current version of the application.

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Using the file folder will save a Excel file on the phone with a fixed name, i.e. it is only possible to save one log.

PC application

Application is a 230MB download
Inside the archive is installation files
Application is very slow to install if it has to install the National Instruments part.
The screen is a fixed size (1062 × 619 pixels), there is no resize options.
RD uses a file download service that opens ads in minimized windows.
Protocol is documented.

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Program started, but not connected yet.

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When connected the actual values and curves are added. The dials can be changed with a mouse or new values can be typed in the numeric fields.

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The advanced tab where the presets can be configured and 3 types of automatic sequences can be defined and used.

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Here I have configured and started a “Voltage scan”.

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This can be viewed on the chart screen.

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And here with a oscilloscope.

A closer look at the electronic

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This side of the circuit board is only soldering, screws and some standoffs.

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All electronic is on this side. At the input is a 20A smd fuse (F3) and a high power mosfet (Q5). The buck switcher is a TL594. The microcontroller is a 32F100. The board do also have a internal switching power supply (U03: XL7005A) and some linear regulators. The output also has a 20A fuse (F1).

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The boost regulator (U3: LTC1871) is on a small circuit board

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Front panel

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The front panel uses four clips to keep the circuit board in the box.

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The circuit board has mechanical switches, a encoded and the display.

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There is nothing hidden under the display.

USB module

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The usb module uses a CH340 chip and two optocouplers.

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Bluetooth module

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The Bluetooth module is a Bluetooth module and a led.

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Conclusion

This module can deliver output voltage both below and above the input voltage, this makes is very flexible for input supply, but it need some power to deliver full output. The noise is a bit high and it has problem maintaining output voltage when load increase fast. The PC option may not be very nice looking, but it has some interesting functions on the advanced tab and I like the protocol is documented. The phone app has a very nice graphing and logging function, but adjustment of voltage and current is not that good.
This module is very useful to build a cheap bench power supply with. Add a cheap switching power supply, a box (RD sells one), some binding posts and some work.

Compared to professional units it is missing a lot: Lower noise, both numeric keypad and encoded, 4 terminal connections, larger display. But for the price it is very good and works fine.

Notes

The power supply was supplied by RD for review.

Other RD supplies I have reviewed:
Power supply frontend DPS5020-USB 50V/20A with Bluetooth and USB interface
Power supply frontend DPH3205 32V/5A with buck/boost converter
Power supply frontend DPS5015 50V/15A

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DMM WinApex ET8102

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This is a fairly cheap true rms multimeter.

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I got it in a typical cheap multimeter box, the drawing mostly match the meter.

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That was the meter, the probes, a thermocoupler and a manual.

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Probes are marked CAT III, but do not have the (partial) tip covers, this means they are CAT II.

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The plugs are fully shrouded, but the shroud is a bit short

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The thermocoupler is the standard cheap type with banana plugs, the cable is rather thin.

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The meter is not very heavy making it difficult to turn the range switch or press buttons without the meter moving around when on tilted.

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Display

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All the segments are shown during power on, but not all are used.

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Typical display during usage, it will show the number and selected measurement

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The NCV indicator, in addition to the bars the beeper will sound.

Functions

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Buttons:

Select (Yellow): Select DC/AC in current modes, continuity, diode, capacity, temperature in ohm mode and can also be used to show duty cycle in Hz mode and frequency and duty cycle in AC mode.
Hold: Will freeze the display reading, until pressed again, hold down to activate the background light.
Range, REL: Select manual range and change range, hold down to reactivate automatic ranging. In capacitance it is a REL function to zero out and offset.
Max/min: Capture maximum and minimum values, it will change between max/min/actual, holding it down will activate flashlight.

Rotary switch:

Off: Meter is turned off
VAC: AC voltage and frequency/duty-cycle, the frequency input has high sensitivity and low bandwidth.
VDC: DC voltage
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Clik here to view.: Ohm, diode, continuity, capacitance, temperature Fahrenheit, temperature Celsius
Hz: Logical frequency input, can also show duty cycle.
A: Ampere DC or AC
mA: Milli ampere DC or AC
uA: Micro ampere DC or AC
Test: Phase detection with one connection. This will show 0 or OL in the display, OL means phase detected.
NCV: Non-contact voltage or electric field detection.

Input

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10ADC: 10A DC current input.
COM: The common terminal for all ranges.
xxx: All other ranges, including uA and mA.

Measurements

Volt and frequency
- 1V AC readings is 5% down at 2.3kHz, rms will not work at that frequency
- AC frequency range with 0.1V input is from 1.1Hz to 2.5kHz
- AC frequency range with 0.1V input it can be stretched to 32kHz
- AC frequency range requires a zero crossing.
- Frequency input can handle +/-2.8V offset with 1Vrms input.
- At 1Vrms frequency input range is from 1.1Hz to 44MHz
- Duty cycle works from 1% to 99% at 100kHz with 4Vpp, precision is within 0.3.
- Max/min needs about 200ms to capture a voltage, autorange is disabled when using this function and it will not capture every max/min.
- Input impedance is 10-11Mohm on DC and AC
- Frequency input is 2-3kOhm in input impedance above 2V
- Input protection is 1000VDC/750VAC
- Frequency input is protected to 250V or 550V DC or AC peak (Both values are specified).
Current
- 10A range has audible alarm above 10A
- 10A range is fused with a 10A/250V 5×20mm fuse
- mAuA range is fused with a 0.6A/250V 5×20mm fuse
- Current ranges starts in DC
- Input voltage must not be more than 36VDC or 25VAC
Ohm, continuity, diode and capacitance
- Ohm needs about 2.5s to measure 100ohm
- Ohm voltage is 1.1V open and 0.25mA shorted.
- Continuity is fast (About 20ms).
- Continuity beeps when resistance is below 50ohm.
- Continuity is 2.1V open and 0.25mA shorted
- Diode range uses 4.0V, max. display is 3.3V at 0.25mA, max. current is 1.5mA shorted
- 10uF takes about 2.5 seconds to measure.
- 70000uF takes about 7 seconds to measure.
- Overload protection is 550V DC or AC peak
Miscellaneous
- Current consumption of meter is 1.6mA, 8.2mA with backlight, 9.1mA with backlight and 13.3mA with both.
- Meter turns off at 2.2V, battery symbol show at 2.3V.
- Readings will be correct until meter turns off.
- Backlight fades with dropping voltage, but it usable until meter turns off.
- Flashlight fades with dropping voltage, but it usable until meter turns off.
- Viewing angle is good except from the top.
- Display updates around 3 times/sec
- Backlight will automatic turn off after about 12 seconds.
- Flashlight will not automatic turn off, but turns off when the meter turns off.
- Will automatic turn power off in about 17 minutes.
- Standard probes cannot be fully seated in the meter, but they do connect (About 5mm stick up).
- The meter usual need a few display update to before it display the value.
- Weight is 209g without accessories, but with sleeve and battery.
- Size is 145 × 70 × 37mm with sleeve
Probes
- Probe resistance 46mOhm for one.
- Probe wire is soft and 73cm long.

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A look at the capacitance measuring waveform with a 1uF capacitor.

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The logical frequency input is about 2-3kOhm in input impedance.

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High DC voltage will block for AC readings.

Tear down

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I had to remove the sleeve and four screws to open the meter.

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The circuit board is not shaped like the enclosure, but is just a rectangle. The NCV bulb is empty, the antenna is only the circuit board.

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There was 6 screws holding the circuit board in.

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There is only a limited amount of parts on this side: The two fuses, a PTC for protection, the buzzer, crystal, capacitor and the flashlight led.
The two points marked SW1 & CAL is accessible from the battery compartment without opening the meter.

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The meter is on this side. The current input has a wire shunt for the 10A range and next to it the 1ohm and 99ohm for the mA and uA ranges, they are protected with a TVS diode (D3). The voltage input has the usual 10Mohm input made from two 5Mohm resistors.
The ohm range uses the PTC and a transistor pair (Q1 & Q2) for protection, but do also have a sense path through a small SMD resistor (R7: 1Mohm).
The NCV antenna is at the top of the circuit board and has a high ohmic resistor (R40: 22Mohm).

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Conclusion

As usual I do not believe the CAT rating, 250V fuses and a small SMD resistor on ohm input is not enough.
The meter looks very cost optimized, but it has a lot of functions, only mV is missing. The ohm position is rather busy with 6 selections.

Notes

This meter exist with many different names on it and small variations in functions.

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Olight i3E Eos with eneloop battery.

Victorinox Mini Champ.

Nite Ize Doohickey.

I have not found any triple A flashlight smaller than the Olight. Mini champ's bottle opener I can not master hence the doohickey. Unless I have a specific need for a larger flashlight or multi-tool this is my EDC. Anyone know of a smaller triple A?

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DMM Mustool MT109

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This is a smaller meter that has a lot of ranges.

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I got the meter in a brown cardboard box, the drawing mostly matches the meter.

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It included the DMM, a pair of probes, a thermocoupler and a manual.

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The probes has is rated for CAT III, but do not include the partial tip covers required for CAT III or CAT IV.

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The shrouded plug is the slightly short variety.

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A standard cheap thermocoupler.

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The range switch is a bit difficult to use single handed when meter is on the tilting bale, it slides around.

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There is a flashlight led on the front of the meter.

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Display

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The above picture shows all the segments on the display, not all are used.

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Typical display during usage, it will show the number and what measurement is selected.

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The NCV is the usual bars and the buzzer.

Functions

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Buttons:

Select (White): Select the ranges printed with yellow.
Hold: Freezes the display, hold down to turn off backlight (Display is not readable with backlight off).
Range/Rel: Will disable auto range and change range, hold down to activate auto range. In capacity mode it will zero the reading.
Max/min: Starts recording maximum and minimum value, press to select between max/min/disable. Hold down to turn the flashlight on/off.

MAX/MIN will change to manual range and return to auto range when disabled.

Rotary switch:

Off: Meter is turned off
VAC: Show AC voltage, using the Select button to select frequency and duty cycle.
VDC: Show DC voltage.
mV: Show mV, use Select to change between DC and AC
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Clik here to view.: Resistance, diode, continuity, diode, capacitance.
Hz: Logical frequency and duty cycle (Use Select to change between them).
A: Current DC and AC (Use Select to change between DC, AC, Frequency, Duty-cycle).
mA: Current DC and AC (Use Select to change between DC, AC, Frequency, Duty-cycle).
TEMP: Temperature, used Select to change between Celsius and Fahrenheit.
NCV: Non-contact voltage or electric field detection.

Input

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10A: High current input
COM: The common terminal for all ranges.
xxx: All other ranges.

Measurements

Volt and frequency
- At 100mVrms in VAC frequency range is from 1.3Hz to 6kHz
- At 2Vrms in VAC frequency range is from 1.3Hz to 60kHz
- VAC frequency range requires a zero crossing.
- At 0.1Vrms frequency input range is from 1.0Hz to 5MHz
- At 2Vrms frequency input range is from 1.0Hz to 65MHz
- The frequency input requires a zero crossing.
- Duty cycle works from 2% to 99% at 100kHz with 1Vpp, precision is within 0.3 (Mostly 0.1).
- Max/min needs about 500ms to capture a voltage with repeating pulses.
- 1 VAC is 5% down at 2.1kHz (RMS will not work at the frequency).
- Input impedance is 10..11Mohm on DC and AC
- Frequency input is above 1Mohm up to around 1.5 volt, then the protection clamps to 2kOhm
- Overload protection on DC is 1000VDC and 750VAC peak, except mV range is 550V DC or AC peak.
- Overload protection on AC is 750V rms
- Overload protection on frequency is 550VDC and AC peak, but meter may be damage at 250VAC peak (This is what the specifications says).
Current
- mA current is protected by a 0.63A/250V or 0.6A/250V 5×20mm glass fuse.
- A current is protected by a 20A/250V (Circuit board and manual says 10A) 5×20mm ceramic fuse.
- The A range has an audible alarm at 1A, i.e. beeper sounds all the time when current is 1A or above.
- The A range is slowly drifting when current is near 10A (About 0.6% in 30 seconds).
- The mA range has an audible alarm at 1A.
- Current ranges must only be used up to 36VDC or 25VAC
Ohm, Continuity, diode and capacitance
- Ohm needs about 2.8s to measure 100ohm
- Ohm is 1.0V open and 0.33mA shorted
- Continuity is fast (About 15ms).
- Continuity beeps when resistance is below 50ohm.
- Continuity is 1.0V open and 0.33mA shorted
- Diode range uses 3.2V, max. display is 3.000V at 0.1mA, max. current is 1.4mA shorted
- 10uF takes about 4.2 seconds to measure.
- 11000uF takes about 9.5 seconds to measure.
- 70000uF takes about 9.5 seconds to measure.
- Overload protection is 550V DC or AC peak
Miscellaneous
- Current consumption of meter is 32mA and 41mA with flashlight on.
- Meter “works” down to 2.1V where it turns off, battery symbol show at 2.3V.
- Backlight works down to about 2.6V, below that the display is unreadable, except with a bright light on it.
- Reading changes with voltage and 9V is down 6 count at 2.6V.
- Flashlight changes with voltage and works down to meter turns off.
- The meter usual shows the correct value on the first display update.
- Viewing angle is good, except from top.
- Display updates around 3 times/sec
- Flashlight can be manually turn on/off and will turn off when the meter turns off.
- Will automatic turn power off in about 180 seconds with a warning at 120 seconds
- When auto power off is disabled the meter will sound the buzzer at 120 & 180 seconds about every 15 minutes.
- Standard probes cannot be pushed fully down.
- Weight is 209g without accessories, but with rubber sleeve and batteries.
- Size is 145 × 70 × 37mm with rubber sleeve.
Probes
- Probe resistance 40mOhm for one.
- Probe wire is soft and 73cm long.

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A look at the capacitance measurement waveform.

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Frequency input resistance depends on input voltage.

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As usual mVDC has high input impedance at low voltages.

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Ohm specification goes to 60Mohm
AC voltage may show low voltage when large DC offset is present.

Tear down

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There where four screws holding the meter together.

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The circuit board is rectangular with most parts on the other side.

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Six more screws and the circuit board could be removed.

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This side has the fuses, the PTC, the buzzer, the flashlight led and the crystal for the multimeter chip, basically anything that needs some space in height. The mounted A fuse is a 20A fuse, but the circuit board is marked 10A. For the mA range a 600mA/630mA fuse is used, this is a bit low for a 1000mA range.
The two points marked RCAL2 is accessible from the battery compartment without opening the meter.

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At the bottom near the input connectors are the current shunts, 0.01ohm wire for 10A and 0.99ohm for mA, this resistor is a bit small for 1W. There is also two MELF resistors for voltage input (2×5Mohm). There a transistor pair (Q3 & Q4) for protection together with the PTC. As is usual the case with cheap meters safety is based on a single SMD resistor (R53: 900kOhm), that will be directly connected to the input terminal in some ranges.
The PTC and transistor clamp is used in all ohm and frequency selections.
THE NCV antenna is at the top of the circuit board.
The multimeter chip (Circuit board says HY12P65) has an external calibration memory (24C08N)

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Conclusion

As usual CAT rating is overstated with 250V fuses and a single PTC it will not handle CAT III 1000V or CAT IV 600V.
The meter is fairly nice with 9900 display, but there is some missing ranges and way to much noise from the buzzer when measuring ampere and the mA range cannot handle the rated current for long. The max/min is a nice function, but it is rather slow.

It is a nice meter for around the house or hobby usage, as long as it is only occasional usage, due to the fairly short battery lifetime.

Notes

The multimeter was supplied by Banggood for review.

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DMM Mastech MS8040

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This is a bench meter from Mastech. This type of bench meter is basically a handheld meter put into a bigger enclosure with a mains power supply added.

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The meter was shipped in its box, only wrapping was a layer of sticky tape.

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There was a lot of stuff in the box: The meter itself, a mains cable, a RS232 cable, probes, thermocoupler, adapter for thermocoupler, manual and a CD.

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Probes are branded with Mastech and has removable tip covers. The CAT rating is the usual II without covers and III & IV with covers.

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The plug is fully shrouded and standard probe plug size.

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The thermocoupler is standard type with standard thermocoupler plug (Except the pins are too long).

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With this type of thermocoupler plug a adapter is needed, this adapter can also be used for capacitors and resistors.

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The tilting bale only support one position.

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The meter is heavy and large enough that both the rotary switch and the buttons can be used by one hand.

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This meter can either use mains power or battery power and battery can be either 6xAA or one 9V.

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The meter has a handle one on side and a shoulder strap is also supplied.

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There is a lot of empty space inside the meter, some of it can be used to store accessories.

Display

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The above picture shows all the segments on the display. There is missing a icon for LPF (Low pass filter)!

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Typical display during usage, it will show the main number and what measurement is selected.

Functions

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Buttons:

Func (Blue): Select between the different modes on each position of the range switch.
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Clik here to view.: Turn background light on, this will automatic turn off again!
Range: Manual range selection, hold down to return to automatic ranging.
Hz %: Select frequency and duty cycle display in voltage and current modes, in frequency mode it will select duty cycle.
Hold: Freezes the display
Peak: Capture peak voltages
Max/min: Select max/min mode, press to toggle between max/min/current, hold down to disable again. To reset turn meter off for some time.
LPF: Enable low pass filter in voltage AC, the only indication it is activated is that the meter changes to manual ranging.
Rel: Shows values relative to current value
PC-Link: Enable data output, this will also disable auto power off.

Peak, max/min, LPF and Rel will all select manual ranging.

Rotary switch:

Off: Meter is off, but power supply is on
V: VDC and VAC, use FUNC to select DC or AC.
mV: Millivolt DC and AC, use FUNC to select DC or AC.
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Hz: Logical frequency, this range requires square wave input and will show duty-cycle (use Hz).
Off: Meter is off, but power supply is on
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Clik here to view.: Show voltage and current, used for external clamp. The clamp must be 1mV/A
Temp: Temperature input with thermocoupler type K.
uA: Microampere range, use FUNC to select DC or AC.
mA: Milliampere range, use FUNC to select DC or AC.
A: Ampere range, use FUNC to select DC or AC.

Input

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A: High current, maximum current is 10A
mAuA: The lower current ranges.
CON: The common terminal for all ranges.
xxx: All other ranges.

Measurements

Volt and frequency
- Frequency input can count 1Vrms with a DC offset of at least +/-8.5V
- At 1Vrms frequency input range is from 3Hz to 37MHz
- Duty cycle works from 5% to 95% at 100kHz with 2Vpp, precision is within 0.8.
- 1 VAC is 5% up at 38kHz (RMS will not work at the frequency).
- With LPF activates 1 VAC is 5% down at 650Hz
- LPF do not always activate when LPF button is pressed, check meter changes to manual (MANU) range when pressing button
- Max/min needs about 350ms to capture a voltage, turning it off will not reset captured value.
- Max/min can show max/min/current value
- Peak captures min and max values, it needs about 0.7ms to capture a voltage,
- Input impedance is 10-11Mohm on DC/AC
- Millivolt input impedance is high for both DC and AC up to about 3V where it drops to about 100kOhm
- Maximum voltage is not specified in manual, but meter says 1000VDC/AC.
Current
- Overload protection in uA and mA (Fuse 2): 0.4A/250V 6.3×32mm fuse (Manual says 0.3A)
- Overload protection in A (Fuse 1): 10A/250V 6.3×32mm fuse
- To replace fuses the meter must be taken apart.
Ohm, continuity, diode and capacitance
- Ohm needs about 1.4s to measure 100ohm
- Ohm is -0.4V open and -1.6mA shorted
- Continuity is very fast (About 1ms).
- Continuity beeps when resistance is below 30ohm
- Continuity is -3.0V open and -1.6mA shorted
- Diode range uses 2.8V, max. display is 1.8997V at 0.6mA, max. current is 1.8mA shorted, bargraph works up to 2.2V
- 70000uF takes about 11 seconds to measure.
- 10uF takes about 0.7 seconds to measure.
- Rated overload protection is 250VDC/VAC
Miscellaneous
- Power consumption from mains when off is 0.8 watt
- Power consumption from mains when on without background light is 0.9 watt
- Power consumption from mains when on with background light is 2.3 watt
- On battery current consumption of meter is 6mA to 7mA with backlight it is 42mA
- Meter works down to 3.4V where it turns off, battery symbol show at 7.5V.
- Below 4.5V on the battery, the readings will change very significant (About 40% when meter turns off).
- Backlight will fade with dropping battery voltage and is completely out at around 5.7V
- The display is usual correct on first or second update.
- Viewing angle is good
- Display updates around 2 times/sec
- Bargraph updates much faster than numbers (At least 15 times/sec)
- Backlight will turn off in 58 seconds
- Will automatic turn power off in about 15 minutes.
- Standard probes fits perfectly into sockets on meter.
- The transformer has a low level hum when on.
- Weight is 1300g without accessories and batteries
- Size is 237(width) x 233(depth) x 80mm.
Probes
- Probe resistance 20mOhm for one.
- Probe wire is soft and 81cm long.
- Communication cable is 191cm long

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A look at the capacitance measurement waveform.

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Frequency input resistance.

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DC millivolt input resistance.

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Display is a bit unstable in the high megaohms (10M+) and will not always be within tolerance.
A large DC voltage can block for AC voltage readings.
The VAC ratings are only valid from 20% of range, this is not very good.

Software

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The software is supplied including a RS232 cable, the files on the CD is dated 2008, but there was no problems installing in Win10. The program is called “Multimeter”, not the best name if you have more than one meter. Software support from COM1 to COM10, not perfect, but usable.

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When starting the software looks this way on a Windows 10 computer. Everything is in this view, there is no other screens (Except save and load dialogs).

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It can be maximised to fill the entire screen. The display shows actual value, a log and a chart, but the scale starts at +/-1000, this makes it rather difficult to see much.

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Using the left and right mouse buttons it is possible to zoom the chart in/out in this sequence:
1000-900-700-600-500-400-300-200-100-90-80-70-60-50-40-30-20-10-9-8-7-6-5-4-3-2-1
It requires some clicks to change the scale, but it works fairly well.

It is possible to save a “MAS” file, this is all data and can be loaded again to look at the data in this software.
There is also an “Export” option that saves in “xls” format. Excel will read the file, but do not show any data.

Tear down

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I had to remove four screws from the bottom of the meter to open it. It came apart in many parts with wires between some of them. Most wires has connectors and could be disconnected, but not all.

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After removing the screws, but before opening the meter, turn it around, then it is much easier to keep track of the parts.

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The top is empty, there are only the moldings for the storage compartment and the two batteries.

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The bottom has the power supply and more board.

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On the back is the mains inlet, the fuse, the transformer and the RS232 socket. The unconnected yellow wire is probably for 120VAC (i.e. swap yellow and blue (or red) for a 120VAC model).

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The power supply has a common mode coil followed by a bridge rectifier (D203, D204, D205, D206), then smoothing caps (C201, C248) and finally a 12V regulator (U213). After this the voltages from mains, 9V and 6xAA batteries are gated together with some diodes (D201, D202, D208) and goes to the meter circuit.
There is also two voltage regulator circuits one 3V (U202: 7530-1) and one 5V (U201: 7550-1), both supplied from the meter circuit. In this block is also a 1.25V reference (U3: LTQA->LT1790).
The last part of this circuit board is the RS232 interface, it is a led transmitter (D207) and led receiver (D234). The receiver is not powered and must draw its power from the RS232 connection.

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There is nothing on this side of the board.

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Most of the meter is in the front panel.

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The fuse board is mounted with two larger screws that is connected to the current terminals on the front and 3 smaller screws.

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The two diodes is 7V TVS diodes that is used to clamp voltage across the uAmA sense resistors (Fuse 2 is uAmA).

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I had to remove 4 nuts for the input terminals and 5 black screws before I could remove the multimeter electronic.

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6 more screws and the two circuit board could be separated

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This circuit board has a microprocessor (U304: ATMEGA8L) and two shift registers (U301, U305: 74HC595) probably as output extenders. My guess is that it do some adaption of the range switch codes.
There is also a thermosensor (U312: LM35D), this is probably used as cold junction compensation in the thermocoupler mode.

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I had to remove 6 more screws to remove the display.

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The current sense circuit on this meter is a bit special, it uses 3 resistors (R49: 9ohm, R48: 90ohm, R47: 900ohm) with bypass diodes on R49 (R1 & D2) and R47 (D3 & D4), this circuit gives a fairly high burden voltage.
The voltage input has 3 PTC’s and a 460ohm resistor for 4 input paths. There is 3 transistor pairs (Q1 & Q2, Q9 & Q10, Q14 & Q15) for protection in ohms and other sensitive ranges.
The range switch and the multimeter chip (ES51922A) handles most of the switching, but there is a single mux (U6: 4053). The two chips (U9 & U11:AD707J) is probably the RMS converter.

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The golden box is the voltage input resistor and reference resistors, there is capacitors on the back to give a fairly good frequency response.

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Conclusion

As usual on cheap meters the CAT rating is too high, with fuses rated 250V it cannot be a 1000V meter, but for a bench meter this is usual not very important.
The meter has good precision and lot of functions, but there is a few bugs (min/max do not reset) and some functions that do not belong on a bench meter (Auto turn-off of backlight and meter). The display is very good when the backlight is on, but it can be problematic to get enough light into it with backlight off and be careful not to blow the fuses, to replace them the meter must be taken apart. The computer software is not very useful with missing save functionality.

This meter is closer related to handheld meters than to professional bench meters, this do not make it a bad meter, just a bit limited compared to more expensive bench meters.

Notes

If I where going to use this meter I would hack the backlight to turn it permanently on (maybe at a slightly lower brightness).

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DMM Owon B35T

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Own has a couple of multimeters in this “35” series with some differences. The “B” models has Bluetooth, the “T” models has true RMS and the “+” model has memory for offline logging. I look at the model with Bluetooth and true RMS, but without offline logging.

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The meter arrived in a brown cardboard box with a minimum of text on it.

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Inside was a pouch with everything in it.

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The box/pouch included the meter, probes, alligator clips, a thermocoupler, transistor tester adapter, pouch, quick guide, specifications, QR code for link to app.

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Probes are marked 1000V 10A and the tip cover is marked CAT III, without the cover there is a CAT II marking.
The tip cover is screw on/off, the alligator clips are also screw on/off.

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The plugs has are fully shroud, but a bit on the short side.

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The transistor tester, thermocoupler, capacitor adapter. This way the transistor tester is safe.

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A cheap thermocoupler with banana plugs, but notice the black plug is on the red wire (There is a reason for that).

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I do not like the plastic for the battery lid, I have the feeling that it is a hard plastic that easily breaks.

Display

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The above picture shows all the segments on the display.
The meter do not use all segments.

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Normal DC voltage with voltage and bargraph.

Functions

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Buttons:

Select: Select between DC and AC and modes in the ohm position.
Range: Switch to manual range and select range, hold down to activate automatic ranging again.
Hz/Duty: Select frequency and duty cycle in AC modes and frequency mode.
Max/min: Capture maximum and minimum values, press to display one or the other, hold down to exit mode.
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Clik here to view.: Press to freeze/unfreeze current reading, hold down to turn on background light,
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Clik here to view.: Press to use relative mode (REL), hold down to enable/disable Bluetooth.

REL and Max/min disables auto range.

Rotary switch:

Off: Meter is turned off.
V: Measure DC and AC voltage, DC includes a mV range, in AC it is possible to select frequency.
mV: Millivolt range, has two mV ranges for both DC and AC, in AC it is possible to select frequency.
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Clik here to view.: Resistance, diode, continuity and capacitance
Hz%: Frequency, this support up to 10MHz.
hFE: Can check transistors with the supplied adapter.
Temp: Temperature.
uA: The uA range, in AC it is possible to select frequency.
mA: The mA range, in AC it is possible to select frequency.
A: The A range, in AC it is possible to select frequency.

Input

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A: High current, maximum current is 20A
mAuA: The lower current ranges and input for thermocoupler (Note polarity is reversed) and transistor tester.
CON: The common terminal for all ranges.
xxx: All other ranges.

Measurements

Volt and frequency
- Frequency input do not require a zero crossing
- At 100mVrms frequency input range is from 0.3Hz to 1.6MHz
- At 1Vrms frequency input range is from 0.3Hz to 14MHz
- Duty cycle works from 5% to 90% at 10kHz with 1Vpp, precision is within 5.7
- Duty cycle works from 1% to 99% at 10kHz with 2Vpp, precision is within 1.2
- 1 VAC is 5% up at 70kHz (RMS will not work at the frequency).
- Max/min needs about 200ms to capture a voltage, it may needs multiple pulses.
- Input impedance is 10-11Mohm on DC and AC, except mVDC that is high impedance
- mV in mV position has 10Mohm input impedance up to about 0.8V, then it drops to 100kOhm at 5 3olt and 2kOhm at 20 volt.
- Meter has two mVDC ranges, one in the V position and one in the mV position
- There is an audible warning when voltage is too high on mV (600mV) or V (750/1000V) range.
- Frequency input is 10Mohm up to 12 volt then it drops to 2kohm at 20 volt
- Rated overload protection on V is 1000VDC / 750VAC
- Rated overload protection on mV is 250VDC or equivalent AC
Current
- Overload protection in uA and mA: 1A/250V 5×20mm glass fuse
- Overload protection in A: 20A/250V 5×20mm ceramic fuse
- Measuring above 10A must only be performed for a short time.
Ohm, continuity, diode and capacitance
- Ohm needs about 2.9s to measure 100ohm
- Ohm is 0.64V open and 0.34mA shorted
- Continuity is quick (80ms).
- Continuity beeps when resistance is below 21ohm
- Continuity is 0.64V open and 0.34mA shorted
- Diode range uses 2.6V, max. display is 1.999V at 0.3mA, max. current is 1.2mA shorted
- 10uF takes about 2.7 seconds to measure.
- 4000uF takes about 30 seconds to measure.
- Rated overload protection is 250VDC or equivalent AC
Miscellaneous
- Polarity of temperature input is reversed, the plugs on the thermocoupler is also mounted reverse.
- Current consumption of meter is 2.3mA and 3.2mA depending on range (AC adds 0.5mA). AC with backlight is 20mA, AC with Bluetooth is 13mA (Everything together is about 28mA).
- Meter works down to 1.8V where it turns off, battery symbol show at 2.3V.
- The meter reading is stable at any battery voltage.
- Backlight fades with voltage and is very dim at 2.5V
- Bluetooth works until meter turns off due to low battery.
- Bluetooth cannot automatic recover a broken connection.
- The meter needs a couple of updates before the reading is fully correct.
- Viewing angle is good
- Display updates around 3 times/sec.
- Bargraph updates 30 times/sec
- Backlight will turn off in 47 seconds
- Will automatic turn power off in about 15 minutes
- Standard probes cannot be fully inserted into sockets on meter, but make connection, banana plugs can be fully inserted.
- Weight is 335g without accessories, but with batteries.
- Size is 185 × 88 × 45mm.
Probes
- Probe resistance 31mOhm for one.
- Probe wire is soft and 89cm long.

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A look at the capacitance measurement waveform.

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Frequency input resistance.

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Input impedance on mV range, on V range the mV input has high input impedance, but not here.

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The 40nF range has a -0.2nF offset, using REL the offset will be +0.2nF instead (The negative offset will only be visible as too low readings when measuring a capacitor).
Battery time is without Bluetooth, with Bluetooth it is around 200 hours.
Large DC voltage will block for AC readings.

Software Android

The Bluetooth phone software must be downloaded from Owon site and requires access to phone information, contacts, location and storage. I disabled the phone and contact access and the application still works.

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The software I got was V1.2.9 and I downloaded the Bluetooth 4 version. The program is called “MultimeterBLE” on Android.

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The typical meter display, the blue fields will activate buttons on the meter (it is still possible to use the button on the meter).
The microphone will enable English voice annotations of the value, the language is not perfect but understandable. The menu besides the microphone is used for meters with internal logging.
The software will only work in landscape mode.

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Here max/min has been activates, it is shown, but could have been more obvious.

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The software can support more than one meter, I only had one meter and have not tried this function.

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The logging mode, it shows a curve and a table, this data is also collected when showing the other display.
The chart has some problems: It do not change scale between mV and V, i.e. 600mV is shown as 600 and 2V is shown as 2 on the chart, this can occur in the same chart! This means it may be necessary to use the RANGE switch to get consistent charts.
I did not find a way to stretch the chart or table to full screen width. The chart and table will not reset if the range switch is turned, it will just continue to add data.

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It is possible to zoom in/out on the curve, either with the buttons in the gray area or with two fingers.

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On this screen the menu has function to save the data and share the saved data. I shared it with an email program and received the email on my PC.

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The settings can be used to adjust the sample interval and to set a time limit on how long to record the data. The “Fill” option will add a blue shading below the curve.

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The data is saved in a csv file using US format and without any headers, this means I cannot directly import it into Excel (I need to specify format each time).

The protocol is documented on Github and there is also a Linux program for communicating with the meter.

Tear down

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I had to remove four screws to open the meter

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The fuses have a cover on them, the 20A one has a bit heat damage from my 20A test.

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Five more screws must be removed to get the circuit board out.

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And four screws to remove the LCD display with backlight.

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The two fuses are rather small, but there is space for larger fuses on the circuit board, this probably means a meter bought from a EU distributor will have a large fuse. The 20A shunt (R38) is rather small, this is probably the reason for the time limit. The mA shunt is two resistor (R39 & R40: 2×1ohm) in parallel, one on each side of the circuit board. The uA shunt is the next resistor (R43: 49.9ohm). These resistors have about half the usual resistance, this is very nice for burden voltage. The uAmA shunts are protected by some diodes (D11, D12, D13, D14),
The voltage input has two paths, both with a PTC (R50 & RT1: 1kOhm), the main voltage input goes to two resistors, bypassed with two capacitors and a resistor (R22 & R33: 5Mohm, C45 & C49 & R80: 100kOhm). This improves the frequency response. The ohm range uses two transistor pair for protection (Q3, Q4, Q5, Q8), together with the two PTC’s. Frequency uses one transistor pair (Q4 & Q5).
I expect many of the diodes is used to encode the range switch for the multimeter IC.
The main meter IC is from Semic (U1: CS7729CN-001) with an external RMS converter (U10: AD8439JCPZ). The Bluetooth interface is a module (Chip is CC2541).
The meter has a couple of trimpots (V2, VR3, VR4, VR5, VR6, VR7) and a trim capacitor (C39).

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On this side is all the pads for the range switch, the buttons and the LCD connection. There is also one of the mA current shunt resistors (R40) and protection diodes (D12 & D14). The main voltage input resistor is two resistors (R22 & R33).

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Conclusion

As is often the case the CAT rating is way optimistic, 250V 20mm glass fuse do not belong in a 1000V CAT III meter. The lack of MOV’s and the small PTC’s without series resistor will also limit the ability to handle high voltage transients.
This meter has all the normal ranges for a competent meter and has a nice fast bargraph, but lacks any advanced functions. The input protection is fine for occasionally mains use. The lower shunt resistance (Burden voltage) in current ranges is nice, Bluetooth can be used for logging data at fairly short ranges

Notes

How do I review a DMM
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