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DMM UNI-T UT33A+

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This is a fairly simple and small DMM, but has a nice selection of ranges.

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The box is for all the UT33 meters with a checkmark for the actual model and a table on the back for comparing the models (in Chinese).
If you want all the function, you must buy all the models, none of them can everything.

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In the box was the meter, probe leads and a instruction sheet in both Chinese and English. The instruction sheet is for all four models in the series (A, B, C, D).

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The standard probes are about normal size, but rating them for 10A is on the optimistic side.

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The plugs are fully shrouded.

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With the meter lying flat it is possible to turn the switch, but on the tilting bale it will slide around.

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Display

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All the segments are shown during power on, not all are used by this meter.

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

Functions

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Buttons:

Sel/rel: Used to select AC in mV and current ranges and to zero capacity range.
Hold/Backlight: Will freeze the display reading, until pressed again. Hold down to turn backlight on.

Rotary switch:

Off: Meter is turned off
VAC: AC Voltage
VDC: DC Voltage
mV: Milli volt AC and DC, use SEL to select.
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Clik here to view.: Resistance range.
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Clik here to view.: Continuity range.
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Clik here to view.: Capacitance range, use REL to zero before measuring low values.
uA: Micro ampere range, use SEL to select AC.
mA: Milli ampere range, use SEL to select AC.
A: Ampere range, use SEL to select AC.

Input

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10ADC: 10A DC current input.
COM: The common terminal for all ranges.
xxx: All other ranges, including mA. It is always problematic when a current range shares connector with a voltage range, if the switch is in the wrong position the fuse will blow (at least). This will only affect current, voltage will still work.

Measurements

Volt and frequency
- 1V AC readings is 5% down at 2.5kHz
- Input impedance is 10-11Mohm on DC and AC
- Input protection is 600V AC/DC
Current
- 10A range is fused with a 10A/250V 5×20mm fuse
- mA range is fused with a 0.2A/250V 5×20mm fuse
- 10A range has an audible alarm at 10A or above.
Ohm, continuity, diode and capacity
- Ohm needs about 3.5s to measure 100ohm
- Ohm voltage is 1V open and 0.31mA shorted
- Continuity is fast (About 20ms).
- Continuity beeps when resistance is below 31ohm.
- Continuity is 2.1V open and 0.31mA shorted
- Diode range uses 2.2V, max. display is 1.999V at 0.07mA, max. current is 0.9mA shorted
- 2000uF takes about 9 seconds to measure.
- Overload protection is 600V AC/DC
Miscellaneous
- Current consumption of meter is 1.2 to 1.6mA (15.5mA with backlight).
- Display gets unstable about 1.6V, but it might show overflow before, battery symbol show at 2.4V.
- Readings will be correct down to 2.4V, below that they can be high or display can show OL
- Backlight works down to 1.6V
- Viewing angle is good, except from the top
- Display updates around 2.5 times/sec
- Backlight will turn off in about 30 seconds.
- Will automatic turn power off in about 15 minutes.
- Standard probes fits in the meter.
- The meter usual need a couple of display update to reach the final value.
- Weight is 208g without accessories, but with sleeve and batteries.
- Size is 135 × 77 × 47mm
Probes
- Probe resistance 72mOhm for one, that is fairly high.
- Probe wire is a bit thin, the are 89cm long.

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The meter is a true-rms meter.

Tear down

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I had to remove two screws, the battery cover could stay on.

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The circuit board is shaped to fit the box and uses ceramic fuses.

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I had to remove 3 screws around the range switch to get the circuit board out.

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And four screws to remove the lcd display, the backlight is soldered to the circuit board.

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There is no parts on this side, only pads for switches and lcd display and a marking of where ranges.

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The resistor for the uA range (R7: 99ohm) and uA range (R8: 0.99ohm) is protected by two diodes (D1 & D2: M7). The main input shunt is two resistors (R1 & R2: 2×5Mohm), there is also a secondary input chain (R4 & R5: 2X499kOhm). Ohm output is protected by a PTC (PTC1) and two transistors (Q1 & Q2).
The multimeter IC is a COP (Chip on board) that is bonded directly to the circuit board and then covered with some black stuff.

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Conclusion

The CAT rating do not match the fuses used, i.e. it is not correct, but at least it use fuses and fairly good ones.
The meter has a nice selection of ranges, but is missing frequency and min/max functions for a general purpose meter. This is the best meter in the UT33+ range, but the other meters in the range each has one function this meter is missing (Battery test, temperature, NCV).
I was a bit surprised that this meter is a true rms meter.

Notes

UNI-T do often make rebranded meters, i.e. it may exist with other names on it.

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DMM Innova 3320

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Innova has a couple of multimeters, this is their midrange model. They all have the probe holders sticking out to the sides.

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The meter comes in a blister pack with a comparison of the different meter models on the back.

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The pack includes the meter, a manual (That can also be downloaded) and probes.

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The standard probes a slightly on the small side and are rated for 600V CAT II like the meter.

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The plugs are fully shrouded and nearly standard probe size. They are interchangeable with standard probes.

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The range switch can be turned by one hand with the meter lying down or standing on the tilting bale.
The marking of “10MegOhm input” is a bit ridiculous, nearly all meters have that.

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The meter has an elastic strap on the back.

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It makes it slightly more difficult to use the tilting bale.

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But makes it possible to attach the meter to an arm, may be practical sometimes.

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The probe holders in function.

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Battery and fuse replacement requires opening the meter.

Display

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Nearly all the segments are shown during power on (The battery test symbol is missing).

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

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The battery tester has 3 leds in addition to the voltage readout, the leds are green, yellow and red and give a rough evaluation of the battery state. There is some light spill between the 3 position, but because the leds are different colors it is not a problem.

Functions

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This meter has no SELECT button and each range has its own position on the rotary switch.
Rotary switch:

DC10A: 10A and 2A DC current.
DC mA: All the lower DC current ranges.
12V: Battery test for 12V
9V: Battery test for 9V
6V: Battery test for 6V
1.5V: Battery test for 1.5V
Off: Turns meter off.
DC V: Shows DC voltage
AC V: Shows AC voltage
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AC mA: Two AC mA ranges.
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Input

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DC10A: This input is only used for two ranges: 2A and 10A DC.
COM: The common terminal for all ranges
xxx: All other ranges, including mA and battery test, it can be problematic to share current and voltage ranges on the same input terminal.

Measurements

Volt and frequency
- 1V AC readings is 5% down at 2.1kHz
- Input impedance is 10-11Mohm in V ranges
- mV has high input impedance.
- A high DC voltage may block AC readings.
- Input protection is 600V DC/AC
Current
- 10A range is unfused
- 10A range has an audible alarm at 10A or above.
- mA range is fused with a 0.315A/250V 5×20mm fuse
Ohm, continuity, diode and capacity
- Ohm needs about 3.3s to measure 100ohm
- Ohm voltage is 0.43V open and 0.2mA shorted.
- Continuity is moderate in speed (About 110ms).
- Continuity beeps when resistance is below 50ohm, but makes a bit noise up to 70ohm
- Continuity is 0.45V open and 0.2mA shorted
- Diode range uses 1.65V, max. display is 0.999V at 0.27mA, max. current is 0.7mA shorted
- Input protection is 250V DC/AC
Miscellaneous
- 1.5V battery uses 150ohm load.
- 6V battery uses 64ohm load.
- 9V battery uses 880ohm load.
- 12V battery uses 64ohm load.
- Battery ranges shares the mA fuse for loading and led, but not for voltage.
- Current consumption of meter is 0.9mA to 3mA depending on range (With battery test led on it is 10mA to 13mA).
- Meter turns off at 1.5V, battery symbol show at 2.4V.
- Readings are correct until the meter turns off.
- Viewing angle is good, except from the top
- Display updates around 3 times/sec
- Will automatic turn power off in about 15 minutes.
- Standard probes fits in the meter.
- The meter usual need a couple of display update to reach the final value.
- Weight is 186g without accessories, but with batteries.
- Size is 139 × 89 × 33mm (The 89mm in with is due to the probe holders, without them it is 74mm)
Probes
- Probe resistance 55mOhm for one½.
- Probe wire is 88cm long.

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Tear down

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To get into the meter two screws must be removed.

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There is a screw under a PTC, this is not a very good design.

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Four screws more and the circuit board can be removed. The pink zebra stibe that connect the display to the circuit board can be seen through the display lcd.

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The 3 leds for battery test and a few other parts are mounted on this side.

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The input has a PTC for protection in ohm ranges (besides the input terminal) and a glass fuse for protection of current and battery ranges.
There are 3 resistors for battery check 9V (R28: 150ohm), 1.5V (R29: 89ohm), 6V & 12V (R31: 60ohm). The the low current ranges are a 1 ohm resistor below the 10A current shunt.
I would expect that the Quad OpAmp (IC2: LM324) is the comparator that handles the leds. Input for voltage is two resistors (R23a & R23b: 2×5Mohm).
The meter has 3 trimpots to for calibration, one is probably for the battery tester.
I am not very impressed with the way the crystal is mounted, it is very close to touching R34 (The body of crystals is isolated from the actual crystal inside).

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Conclusion

The CAT rating is fairly low, but do not live up to modern standard with unfused ampere range and a 250V mA fuse in a 600V meter.
The meter is a fairly basic meter, but it has most ranges needed for general around the house or car work and in addition to that it has a easy to use battery tester, the leds makes it easy to decide how good a battery is (But watch out for the mA range, a battery in that range will blow the fuse). The meter is not for electronic or mains work. Precision is close to spot on.

Notes

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Gear Reviews

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A couple of weeks ago I was shipped a Fluke 365 Digital Clamp Multimeter from Fluke Corporation.

I was asked to simply use it however I wanted to. I could take it to work and use it there or just keep it at home and use it only when needed. Or I could do both and I chose both.

I have used it for something almost every day since it arrived.

I asked the representative if he would like an all-out testing and review or just casual use review. He stated very matter of fact “Tell me what you think of it, how you feel about the meter.”

I decided that I would do a brief review with the Specs some video footage (don’t worry not close to the long drawn out video like the 362 and the power supply). I have started getting some modern video gear and editing software so this one just shows some uses and showcases some of the features.

The Fluke 365:

Features and benefits

200 A AC and DC current measurement with detachable jaw

600 VAC and DC voltage measurement

Detachable jaw makes accessing wires and viewing the display easier

Built in flashlight/torch allows for easy illumination and identification of wires

CAT III 600 V

Compact design fits in your hand and can be used while wearing protective equipment

State of the art signal processing allows for use in noisy electrical environments while providing stable readings

Large, easy to read, backlight display automatically sets the correct measurement range so you do not need to change switch positions while taking a measurement

Three-year warranty

Soft carrying case

It also comes with:

Coated instruction card

Safety information sheet

Soft carrying case

TL75 test leads

Magnetic hanging strap

Five AA Alkaline batteries

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Accuracy:

Specifications

Diameter of measurable conductor 0.71 in or 18 mm max

Operating temperature -14 to 122ºF (-10 to 50ºC)

Storage temperature -40 to 140ºF (-40 to 60ºC)

Operating humidity < 90% at 10 to 30ºC, < 75% at 30 to 40ºC

Operating altitude 0 to 2000 m

Size 225 x 65 x 46 mm, (8.858 x 2.559 x 1.811 in.)

Weight 275 g, (10 oz.)

Temperature coefficient 0.01% ºC

(< 18ºC or > 28ºC)

Warranty Three years

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The 365 kind of falls into a mid-level meter among the very large line of Fluke meters. The average price seems to be around $230.00. This is not a budget meter it is however a meter that may well last you until retirement.

I have known people to have Fluke meters for 20 or more years. They are just that well made. Fluke does not accept quality issues of any kind.

The meter is compact and light. Simple to use with auto ranging and the clamp of course. I almost forgot to mention…. The clamp is removable… You have about 3 feet of wire connecting the clamp to the body of the meter. I love this feature.

In very cramped spaces it makes life so much easier. If you have ever had to repair industrial machinery then you can appreciate this feature very much.

Removing it does not seem to affect the accuracy at all.

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I have used several types and styles of clamp meters but this is the first one that it makes my job easier and much of the time more efficient.

I can without hesitation recommend this meter to anyone that is looking for a reliable, accurate, light weight detachable clamp for just a touch over $200.00…. Did I also mention it is a Fluke.

I hope you enjoy the video below. I tried to make it long enough to allow you to see the 365’s features but not so long that it became a motion picture.

It has been my pleasure to have been given the opportunity to review this meter.

http://en-us.flukhttp://en-us.fluke.com/products/clamp-meters/fluke-365-dc-clamp-meter.html#featurese.com/products/clamp-meters/fluke-365-dc-clamp-meter.html#features

The awards that I mention in the video and could not remember at the time are.

Award: Fluke 365

MOTOR Magazine Top 20 Tools Award
TechShop Top 5 Tools Award (Automotive)
Control Engineering, Engineer's Choice Award (This is an extremely hard awards to win)

Enjoy,

Terry

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Terry White

Skype terrywhite1@live.com

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Gear Reviews

DMM Brymen BM235

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Brymen is one of the good DMM manufactures and have a large selection of DMM’s in their program. This meter is a mid-range meter.

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The meter arrived in a red box with a feature list for their BM23x series of meters (BM235 is the best of them).

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The probes are rated for 1000V and 10A in CATIV environment, this is a very good rating and way better than the meter.

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The removable tip must be on for best safety.

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The plug is fully shrouded and full size.

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The thermocoupler has a single connector to the multimeter, that is considerable better than the two loose banana plugs and the general construction looks nice.

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The tilting bale is just about stable enough to change range and use switches with one hand. The switch is a bit on the hard side.

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Before it is possible to open the battery cover the sleeve must be removed.

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Both the 400mA and the 10A fuse is accessible from the battery compartment.

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Display

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

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

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The Low-Z range will automatic detect AC/DC and do not show any voltage before it can decide that.

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The electric field detection (NCV) shows from 1 to 5 bar depending on field strength. There are two ranges EF-L(ow) and EF-H(igh).

Functions

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This meter will remember what was selected with SELECT and start in the same function next time, power off will not reset this.

Buttons:

Select: Selects secondary ranges for each position on the range switch, hold down to turn on backlight.
Range: Switch to manual ranging and will also change range, hold down to get back to automatic, in NCV it will change between EF-H and EF-L
Rec: Starts recording min/max/avg. values, press the button to change between min/max/average/actual, hold down to exit.
Hold: Will freeze the display, hold down to use current value as reference and show all further readings relative to this.
Hz: Select Hz display
EF: Select electric field detection (NCV), the RANGE button can be used to switch between high and low sensitivity.

Rotary switch:

Auto V LoZ: Select Low-Z mode, work both for AC and DC, but is locked to 600 and 1000V range
Off: Meter is turned off
V: Show DC and AC voltage with an optional low pass filter (VFD) for AC, use SELECT for AC/VFD/DC and “Hz” for frequency.
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mV: Show DC and AC millivolt, use Select for AC and “Hz” for frequency. This is also the temperature range (Select again).
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mA A: Current DC and AC, use Select for AC and “Hz” for frequency.
uA: Current DC and AC, use Select for AC and “Hz” for frequency.

Input

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10A: High current, it can only withstand 10+ ampere for a short time (Fuse is 10A). Meter will select mA or A depending on where probe is plugged in.
mAuA: The lower current ranges, the selector switch will change between two different shunts (Fuse is 400mA, input is rated for 600mA).
COM: The common terminal for all ranges.
xxx: All other ranges.

Measurements

Volt and frequency
- Frequency input requires a zero crossing.
- Max/min needs about 310ms to capture a voltage.
- At 0.1Vrms input frequency range is from 3Hz to 270kHz
- At 1Vrms input frequency range is from 2Hz to 330kHz
- 1 VAC is 5% down at 1.6kHz, in VFD mode it drops at 260Hz
- VFD only works in 600.0 and 1000 volt mode and reduces bandwidth to about 100Hz for 1% precision
- Input impedance is 10-11Mohm on DC and AC, also in mV range.
- Low-Z is 10Mohm at low voltage, 8Mohm at 50VDC, at 230VAC it starts at 2kOhm, but will increase fast to 50kOhm
- Voltage ranges rated to 1100V AC/DC
- mV range rated to 1000V AC/DC
Current
- Ranges rated to 1000V AC/DC
- uAmA range is protected by a 0.4A/1000V 6×32mm fuse
- A range is protected by a 11A/1000V 10×38mm fuse
Ohm, Continuity, diode and capacity
- Ohm needs about 0.8s to measure 100ohm, this is very fast
- Ohm is 1.8V open and 0.16mA shorted
- Continuity is fast (About 20ms).
- Continuity will flash background light in addition to sounding buzzer
- Continuity beeps when resistance is below 161ohm
- Continuity is 1.7V open and 0.16mA shorted
- Diode range uses 3.2V, max. display is 3.000V at 0.025mA, max. current is 0.33mA shorted
- 1000uF takes about 7 seconds to measure (First estimate in 3 seconds).
- Ranges rated to 1000V AC/DC
Miscellaneous
- Current consumption of meter is 2.5mA(23mA with backlight)
- Meter works down to 1.7V where meter turns off, battery symbol show at 2.5V.
- Backlight fades with falling voltage, but works down to meter turns off
- Reading is stable until about 1.8V where it increase significantly (5.000V -> 5.206V)
- The meter need one or two display update to reach the final value.
- Viewing angle is good
- Display updates around 3 times/sec
- Backlight will automatic turn off in about 10 minutes.
- Will automatic turn power off in about 32 minutes.
- Auto power off will not be activated when meter is used.
- Standard probes fits perfectly.
- Weight is 335g without accessories, but with batteries and sleeve.
- Size is 162 × 81 × 53mm with sleeve.
Probes
- Probe resistance 27mOhm for one
- Probe wire is soft and 101cm long.

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A look at the capacity measurement waveform, it is non-polarized.

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Tear down

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I had to remove 3 screws to open it.

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Notice the two springs on the battery holder. There is also some plastic that goes between ground terminal and mAuA terminal.

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There is a lot of slits in the input circuit board.

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Input board has both wired (for 10A and mAuA) and connectors to the main circuit board.

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I had to remove one screw and desoldering two wires before I could remove the input board.

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Main circuit board is shaped like the meter and is mounted with a lot of small screws (6).

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Display uses a black zebra stipe for connection and two springs for backlight.

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One this side of the circuit board is all the switches and a resistor for the mA range. The other part is probably an inductor for the boost converter that supplies the backlight. There is also a 3 pin chip (U2: marked R11), I wonder if it is a reference. There is two EEPROM memories (U4 & U5: Marked L02, 6246W) for calibration and remembering last settings.
It looks like many of the transistors are used for protection, but there is also the backlight boost converter (Q13).
The antenna for the NCV is near J1 and is on both sides of the circuit board.

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Most of the meter is on this side of the circuit board. There is a DMM chip (U1: marked BTC J200, LP6A-0000, R780H.F) and a LCD driver chip (U3: HY2613C). The long black square resistor is the main input divider (10Mohm).
The 5 large diodes (D8, D9, D10, D11, D12) is protection for the mAuA shunt resistors. The uA shunt (R33: 100ohm) is placed close to the holes for the input terminals.

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The input board contains the four input connectors and some protection.
The two pink resistors (R30 & R38: 5Mohm) is for sensing if something is plugged in, they are also large enough that 1000V with a blow fuse will not do any damage. The resistors (R7 & R8: 1Kohm) are series resistors for the two PTC (PTC1 & PTC2), followed by 3 MOV’s (SPG1, SPG2,SPG3). All this limits the voltage and current that gets to the main board.

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Conclusion

This is a fully featured DMM with a few extra functions like NCV, average, VFD and Low-Z, but it is missing duty cycle. The idea about remembering the last selections is both good and bad, it means the DMM mostly will be in the desired function, but it also means I have to check the display for function each time.
As usual the burden voltage is bad in the high mA range. The UL listing probably means the CAT ratings are correct according to US standards.
It has one problem and that is the behavior when the battery is nearly empty, a good DMM must never show wrong value!

I will call this a good DMM to use for both hobby and professional usage.

Notes

This meter is frequently sold in more or less rebranded versions.
The EEVBlog sells this meter with a blue sleeve.

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DMM XB-866

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This is a cheap pocket DMM, it has the most common ranges, but do not have any functions.

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The meter arrived in a cardboard box that is designed for two models (The two sides are different models).

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The box contained the meter and a manual.

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The probes are part of the meter and cannot be replaced without soldering.

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The area around the batteries, the spring and lid is a bit cramped, making the lid a bit difficult to mount and unmount.

Display

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

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

Functions

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Buttons:

Select: Used to select between Diode and Continuity and to select AC in current ranges.
Range: Used to manually select range, hold down to return to auto range.

Rotary switch:

Off: Meter is turned off
VAC: Voltage AC
VDC: Voltage DC
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Clik here to view.: Diode and Continuity, use Select to change.
uA: Low current range, use Select for AC
mA: High current range, use Select for AC
Off: Meter is turned off

Input

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A red and a black probe is linked to the meter.

Measurements

Volt and frequency
- 1 VAC is 5% down at 2.2kHz
- Input impedance is 10-11Mohm in DC and AC
- mV DC is high impedance.
- At low AC voltage there is problems ignoring a high DC voltage.
Current
- uA and mA range is fused with a soldered fuse, that will prevent any range from working if it is blown.
- 2000uA and 200mA range will give audible alarm when overloaded
Ohm, continuity, diode and capacity
- Ohm needs about 3.5s to measure 100ohm
- Ohm is 0.42V open and 0.2mA shorted
- Continuity is slow (Up to 150ms, most of the time it is time considerable faster).
- Continuity beeps when resistance is below 48ohm.
- Continuity is 0.44V open and 0.2mA shorted
- Diode range uses 1.6V, max. display is 1V at 0.25mA, max. current is .67mA shorted
- The specifications says input are protected to 250V DC or AC
Miscellaneous
- Current consumption of meter is 0.8mA in VDC and 1.4mA in AC and current.
- Meter displays values down to 1.5V where it turns off, battery symbol show at 2.3V.
- Readings will change slightly, about 2 count on a 5V value.
- Viewing angle is good, except from the top.
- Display updates around 2.5 times/sec
- Will turn power of automatic after about 15 minutes.
- The meter usual need a few display update to reach the final value.
- Weight is 128g without accessories, but with batteries.
- Size is 118 × 75 × 21mm
Probes
- Probe wire is fairly soft and thin, they are 43cm long.

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mVAC must be manually selected.

Tear down

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Removing the battery lid also loosens the back and it can be removed, together with the lid.

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Four more screws and I could remove the circuit board, I had to be a bit careful with the battery connections.
The display do not have tight alignment control, this makes it a bit tricky to get the display/zebra stipe correctly aligned when putting it together again.

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Only the switch, buttons and LCD connections on this side.

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The green device (R36) is a PTC for input protection, the two resistors near it, but under the buzzer is the current shunts for uA and mA. The input voltage resistor is split in two (R2, R3: 2×5Mohm). The input clamp on this meter is probably D2 & D3. The meter has two trimpot for adjustment. Usual meters uses a crystal to get a stable frequency for the DMM chip, but in this case it is a resonator (It is cheaper).
It looks like the fuse is the first part on the input, i.e. a blown fuse prevents measuring voltage!

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Having the probe leds through a hole in the circuit board will improve the strength considerable.

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Conclusion

The meter is very small, but has many of the common ranges (Autorange helps with that). It works fine in the ranges it has and for a simple meter it is fairly good, but do not blow the fuse, it is soldered in.

Notes

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

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DMM Prova 903

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This is a very advanced meter from “TES”, it is supposed to be very precise and has two channels (That is two meters in one).

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The meter arrived in a cardboard box that is used for the two top models.

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The box included the meter, two probes, two wires with alligator clips, a computer interface, four manuals (English + Chinese for meter and software).

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Probes are unbranded and rated for CAT III 600V

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The plug is fully shrouded and standard probe plug size.

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Alligator clips do not have a CAT rating

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The plugs are stackable shrouded plugs, this makes it possible to share the common input terminal on the meter.

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

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The PC connection is here with an optical link.

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The rubber sleeve must be removed to replace the battery. Both battery and fuse is accessible with one screw removed.

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The screw stays in the lid (nice).

Display

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The above picture shows all the segments on the display. The meter use nearly all of them.

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This readout and the bargraph is for the large rotary switch and the V input terminal.

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The upper readout is for the small rotary switch and the V/mA input.

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When frequency and duty cycle is selected (Hz button or SHIFT to TTL mode) both displays are used, one for frequency, the other for duty cycle.

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Both range switches used, one on A and one on V. The triangle above CH1 shows what readout the button rows will affect, press CH2/CH1 to change to CH2.

Functions

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Buttons (Generally the buttons are rather slow to use):

Shift (blue): Select the blue modes on the range switches.
Range: Switch to manual range and select range, hold down to activate automatic ranging again.
Zero: Zero the value and show relative values, hold down to disable.
Hz: Switch to frequency and duty cycle mode in volt and current modes, this works for both range switches and for both AC and DC (It will switch to AC internally).
Rec: Start recording data, meter can only record one type of data and must be cleared before next logging session. Hold down to turn logging off again. If the button is held down during power on the recordings are cleared and it is possible to adjust the sample interval.
CH2/CH1: Use to select what channel the buttons works on
Max/min/hold: Freeze the display and starts recording min/max values, pressing the button will change between hold/min/max values (Bargraph will show actual value). Hold down to disable.

Zero, Rec and max/min/hold will all disable auto range.

Small Rotary switch:

Off: Meter is turned off.
VAC: Measure AC volt on the mA/V terminal
VDC: Measure DC volt on the mA/V terminal
mVDC: Measure mDC volt on the mA/V terminal
mVAC: Measure mAC volt on the mA/V terminal
Off: Meter is turned off.
A: Measure A current on the A terminal, use SHIFT to select AC
mA: Measure mA current on the mA/V terminal, use SHIFT to select AC
uA: Measure uA current on the mA/V terminal, use SHIFT to select AC

Large Rotary switch:

Off: Meter is turned off.
VAC: Measure AC volt on the V terminal
VDC: Measure DC volt on the V terminal
mVAC: Measure mAC volt on the V terminal
mVDC: Measure mDC volt on the V terminal, this is also the TTL frequency input.
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Input

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A: High current, maximum current is 10A.
mAuAmVV: The lower current ranges and + voltage input for the small rotary switch.
CON: The common terminal for all ranges and both inputs (Use the stackable alligator clip lead for one input).
xxx: All ranges on the large rotary switch.

Measurements

Volt and frequency
- TTL frequency input triggers around 0.8V and requires at least 1Vpp
- AC frequency input requires a zero crossing.
- At 2Vpp square wave input on TTL the frequency range is from 1Hz to 1.5MHz
- At 100mVrms input on mVAC range, frequency range is from 2Hz to 800kHz
- Duty cycle on TTL works from 2% to 99% at 100kHz with 4Vpp, precision is within 1.3 (Precision improves with lower frequency)
- 1 VAC is 5% down at 600kHz (RMS will not work at the frequency).
- Max/min needs about 200ms to capture a voltage.
- Input impedance is 10-11Mohm on VDC
- Input impedance is 5Mohm on mVDC main input and high on mVDC secondary input.
- AC input has a capacitor
- Rated overload protection on V ranges is 1000VDC/VAC
- Precision is only valid when one input is used, with two inputs it will be lower.
Current
- 10A range may be loaded to 20A for 30 seconds
- Overload protection in uA and mA: 1A/1000V 10×38mm fuse
- Overload protection in A: 20A/1000V 10×38mm fuse
Ohm, continuity, diode and capacity
- Ohm needs about 1.5s to measure 100ohm
- Ohm is 1.2V open and 1.05mA shorted
- Continuity is very fast (Below 10ms).
- Continuity beeps when resistance is below 50ohm
- Continuity is 3.3V open and 1.05mA shorted
- Diode range uses 3.3V, max. display is 2.0000V at 0.46mA, max. current is 1.05mA shorted
- 400uF takes about 5 seconds to measure.
- Rated overload protection is 1000VAC, no specification for capacitance range.
Miscellaneous
- Current consumption of meter is 8mA (Secondary display adds about 0.2mA)
- Meter works down to 4.4V where the display is faded, battery symbol show at 6.9V, but only if second channel is on.
- The meter reading will change from 6.0V, a 5V reading shows 6.6V at 4.6V battery voltage
- The meter usual needs two display updates before the reading is fully correct.
- Viewing angle is good
- Display updates around 1.5 times/sec with one reading on and 1 times/sec with dual readings
- Bargraph updates fast
- Will not turn power off automatic
- Standard probes fits perfectly into sockets on meter.
- Weight is 615g without accessories, but with sleeve and batteries.
- Size is 210 × 104 × 55mm.
Probes
- Probe resistance 54mOhm for one.
- Probe wire is soft and 90cm long.
- Alligator wire resistance 22mOhm for one.
- Alligator wire is soft and 80cm long.

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A look at the capacity measurement waveform.

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The high ohm ranges are very sensitive to noise and may jump a bit up/down.
Ohms values just above the maximum range (i.e. 40-60Mohm) makes the display freeze, higher values will show OL
In manual range all capacitor ranges can be used up to 9999.
Tolerances are only valid with on channel on, they are worse when both channels are used.

Software

The software and cable is included.

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The cable is an optical connection and uses a usb connector on the PC side. It is a CP2102 chip and a working driver was supplied on the CD. The software installs VISA drivers.

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The software can show the two channels and a math channel, both as digital, analog and curve, but no tabular display.
The above is with CH1 on.
It is possible to activate the button functions from the software.

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Here I have both CH1 and CH2 on and the math channel will be calculated.

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The sample rate can be adjusted and it is recommend to use 2 seconds or slower when logging both channels.

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The design of the curves can be adjusted in many ways, this adjustment menu is present for CH1, CH2 and MATH channel.

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It is also possible to select what the math channel do, at least to some degree.

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The CSV file is not a CSV file, each line start with a quote.

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Both dual display and math channel is logged when on.

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The meter can record data on its own and it can later be fetched with the software. When fetching data the software ask about when the data was recorded and will then add timestamps to the values.
This time I used the cursors to select a specific data point, the readout will show this value.

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The saved data looks like above, but the timestamp is based on the time I entered.
The meter can log for nearly 6 hours with a reading each other second.

The communication protocol is documented in the manual and is very simple.

Tear down

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The battery cover and two more screws must be removed to open the meter.

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There is some shielding with holes for IR communication in the back.

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The top circuit board takes up all the space inside the meter. The screws looks like they are connections to the lower circuit board.

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I had to remove 8 screws before I could get the circuit board out. The range switch bars can just be pulled off, but it is a good idea to get them on in exactly the same position and the right way around!

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The lower circuit board could just be pulled out.

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On this side is pads for the buttons on the front and a pair of protection transistors.

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Four more screws and I could remove the display, be careful with the orientation of it.

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Here is a HOLTEK HT49R70A-1 8 bit RISK processor with 8Kx16 program memory. It runs at 10MHz. There is als two EEPROM chips (U9 & U11: 24LC256 32Kx8), probably used for the 10708 dataset log.

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On the other side is part of the range switch and the fuses.

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This circuit board is the analog and converter board. On this side there is two PTC’s and a MOV near the V input terminal. The 10A shunt is very large (good) and the mA and uA resistors also looks fairly large.
The input mux (U3: DG419) that switches between the two inputs is partly hidden below the red wire. The large chip (U1: AD637) is the rms converter.

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On this side are two PTC’s more and a MOV, but they are not at the input terminal, instead the signal is wired halfway up the circuit board. It is interesting that one of the input resistors (R17: 10Mohm) has capacitors in parallel (This is done to improve the frequency response). There is both trimpot, but also trim capacitors and a switch (SWA in off position). It looks like some of the input protection is done with red leds. There is 4 diodes to protect the current shunt.
The number on the multimeter front-end chip is not visible.

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Conclusion

It is an interesting idea to basically make two meters in one, but the solution is definitely not perfect here, the meters are rather slow, both to use and when logging.
It has good selection of ranges and functions, but are missing a bit for a high-end meter (Like average and AC+DC), I am also missing the backlight.
The missing warning when a battery is low, together with a significant error in displayed values is problematic.
I like that the software has a math channel and it is possible to calculate some values, this can also be used when meter has done some stand-alone logging.
I will not say that this meter can replace two meters (Remember COM is shared), but for some application it is better than one meter.

Notes

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DMM Aneng AN860B+

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This is a cheap DMM with all common function.

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It included the DMM, a pair of probes and a manual (Where some specifications was missing).

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The probes has removable tip covers.

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The probes are rated for 10A, I would not trust that but use some more solid wire for 20A range.

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The thermocoupler is a cheap construction rated for max. 400° 0.75% ±2.5°±C

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When using the tilting bale the meter is nearly stable enough to turn the switch and push the buttons (If placed on a non-slip surface it will probably be stable enough).

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Meter without rubber sleeve, battery can be replaced without removing this sleeve.

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Display

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The above picture shows all the segments on the display.
Notice how u and m symbols are at multiple locations, making it possible to show them just before the unit.

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

Functions

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Buttons:

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.
Max/min: Starts recording maximum and minimum value, press to select between max/min.
Hz % (Blue): Shows frequency and duty cycle in AC ranges.
Select (Yellow): Select the ranges printed with yellow and between C°/F°
Hold: Freezes the display, hold down for backlight.

Rotary switch:

Off: Meter is turned off
VAC: Show AC voltage, using the blue button frequency and duty cycle can be selected.
VDC: Show DC voltage.
mV: Show DC or AC mV. In AC the blue button will show frequency and duty cycle.
ohm: Resistance, continuity, diode
Capacitance: Capacitor.
A: Current AC and DC. In AC the blue button will show frequency and duty cycle.
mA: Current AC and DC. In AC the blue button will show frequency and duty cycle. Watch out for burden voltage.
uA: Current AC and DC. In AC the blue button will show frequency and duty cycle.
°C/°F: Temperature.

Input

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20A: 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).
CON: The common terminal for all ranges.
xxx: All other ranges.

The terminals are a bit loose in the mounting due to the way they are made. My Keysight probes are very loose and cannot be fully pushed down (Standard banana plugs will fit). Opening up the meter and giving the terminals a squeeze may fix it.

Measurements

Volt and frequency
- At 10mVrms input frequency range is from 1Hz to 600kHz
- At 1Vrms input frequency range can be stretched to 8MHz
- Max/min needs about 340ms to capture a voltage.
- AC volt can measure up to about 2kHz (RMS will not work at the frequency).
- Frequency counter and duty cycle can only be selected in AC ranges.
- Input impedance is 11.5Mohm on DC and AC
- mV range is high impedance for DC and 10Mohm for AC
Current
- On the 6000uA & 600mA range there is an audible alarm when going above range.
- 20A range will give audible alarm at 10A after some time and immediately at 20A.
- Frequency counter and duty cycle can only be selected in AC ranges.
Ohm, Continuity, diode and capacity
- Ohm is 1V open and 0.39mA shorted
- Continuity is fast (About 20ms).
- Continuity beeps when resistance is below 50ohm.
- Continuity is 1V open and 0.39mA shorted
- Diode range uses 3.2V, max. display is 3V at 0.1mA, max. current is 1.7mA shorted
- 70000uF takes about 8 seconds to measure.
Miscellaneous
- There is no temperature compensation near the connector
- Current consumption of meter is 1.6mA (7.5mA with backlight)
- Meter works down to 2.2V where it turns off, battery symbol show at 2.4V.
- Reading will change slightly with battery voltage: 5 count on a 5V reading from 3V to 2.4V.
- Backlight 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, except from the top.
- Display updates around 3 times/sec
- Backlight will automatic turn off in about 15 seconds.
- Will automatic turn power off in about 15 minutes.
- Standard probes cannot be pushed fully down are very loose.
- Weight is 366g without accessories, but with rubber sleeve and batteries.
- Size is 180 × 89 × 44mm with rubber sleeve.
Probes
- Probe resistance 59mOhm for one.
- Probe wire is soft and 65cm long.

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A look at the capacity measurement waveform.

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Tear down

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Four screws and the back could be removed.

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6 more screws for the front.

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There is not much inside this meter. The main chip (IC2) is under the black blob, the calibration and function memory is a EEPROM (IC1:24C01). The buzzer (BZZP1) needs a transistor (Q2), same with the backlight (Q1).
There is a long voltage divider chain (R26, R27, R28, R29, R30, R35, R36) of 7 1.5Mohm resistors, this goes directly into the main chip. There is also the test current output (Used in ohm and capacity), this has a PTC (PTC1) and two transistors as clamp (Q3, Q4).
There is a 600mA glass fuse (F2) and two resistors for the uA (R23: 99ohm) and mA (R24: 1ohm) range and 5 diodes (D2, D3, D4, D5, D6) as protection. The 20A ranges has a 10A fuse (F1) and a wire resistor.
Notice the solder blop between tracks just above the battery terminal.

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This side of the circuit board only has the switches and the backlight. The display is connected with a zebra stip.

Conclusion

The meter is easily within the specified tolerances and it has lot of functions and ranges, but the CAT rating is fake.
Glass fuses cannot break high currents at high voltage, it requires ceramic fuses with sand inside. The protection on the ohm/capacity range do not look very robust, i.e. the meter may not survive high voltage on these ranges.
The 6000 count gives a good resolution at 4V and 5V, this can be useful.
Watch out for burden voltage in the 6mA and 600mA range, it can be significant.

I will call it acceptable DMM for hobby use (I am not happy about the bad fit of my other probes), but keep it away from anything with mains voltage and lots of amps.

Notes

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

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DMM UNI-T UT139C

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Uni-T has a large selection of DMM in their program, this model exist in A, B and C version, main difference is 2000, 4000 and 6000 count display, there is also a small variation of included functions. In this review I will look at the C version.

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The meter arrived in a red box with English and Chinese writing.

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The probes are branded UNI-T and rated for 10A and 1000V

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The removable tip must be on for best safety.

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The plug is fully shrouded.

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

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The tilting baile is just about stable enough to change range and use switches with one hand.

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The 600mA fuse is assible from the battery compartment.

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Display

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The above picture shows nearly all the segments on the display.

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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.

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) and max-min, 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, will select duty cycle in HZ range.
Hold/light (Yellow): Will freeze the display, hold down to turn on background light
Select/VFC(Blue): Selects the ranges printed with blue on the rotary switch, hold down to enable a low pass filter on AC volt.

Rotary switch:

Off: Meter is turned off
V: Show DC and AC voltage, use Select for AC and “Hz %” for frequency an duty cycle.
mV: Show DC and AC voltage, use Select for AC and “Hz %” for frequency an duty cycle.
ohm: Resistance, continuity, diode and capacitance.
Hz %: Frequency
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.
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Clik here to view.: External current clamp with 10mV/A

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).
CON: 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 do requires a zero crossing.
- Frequency input requires about 0.02Vrms before it works.
- Max/min needs about 350ms to capture a voltage.
- At 0.1Vrms input frequency range is from 0.9Hz to 4MHz
- At 1Vrms input frequency range is from 1Hz to 49MHz
- AC volt can measure up to about 2kHz, true RMS will not work at this frequency
- VFC only works in 600.0 and 600 volt mode and reduces bandwidth to about 800Hz
- Input impedance is 10-11Mohm on DC and AC
- Input impendance is high on mV DC range.
Current
- Frequency counter and duty cycle can only be selected in AC ranges.
- 10A range has audible alarm when current is 10A or above.
Ohm, Continuity, diode and capacity
- Ohm is 0.97V open and 0.30mA shorted
- Continuity is fast (About 20ms).
- Continuity beeps when resistance is below 50ohm
- Continuity is 1.01V open and 0.30mA shorted
- Diode range uses 3.2V, max. display is 3.000V at 0.09mA, max. current is 1.21mA shorted
- 70000uF takes about 10 seconds to measure.
Miscellaneous
- Current consumption of meter is 1.3mA to 1.7mA (6mA with backlight)
- Meter works down to 2.2V where meter turns off, battery symbol show at 2.4V.
- Backlight only works down to about 2.7V
- Reading is stable with varing battery voltage.
- The meter usual need a couple of display update to reach the final value.
- Viewing angle is good
- Display updates around 3 times/sec
- Backlight will automatic turn off in about 15 seconds.
- Will automatic turn power off in about 15 minutes.
- Standard probes fits fine, but cannot be seated fully.
- Generally precision is within a few counts, but there are ranges where it is 20 counts out.
- Weight is 354g without accessories, but with batteries and sleve.
- Size is 175 × 81 × 47mm with sleve.
Probes
- Probe resistanse 40mOhm for one
- Probe wire is soft and 88cm long.

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A look at the capacity measurement waveform.

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It is just outside tolerances on the high ohms measurements (2% out)

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 front required 4 screws for the terminals and 3 small screws for the circuit board.

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There is something under the display

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Two screws more to remove the display, but not the backlight, it is soldered to the circuit board.

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But I can bend it up (at least a few times).

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Here is the DMM chip (U1: DTM0660L) and the memory (U3: T24C02A) for calibration and functions setup. At the front is the NCV antenna and the indicator led (FG2). One of the voltage dividers are here (R1A, R1B, R1C, R1D: 4×2.5Mohm)

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Here is the range switch and some resistors.
A input chain (R2A, R2B, R2C: 3×300kohm), the uA shunt (R4: 99ohm) and the mA shunt (R5: 1ohm)

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On this side is the fuses, I wonder why the 600mA (F1) is longer than the 10A (F2). There is four MOV’s and two PTC for input protection. The transistors (Q2, Q3, Q8, Q9) do also look like protection. The 5 diodes (D1..D5) is protection for the uA and mA current range.

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Conclusion

This meter has all the usual functions and a few extra like NCV, VFC, external clamp (Any meter can use an external clamp, but this meter places the decimal point correct). As usual the burden voltage in the high mA is very bad.
The meter has a lot of protection and the fuses are rated for 600V, but I am lacking a current interrupt rating for the fuses.

This meter looks like it is fine for mains voltage and anything below.

Notes

UNI-T makes two versions of some meters, one living up to its CAT rating and one that do not.
UNI-T sell rebranded versions of their meters, i.e. you can get this meter with another name on it.

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DMM Aneng Mini 180

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This is a really cheap DMM with manual ranges and a minimum of functions, it is very small.

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There was no box included with the DMM.

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It included the DMM, a pair of probes and a instruction sheet.

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The standard probes are rather tiny.

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They use 4mm shrouded plugs, but they are very short (shroud about 10mm, normal is 20mm).

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The battery is a small 12V type (23A).

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The small probes looks large on this meter.

Display

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Typical display during usage, it will only show the number.
The HV symbol is only shown in the 500V ranges.

Functions

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Rotary switch:

Off: Meter is turned off
VAC: 500 & 200: AC voltage ranges.
hfe: NPN & PNP: Transistor tester
Battery test: 1.5V & 9V: They use the current input and shows current.
ADC: 200u, 2m, 20m, 200m: DC current range
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Ohm: 200, 2K, 20k, 200k, 2M
VDC: 200m, 2, 20, 200, 500: DC voltage range.

Input

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COM: The common terminal for all ranges.
Vohm: Voltage, resistance and Continuity input.
mA: Current and battery test input.

Measurements

Volt and frequency
- 5V AC volt readings drops 5% at about 10kHz, this do not include the 5 count error due to rectification.
- Input impedance is 1Mohm on DC
- Input impedance is 6Mohm on AC
- AC range uses a single diode, i.e. DC will show a (wrong) voltage if it has the correct polarity.
- Rated voltage 500V DC or peak AC on DC and 500V AC on AC.
Current
- uA and mA range is unfused (Back of meter says there is a fuse).
Ohm, continuity, diode and capacity
- Ohm needs about 1s to measure 100ohm (Manual range helps a lot).
- Ohm voltage is 0.3V open in 20k and above ranges and 25uA shorted in 20k range down to 0.3uA in 2M range
- Ohm voltage is 2.6V open in 2k and 200ohm ranges and 2.1mA shorted in 200ohm range and 1.2mA in 2k range
- Continuity is slow (About 500ms).
- Continuity beeps when resistance is below 56ohm.
- Continuity is 2.9V open and 1.4mA shorted
- Diode range is same as continuity and it will show ohm
- Rated overvoltage protection is 250V AC/DC for up to 10 seconds.
Miscellaneous
- 1.5V battery range uses a 37ohm resistor as load. Display shows current, not voltage, 40 is about 1.5V.
- 9V battery range uses a 360kohm resistor as load. Display shows current, not voltage, 25 is about 9V.
- Current consumption of meter is 0.58mA except 2k, 200ohm and Continuity where it is 3mA
- Meter displays values down to 2.8V where it turns off, battery symbol show at 6.6V.
- Readings will increase significantly in value below 6.2V (Shows about double voltage at 2.9V).
- Viewing angle is good
- Display updates around 2 times/sec
- Will not automatic turn power off
- Standard probes cannot be used, but banana plugs will work.
- Distance between terminals are non-standard.
- The meter usual need a couple of display update to reach the final value.
- Weight is 52.5g without accessories, but with batteries.
- Size is 100 × 51 × 23mm
Probes
- Probe resistance 80mOhm for one.
- Probe wire is fairly soft and thin, the are 60cm long.

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Tear down

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Two screws and the back could be removed.

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3 more and the circuit board could be removed.

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This side of the circuit board has the range switch, the LCD connection, the battery connections, the transistor tester socket and the input terminals.

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The electronic is on this side, near the current input terminals are the 3 current resistors: 1R00 (200mA), 9R00 (10mA) and 1000 (2000uA). A bit higher up on the circuit board are the two battery test resistors 360 (1.5V) and 361 (9V), they both include the 1ohm resistor in their final resistance.
The red wire and the trimpot do not look nice, the red wire is probably a last minute bug fix and the trimpot is because the correct part was not in stock.
I suspect that the M7 diode near the common terminal is for AC rectification.

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Conclusion

This is a simple and cheap DMM without any real input protection and with only a few ranges. This may be enough for some applications, but keep it away from mains voltage.

The battery test is not very useful with display of current, i.e. is 23 a good or bad battery?

Notes

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

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Here is an overview and comparison of my three DMMs.

Left to right they are a Beckman Tech 310, Digimess DM200 and BSide ZT102.
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I recently purchased a 2.5000V .01% reference from Doug Malone. I will use that to compare DC accuracy at a single point. Best I can do with my home gear.

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Beckman Tech 310

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Beckman Instruments, now Beckman Coulter, is an American manufacturer of Biomedical Instrumentation. In the early 1980s Beckman made a series of high quality hand held DMMs. A few years later San Diego based Wavetek took over Beckman’s DMM line and it disappeared. I bought mine around 1982. At the time analog meters were still common.

This manual ranging meter is easy to use. The large selector knob has positive detents and a quality feel. Measurements are quick, perhaps because the meter isn’t auto ranging and is 1999 count.

The meter is exceptionally durable. It survived significant voltage on the resistance settings. I’ve dropped it many times and it keeps on working. I still use it regularly. Even the original test leads are still good.

I’ve never had the meter calibrated. After 35 years it is still in spec and only 1 count off!

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Single Ceramic fuse accessible from the battery compartment. The Tech 310 pre-dates Cat I, II, III, and IV ratings. I dunno. It is pretty well made and held up fine measuring high voltages. I’ve used the 1500VDC and 1000VAC scales before. I’m not sure if I would risk it now. Any capacitors in the meter are getting really old.

Removing the back cover reveals a large shield.

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There are two circuit boards full of 1980’s tech. Note the single potentiometer just to the left of the top board. That sets DC calibration. By some amazing coincidence 2.50V is the set point Image may be NSFW.
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After a slight adjustment.

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DMM 5 in 1 (VA19)

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This is a fairly cheap DMM with all common function and some environment measurements also.
The one I got do not have a brand name on it.

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

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The ony rating on the probe is 10A. The isolated tip is nice.

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The termocoupler looks fairly standard

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When using the tilting bale the meter is not stable enough to turn the switch and push the buttons.

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On the top of the meter is the microphone, photo sensor and humidity sensor. Due to the construction of the meter it is not possible to alight the light sensor directly vertical or horizontal except on eyesight.

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Space is very tight in the battery compartment, this is not very nice.

Display

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The above picture shows all voltmeter the segments on the display, segments for enviroment is not shown.

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Here is one of the symbols missing above (x10 Lux).

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

Functions

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Buttons:

HOLD: Freezes the display, press again to unfreeze.
LIGHT: Turn on the background light, cannot be turned off manually.
FUNC.: Select between AC/DC and ohm/continuity/diode/capacitance
RANGE: Manual range in V, ohm and mA
Hz/DUTY: Select Hz and duty cycle in volt and current ranges. Select duty cycle in frequency range.
REL: Zeros display and shows relative values in all ranges.

Rotary switch:

Off: Meter is turned off
V: Used for mVDC, VDC and VAC, use FUNC. to select between AC/DC
Ohm: Used for ohm/continuity/diode/capacitance, use FUNC. to select with.
Hz: Frequency, use HZ/DUTY button to select between frequency and duty cycle.
1°C: Temperature
0.1°C: Temperature
%RH: Humidity
dB: Sound level.
Lux: Light
x10Lux: Light, there is no comma or K on display, but a X10 LUX annotation in the display.
400mA: Current AC and DC. Starts in DC, press FUNC for AC. Use HZ/DUTY to show frequency.
10A: Current AC and DC. Starts in DC, press FUNC for AC. Use HZ/DUTY to show frequency.

Input

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10A: High current, only rated for 10A in 15 seconds
mA: The lower current ranges and the thermocoupler input.
COM: The common terminal for all ranges.
xxx: All other ranges.

The terminals are a bit loose in the mounting due to the way they are made. Standard probes will fit.

Measurements
Spaceing between input terminals is not standard!

Volt and frequency
- Frequency input needs 180mV rms before it will count.
- At 1Vrms input frequency range is from 2Hz to 8MHz
- AC volt can measure up to about 1kHz
- Frequency counter and duty cycle do not require zero crossing in Hz range, but do in V range.
- Input impedance is 10 to 11Mohm in DC and AC
- Rated overload protection on mV range is 250V DC/AC
- Rated overload protection on V range is 600V AC/DC
- Rated overload protection on frequency range is 250V AC/DC
Current
- On the 400mA and 10A range there is an audible alarm when going above range.
- 10A range is unfused!
- 400mA and temperature range is protection is 500mA/600V 5×20mm fuse.
Ohm, Continuity, diode and capacity
- Ohm needs about 4s to measure 100ohm
- Ohm is 0.42V open and 0.21mA shorted
- Continuity is slow (About 120ms).
- Continuity beeps fully when resistance is below 28ohm and stops making noise at about 60ohm.
- Continuity is 0.44V open and 0.21mA shorted
- Diode range uses 1.5V, max. display is 1V at 0.2mA, max. current is 0.56mA shorted
- 100uF takes about 20 seconds to measure.
- The lowest capacity range is not very precise
- Rated overload protection is 250V DC/AC
Miscellaneous
- Sound meter do not follow a A or C curve and will show too high at lower frequencies (+10dB at 250Hz from A)
- Light meter is fairly precise with incandescent, but is filtered very badly.
- Due to the angled top it is difficult to hold the light sensor perpendicular to the light source.
- Thermocoupler input is not very precise at higher and very low temperatures.
- Current consumption of meter is 2.0mA (40mA with backlight)
- Current consumption of meter in enviroment is 7mA (45mA with backlight)
- Display fades at 1.9V, battery symbol show at 6.8V (Second symbol at 2.3V).
- Voltage reading is stable down to about 2.4V battery voltage
- Temperature reading are stable down to about 4.7V battery voltage
- Backlight 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
- Standard probes fits, but distance between input terminals is non-standard.
- Backlight fades in about about 10-12 seconds.
- Will automatic turn power off in about 15 minutes.
- Weight is 290g without accessories, but with battery.
- Size is 180 × 84 × 48mm.
Probes
- Probe resistanse 36mOhm for one.
- Probe wire is soft and 82cm long.
- Aligator clip resistanse 11mOhm for one.
- Aligator clip wire is soft and 5cm long.

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A look at the capacity measurement waveform.

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The capacity in about 4% wrong in 1nF range.
Lux range is 4000 and 40000lux

Tear down

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Four screws and the back could be removed.

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6 more screws for the front.

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And four more screws to remove the circuit board.

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Not much on this side, the green resistor is the 400mA shunt. The wire below the two red terminals is the missing 10A fuse.

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There is lot of chips on this side and also a lot of trimmers (I counted 12), I tried to identify some of the chips:
IC3: 27L2C – TLC27L2 Dual precision OpAmp
IC7, IC8, IC9, IC10, IC11: GZ525 (ST) – probably a dual OpAmp
IC5: 271C – (TI) TLC271C Programable OpAmp
IC6: LM358 (TI) – Dual OpAmp
IC2, IC12: 7530-1 – Voltage regulator
Generally there is not much protection, near the voltage input is a green PTC

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At the front/top is the sensors. A humidity sensor (White ceramic), a photo diode on its own circuit board and a microphone.

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Conclusion

Without a fuse on the 10A range the meter can not live up to any CAT rating.
I have not done a fast check of the environment functions and they did not look very precise. The normal DMM functions works fine, but it is missing uA and have a fairly high burden voltage in the 400mA range.
For comparing light sources with the same type of bulb the light meter is fine, but it cannot compare a led to a incandescent correctly, with sound it can compare noise from the same source, but because its sensitivity do no match the ear, it cannot be used to evaluate noise levels.

Notes

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DMM Amprobe AM-570

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This is the top meter in the Amprobe 5xx series, it is well packed with functions and has fairly good specifications.

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The meter is packed in a clamshell box, on the front it has some highlights for this meter and on the back it compares the different models in the 5xx series.
The 540 and 550 is missing, they are basically the same as 560 and 570, but with different safety ratings and only sold in EU.

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It included the DMM, a pouch, a pair of probes, two thermocouples and a dual thermocoupler adapter, a safety information sheet and a mini CD with the manual (It can also be downloaded).

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I forgot this strap in the above picture. It can be used to hang the meter from all types of hooks.

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Everything could fit in the supplied pouch.

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The two thermocouplers are standard K type with a standard K type plug.

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The thermocoupler adapter takes two standard thermocouplers and connect them to 3 terminals on the meter. T1 is volt input and common, T2 is mAuA input and common, in both cases common is the negative terminal.
This also means it is possible to use one thermocoupler with banana plugs as either T1 or T2.

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Probes are branded with Amprobe and has removeable tip covers.

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The plug is fully shrouded and standard probe plug size.

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The meter has a led at the front for flashlight usage, it is behind a plastic window.

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The tilting bale works very well, it is easy to extended and the rubber feet secures the meter do not slide around when pushing buttons or turning the range switch.

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Display

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The above picture shows all the segments on the display.

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Typical display during usage, it will show the main number and what measurement is selected. In addition to this a secondary readout with frequency will be shows in AC modes, with max or min in max/min mode and with base value for REL modes. It is not used for dual thermocouplers.

NCV do not have its down display, it shows OL on the display and only indication of mains is the buzzer.

Functions

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Buttons:

Range: Will disable auto range and change range, hold down to activate auto range. This will also select between the two thermocouplers.
Rel: Shows values relative to current value (The base value will be shown in the dual display), will also select manual range. Press again to disable. Hold down to turn flashlight on.
Max/min: Select max/min mode, press to toggle between max and min in secondary readout, hold down to disable again. Holding the button down will enable peak detect, i.e. a very fast max/min mode.
Hold: Freezes the display, hold down for backlight.
Select (Yellow): Select the ranges printed with yellow
400kohm: Hold down for loading input terminals, the beeper will sound while this button is activated and display will show Low-Z.

Rotary switch:

Off: Meter is turned off
VAC: Show AC voltage, use yellow button to activate a low pass filter.
VDC: Show DC voltage, use yellow button for non-contact voltage mode.
mV: Millivolt DC, use yellow button for frequency and duty cycle.
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°C°F: Temperature, use yellow button for C/F and range to select between T1, T2 and T1-T2
uA: Microampere current, use yellow button to select AC
mA: Milliampere current, use yellow button to select AC, the burden voltage is very bad in the high mA range.
A: Ampere current, use yellow button to select AC
Off: Meter is turned off

Input

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A: High current, maximum current is 10A
mAuA: The lower current ranges, this is also input for T2 temperature sensor.
CON: The common terminal for all ranges.
xxx: All other ranges.

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The thermocoupler adapter with two thermocouplers.

Measurements

Volt and frequency
- Frequency counter is always displayed in AC ranges
- Frequency input can handle a DC offset of about ±3.5 volt, but requires a few seconds to compensate for it.
- Frequency input requires about 0.2Vrms before it works.
- At 1Vrms input frequency range is from 4Hz to 50MHz
- At 2Vrms input frequency range is from 4Hz to 60MHz
- Duty cycle works from 0.2% to above 99% at 100kHz with 10Vpp, precision is within 0.4.
- Duty cycle works from 10% to above 90% at 10kHz with 1Vpp, precision is within 4 most of the time.
- 1 VAC is 5% down at 3kHz (RMS will not work at the frequency).
- 1 VAC with LPF is 5% down at 570Hz (RMS will not work at the frequency).
- Peak needs about 1.5ms to capture a voltage and works for both AC and DC.
- Max/min needs about 120ms to capture a voltage.
- If there is a large DC voltage with AC selected, it will show 0 (or a low value).
- Input impedance is 10-11Mohm on DC and AC
- The mV range is only for DC and is 3-10Mohm below 3.5 volt, above it drops to a few kohm
- Pressing the 400kohm button will put 390kOhm across the voltage input in all ranges.
- Bargraph is faster than number display (Rated 20 times/sec).
- Rated overload protection is 1000VDC on DC range and 1000VAC on AC range
- Frequency input resistance is above 1Mohm below 4 volt, but then drops to 3kOhm
Current
- Frequency counter is always displayed in AC ranges
- uAmA fuse is 0.5A/1000V 6.3×32mm
- A fuse is 15A/1000V 10×38mm
- There is an audible alarm when current is above 10A.
- Burden voltage is very bad at high mA, it is 2.1V at 590mA (Use 10A range to avoid this).
- There is an audible warning and blinking warning text when using non current ranges with a probe in mAuA or A input.
Ohm, continuity, diode and capacity
- Ohm needs about 3.2s to measure 100ohm
- Ohm is -1.2V open and -0.85mA shorted
- Continuity is very fast (About 4ms).
- Continuity beeps when resistance is below 10ohm and stays on til 50ohm
- Continuity is -3.3V open and -0.85mA shorted
- Diode range uses 3.1V, max. display is 2.900V at 0.07mA, max. current is 1mA shorted
- 600uF takes about 6 seconds to measure.
- Rated overload protection is 1000V peak
Miscellaneous
- When temperature probe is outside range it will be reported as “open”
- Current consumption of meter is 7.5mA and 2mA extra for AC (24mA with backlight in DC, 21mA with flashlight in DC, in AC with backlight+flashlight it is 39mA)
- Meter works down to 3.4V where display starts to fade and is invisible at 2.1V, battery symbol show at 7V.
- A 5V reading will change 2 count from 9V to 2.1V
- Backlight and flashlight start to fade at 3.6V
- The meter is fast to show correct reading.
- Viewing angle is good
- Display updates around 3 times/sec
- Backlight and flashlight will turn off with the automatic power off, not before.
- Will automatic turn power off in about 15 minutes.
- Banana plugs and standard probes is difficult to fully insert on the mAuA and A ranges, but works fine on V input.
- The meter has a warning beep for wrongly inserted probes in the two ampere terminals.
- Generally the precision is nearly “spot on”, i.e. usual only a few counts out.
- Weight is 370g without accessories, but with batteries.
- Size is 189 × 89 × 50mm.
Probes
- Probe resistance 24mOhm 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 resistance.

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Actual burden voltage at 6mA is 0.96 volt an internal diode bridge reduces the burden voltage at higher currents.
Actual burden voltage at 600mA is 2.05 volt an internal diode bridge reduces the burden voltage at higher currents.
With high DC voltage present the AC range will not show low AC voltages.
NCV only use buzzer as indication, not light or display.

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 is shaped to follow the shape of the box. In addition to the screws there are two clips at to keep the circuit board in place.

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Four screws and I could take the circuit board out, the input terminals was rather difficult to get out.
Only the two screws was necessary, the two at the top was only for the display cover.

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There is some shielding in the plastic for the ampere input. It matches slots in the circuit board.

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There is some electronic below the display.

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There protection for R80 in the current shunt (D10, D11, D15, D16) is on this side. The 10A sense line has a series resistor (R25 5Mohm). The 400kohm switch is 4 switches and two resistors (R53, R54, 2×200K) in series.
There is two leds for background light to the LCD display.
The big chips is a microprocessor (MSP430F5310 with 32K program memory and 6K ram) and there is a EEPROM (IC5: ATMLH838).

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There is a lot of input protection on this meter. Two sets of double PTC’s (PTC1, PTC2, PTC3, PTC5) followed by dual MOV’s (SG1, SG1, SG3, SG4) and then lots of transistors pairs, some of them with fairly large transistors (Q7, Q8 & Q9, Q10 & Q11, Q12 & Q13, Q14 & Q16, Q17). The MOV (SG5) besides the 0.5A fuse is probable protection for T2 input). The 10Mohm input is made from four resistors (R1, R2, R3, R4: 4×2.5Mohm).
The full current shunt protection (D3, D4, D5, D6, D9) is missing
The actual current shunt is a bit special, it uses a couple of resistors in series and parallel (R33, R34: 2×1ohm in parallel, R80, R32, R81: 4.5ohm, 45ohm, 450ohm in series). This makes the mA current shunt 0.5ohm + 4.5ohm with diodes and explains the very bad burden voltage. In the uA shunt the diodes clamps the 450ohm resistor.
The two large chips are a DMM frontend (IC2: ES51995A: 6000 count) and a LCD driver (IC1: BU9799KV). The frontend has an external True RMS converter (IC6: ES636: 200 segment driver). There is also a charge pump (IC4: CAT550) making a negative voltage from the internal 3.5V that is made with a linear regulator (Q1).
At the top of the circuit board is the NCV antenna

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Conclusion

This is a fairly advanced meter with many functions and most of the working perfectly, but I do not like the uA and mA ranges, the burden voltage is way to high and I do not have confidence in the protection, because the diodes are missing (This circuit is from the DMM chip datasheet, there is also a circuit that requires an OpAmp and gives low burden voltage), the meter is also missing the low A range. The NCV is audio only, this is not a good solution.
Except for the above the meter is fairly good with lots of extra functions like: flashlight, Peak, LPF, dual temperature inputs, Low-Z.

Notes

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DMM Aneng AN8002

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This is a cheap DMM with all common function.

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There was no box included with the DMM, only a plastic bag with everything inside.

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

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The standard probes has removable tip covers.

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The plug is fully shrouded.

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The thermocoupler is the usual cheap type.

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The body of the DMM feels solid, the plastic is rather smooth, i.e. the DMM can easily slide on a surface. The tilting bale is a bit flimsy and do not give enough support for pressing buttons and turning the range switch.

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Display

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The above picture shows all the segments on the display.

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

Functions

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Buttons:

Hold (Blue): Will freeze display, press again to unfreeze, hold down to activate background light.
Sel (Yellow): Select the ranges printed with yellow.

Rotary switch:

Off: Meter is turned off
V % Hz: Show voltage, using the yellow button will cycle between VDC, VAC, freq. and duty cycle.
mV: Show millivolt, using the yellow button will cycle between VDC and VAC
ohm: Resistance, continuity, diode and capacitance, use yellow button to select.
Hz: Frequency and duty cycle, this is fairly low input impedance above 2V
A mA: Current AC and DC.
°C °F: Temperature, will show DMM temperature when no probe is mounted.

Input

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A: The two A ranges.
COM: The common terminal for all ranges.
xxx: All other ranges, including mA. It is always problematic when a current range shares connector with a voltage range, if the switch is in the wrong position the (hard to replace) fuse will blow (at least). This will only affect current, voltage will still work.

Measurements

Volt and frequency
- 1 VAC is 5% down at 2.1kHz (RMS will not work at the frequency).
- Input impedance is 10-11Mohm on DC and AC
- mV range is high input impedance for DC and 10Mohm for AC below 1.5V, above they wil soon drop to 2kohm
- At 100mVrms input the frequency counter works from 1Hz to 4MHz
- 1Vrms input will extend the frequency range to 7MHz
- Frequency counter and duty cycle need a zero crossing in both Hz and AC range.
- Duty cycle works from 2% to above 99% at 100kHz with 1Vpp, precision is within 0.5.
- V input works with a blown mA fuse.
- Frequency input is 10Mohm below 1.5V and drops to 2kohm at about 3V
Current
- 10A range is badly calibrated at high current.
- 10A range will change some percent at 5-10A current due to heating.
- 10A range will give an audible alarm when current is above 10A
- 600mA range will give an audible alarm when current is above 600mA
- mA range is protected with 0.6A/250V 3.6×10mm fuse
- 10A range is protected with 10A/250V 3.6×10mm fuse
Ohm, continuity, diode and capacity
- Ohm needs about 2.7s to measure 100ohm
- Ohm voltage is 1V open and 0.40mA shorted
- Continuity is fast (About 10ms).
- Continuity beeps when resistance is below 50ohm.
- Continuity is 1V open and 0.40mA shorted
- Diode voltage is 3.2V with display of up to 3.000V with 0.2mA, maximum current is 1.8mA shorted
- 70000uF takes about 10 seconds to measure.
- No protection level is specified, only that not voltage must be present.
Miscellaneous
- Current consumption of meter is 1.6mA (7mA with backlight)
- Meter works down to 2.2V where it turns off, battery symbol show at 2.4V.
- Readings are stable with changing battery voltage.
- Backlight only works down to about 2.6V where it is fairly dim.
- Viewing angle is good.
- Display updates around 3 times/sec
- A beeper will sound shortly before the meter turns itself off
- Backlight will automatic turn off in about 15 seconds.
- Will automatic turn power off in about 15 minutes.
- The meter usual need a couple of display update to reach the final value.
- Standard probes fits fine, but cannot be seated fully.
- Weight is 135g without accessories, but with batteries.
- Size is 130.2 × 65 × 32.3mm
Probes
- Probe resistance 55mOhm for one.
- Probe wire is fairly soft and 65cm long.

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A look at the capacity measurement waveform.

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Frequency input resistance. mV looks similar, except DC is high impedance at low voltage.

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Tear down

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Four screws and the back could be removed.

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Three more for the circuit board and two for the display.

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On this side there is only the switches and the connection to the display. The 10A current shunt is missing a solder joint on this side.

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The two small fuses are not designed for high CAT ratings.
R24 is a 1ohm resistor for mA current range and R23 is a 99ohm resistor for the missing uA range. R29 and R30 is the 10Mohm input divider.
D5 is a bidirectional zener diode to protect the mA current shunt.
Q3 & Q4 is input protection together with PTC1. The DMM chip is under the black blob and the IC1 (24C02) beside it is a EEPROM to store functions and calibration in.

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Conclusion

The meter is easily within the specified tolerances (Except 10A) and it has lot of functions and ranges, but the CAT rating is fake.

This is a small DMM in size, but has most of the expected functions in a universal DMM. It is missing the uA current range,

I do not like the small fuse size, they cannot break high voltage or high current and they can be hard to source. The current range on the voltage input is also a bad idea.

I will call it good DMM for hobby use, but keep it away from anything with mains voltage and lots of amps.

Notes

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

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DMM Uyigao UA18

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This is a small pocket DMM with voltage, ohms and capacity, but without current.

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The meter was in a clamshell pack. On the back is a comparison between the two meters in the series

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In the box was the meter and a manual in English.

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The probes and wires need some pressure to close the cover.

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The probes are small and without any markings.

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The probes are directly connected to the meter, no plugs and sockets.

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The range switch is a bit tight, but the way it is made gives a good grip and it is easy to turn without the meter moving around.

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Display

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The above picture shows all the segments on the display. Not all are used by the meter.

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Typical display during usage, it will show the selected range and value.

Functions

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Buttons:

Select: Select between ohm, diode, continuity and capacitance
Relative: Store current display value and show all new values relative to this value.
Hold: Will freeze the display reading, until pressed again.
Hz/duty: Will select between voltage, frequency and duty cycle.

Selection of Relative and Hz/duty will disable auto ranging and it stays disabled
The Select and Hz could have combined, they are not used in the same ranges.

Rotary switch:

Off: Meter is turned off
VDC: DC voltage and frequency/duty cycle.
VAC: AC voltage and frequency/duty cycle.
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Input

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

Measurements

Volt and frequency
- At 1V rms input on DCV/ACV the frequency counter range is from 1Hz to 29kHz
- At 2V rms input on DCV/ACV the frequency counter range is from 1Hz to 44kHz (ACV was 51kHz)
- Duty cycle works from 2% to 98% at 1kHz with 4Vpp, precision is within 1.1 (Mostly 0.3)
- Both DC and AC frequency counter inputs need a zero crossing.
- 1V AC readings is 5% down at 2.7kHz
- Input impedance is 10-11Mohm, this includes the frequency selection.
- Input protection is 500V AC/DC.
Current
- There is no current ranges
Ohm, continuity, diode and capacity
- Ohm needs about 3.7s to measure 100ohm
- Ohm is 0.43V open and 0.19mA shorted
- Continuity is moderate (100ms) (It is faster, but then it will miss sometimes).
- Continuity beeps when resistance is below 70ohm
- Continuity is 0.44V open and 0.19mA shorted
- Diode range uses 1.5V, max. display is 0.999V at 0.17mA, max. current is 0.56mA shorted
- 90uF takes about 16 seconds to measure.
- Capacity range is not reliable at high values, with a 100uF capacitor is showed values from nF up to the correct 100uF.
- Rated overload protection is 250VDC/VAC
Miscellaneous
- Current consumption of meter is 0.8mA, except in AC where it is 1.3mA.
- Meter fails below 1.6V, battery symbol show at 2.4V.
- Readings will drift about 5 count when from when battery symbols shows to the meter fails.
- Viewing angle is good
- Display updates around 3 times/sec
- Will automatic turn power off after about 33 minutes
- The meter often need many display update to reach the final value.
- Weight is 95g without accessories, but with sleeve and batteries.
- Size is 107 × 56 × 13mm (probes not included) and 120 × 80 × 16 in sleeve.
Probes
- Probe wire is a bit thin, the are 44cm long.

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Frequency input resistance in voltage DC position.

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Frequency input resistance in voltage AC position.

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The specifications list a 400.0mV DC range and a 4.000nF range, they were not present on the meter.
The lowest capacity range (51nF) has a offset up to 0.4nF, this give a large error on low nF capacitors
The meter cannot measure DC when there is a large AC voltage.

Tear down

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I had to remove one screws, to open it, this is also required when replacing battery.

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There are a few details to make the meter as flat as possible (Like parts placed outside the circuit board or in cut-outs in the board).

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The round features are probably designed to put some pressure on the circuit board to make the meter more stiff.

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6 screws and a locking ring must be removed to get the circuit board out.

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The battery is mounted in a cut-out. The battery holder is not a standard holder, but some metal parts soldered to the circuit board

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it looks like 3 connections to the plus wire: A voltage divider (R3-1, R3-2, R3-3, R4-1, R4-2: 5×2Mohm) for the voltage ranges. A sense input for the ohm/capacity range (R26, R27: 412kOhm+487kOhm) and a current output with a PTC. There is a single transistor clamp (T1) on the PTC.
There are 3 trimpots for calibration of the meter.
The buzzer has an inductor (L1) to boost the voltage, and there is some holes in the circuit board for the sound.

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Conclusion

The meter says CAT II, but there is no voltage, i.e. not a valid CAT rating.
The meter do not have current ranges and is missing some ranges compared to the specifications, but for a pocket meter there is a fair amount of ranges and functions. The meter is often very slow on reaching the final value.
It is a fairly decent meter for it size, but be aware of its limitations.

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DMM Handskit 117C

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I bought this meter as “HY-19” without any brand on Aliexpress, but when I received it the name had changed to the above.

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This meter did not come in a cardboard box, but in a plastic box with lot of accessories included.

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There was the meter, instruction sheet and probes, but in addition there was extra sharp and thin probe tips, alligator clips, hooks and a SMD tweezers.

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The probes are rated for 1000V and 20A in CAT II environment.

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They include a tip protection.

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The plug is fully shrouded with the short type of shroud (17mm).

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This probe can be used when measuring on small stuff or be stuffed into some connectors to measure while it is connected.

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The tilting bale is just about stable enough to change range and use switches with one hand.

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Display

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

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Typical display during usage, it will show the number and what measurement is selected.
AUTO is for auto range and APO is for automatic power off.

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The electric field detection (NCV) shows from 1 to 4 bar depending on field strength. It is very sensitive.

Functions

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This meter will remember what was selected with SELECT and start in the same function next time, power off will not reset this.

Buttons:

Hold: Will freeze the display, hold down to turn backlight on.
Range: Switch to manual ranging and will also change range, hold down to get back to automatic.
Rel: Remember the current reading and shows all further values relative to this, will disable auto ranging.
Hz %: Select Hz and duty cycle display in AC ranges, is also used in Hz range to select duty cycle.
Select (Orange): Selects orange marked ranges for each position on the range switch.
Max/min: Starts capturing maximum and minimum values, pressing it will change between max/min on the display, holding it down will return to normal. This function will disable auto ranging.

Rotary switch:

Off: Meter is turned off
VAC: Show AC voltage, use Hz to display frequency.
VDC: Show DC voltages.
mV: Show millivolt, use SELECT to change between DC and AC. In AC Hz can be used to show frequency.
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Clik here to view.: Resistance, continuity, diode and capacitance, use SELECT to change between them.
Hz: Frequency and duty cycle, this only works in AC ranges and on the Hz setting.
A: Current DC and AC, use SELECT for AC and “Hz” for frequency and duty cycle.
mA: Current DC and AC, use SELECT for AC and “Hz” for frequency and duty cycle.
uA: Current DC and AC, use SELECT for AC and “Hz” for frequency and duty cycle.
NCV: Non contact voltage or electric field detection.

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.
COM: The common terminal for all ranges.
xxx: All other ranges.

Measurements

Volt and frequency
- Frequency input requires a zero crossing.
- Max/min needs about 390ms to capture a voltage.
- At 0.1Vrms input frequency range is from 0.8Hz to 4.5MHz
- At 1Vrms input frequency range is from 0.9Hz to 7.8MHz (At 3.5V rms I reached 70MHz).
- Duty cycle works from 2% to above 94% at 100kHz with 1Vpp, precision is within 0.3
- 1 VAC is 5% down at 2kHz
- Input impedance is 10-11Mohm on DC and AC.
- Millivolt range has high input impedance in DC up to 2V, then it drops to 2Kohm, AC mV is 10Mohm, but drops to 2kohm
- Frequency input is 1-3Mohm up to 2V, then it drops to 2kOhm
- Voltage ranges rated to 1000VDC or 750VAC
- mV range rated to 550V
- NCV is very sensitive.
Current
- mAuA is protected with 0.6A/250V 6.3×32mm fuse (More correctly 5.9×30mm it is not sand filled, i.e. not a HRC fuse)
- A is protected with 10A/250V 10×38mm fuse
- There is audible alarm when current goes about 6.2mA in uA range.
- There is no audible alarm in mA range.
- There is audible alarm when current goes above 10A in 10A range.
Ohm, Continuity, diode and capacity
- Ohm needs about 2.5s to measure 100ohm.
- Ohm is 0.97V open and 0.39mA shorted
- Continuity is very fast (Below 10ms).
- Continuity beeps when resistance is below 50ohm
- Continuity is 1.01V open and 0.39mA shorted
- Diode range uses 3.2V, max. display is 3.000V at 0.16mA, max. current is 1.7mA shorted
- 70000uF takes about 8 seconds to measure.
- Ranges rated to 550V ACpeak/DC for 10 seconds.
Miscellaneous
- Current consumption of meter is about 2mA, except ohm where it is 4.3mA (12mA with backlight in volt)
- Meter works down to 1.8V where meter turns off, battery symbol show at 5.8V.
- Backlight fades with falling voltage it is about gone at 2.6V
- Reading is stable until about 2.0V where it increase a few count.
- The meter needs a couple of display update to reach the final value.
- Viewing angle is good
- Display updates around 3 times/sec
- Backlight will automatic turn off in about 15 seconds.
- Will automatic turn power off in about 15 minutes.
- Standard probes cannot be fully inserted.
- Weight is 366g without accessories, but with batteries and sleeve.
- Size is 183 × 90 × 46mm with sleeve.
Probes
- Probe resistance 36mOhm for one
- Probe wire is soft and 88cm long.
- Gripper wire resistance is 10mOhm
- Griper wire is 57cm long.
- SMD tweezers wire is 51cm long.

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A look at the capacity measurement waveform.

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Frequency input resistance.

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The low capacity range has bad tolerances, but that range is not covered in the specifications. The highest ohm range is about 2% out around 50Mohm, but within tolerances at lower values.

Tear down

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I had to remove 4 screws to open it.

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The meter uses ceramic fuses and fairly large ones.

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The large fuse is rated for 100kA, this is probably a bit optimistic. The small fuse is without any printing on it.

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I needed to remove 6 more screws to get the circuit board out.

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On this side there is no components, but only areas for the different switches and a NCV antenna at the top.
The lcd required two screws more and unsoldering the backlight. It did not look like there was anything under it, so I let it stay on this time.

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The inside looks fairly standard for a cheap multimeter. Besides the large fuse is the mA (R52 0.99ohm) and uA (R37: 99ohm) shunts, they are protected by a couple of diodes (D8..D12). Above the small fuse is the input divider (R44..R47: 4×2.5Mohm). Output protection for ohms is PTC1 and two transistors (Q3 & Q4), this protection circuit is also used for mV and Hz input.
The 9V battery goes to a voltage regulator (IC6) and is then used to supply the multimeter IC and the EEPROM (24C08N).
This side do also have a NCV antenna at the top of the circuit board.

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Conclusion

As usual the CAT rating is fairly optimistic with fuse specifications saying 250V.
This meter has all the usual ranges, except temperature, the only “extra” function is NCV. With all the included accessories this is a nice meter kit for low voltage and mains in the home.

Notes

This meter is a rebrand from HY-19 (That is probably also a rebrand).

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DMM Vici VC8145

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This is a fairly cheap bench DMM from a Chinese manufacturer.

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No nice box for the meter was included, probably to save shipping cost (I bought in on Aliexpress).

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It included the DMM, a pair of probes, short leads with alligator clips, a thermocoupler, a usb cable, a mains cable with plug converter, a manual, a screwdriver and a CD.

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The probe is marked CAT III 1000V, but do not have tip covers, i.e. the marking is not correct. The meter is only for CAT II and do not need CAT III probes.

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The plug is fully shrouded with short shroud.

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The thermocoupler is a standard cheap one.

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The short leads with alligator clips is nice for component testing.

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RS232 serial cable, do anybody use these cables anymore?

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This meter uses buttons to select function, but it only have the regular 4 input sockets (Some bench meters have 6).

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The mA fuse is hidden behind the mA socket. It do not follow with the removeable part out.

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The meter has a build in stand that can tilt it a bit.

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On the back is mains connection with voltage adjustment and RS232 connection.

Display

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The above picture shows all the segments on the display.

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

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In temperature mode it will show temperature in Celsius and Fahrenheit

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The dual display can show many different values in the different volt ranges. I have listed them below:

REL will use the second display to show the reference and disable the other dual display functions.
Max/min/Avg will use the the second display to show the value and disable the other dual display functions.
Dual displays in VDC: AC+DC/Hz, AC+DC/VAC, dBm/VDC, dBm/VAC, dBm/Hz, dBm/AC+DC
Dual displays in VAC: VAC/Hz, VAC/msLow, VAC/msHigh, VAC/%Low, VAC/%High, dBm/Hz, dBm/VAC
Dual displays in mV: VAC/Hz, VAC/%High, VAC/%Low, VAC/%Low, VAC/%High, dBm/Hz, dBm/VAC, dBm/VDC, dBm/AC+DC
Dual displays in mA & A: AC+DC/IAC, IAC/Hz
Dual displays in frequency: Hz/%High, Hz/%Low, Hz/msHigh, Hz/msLow
Dual displays in Temp mode is temperature in Celsius and Fahrenheit

Functions

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Mode buttons:

VDC: Select VDC mode, it is also used for AC+DC and dBm
mV: Select mV mode for AC and DC, it is also used for puls width and dBm.
Ohm: Select ohm mode, a special high ohm mode can be selected.
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Clik here to view.: Select capacitance mode.
VAC: Select VAC mode, it is also used for puls width and dBm.
mA: Select mA mode for AC and DC, it can also show AC+DC and frequency
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Clik here to view.: Select diode and continuity mode, it is the same mode and will always show voltage.
Hz/Duty: Select logical frequency mode, this will show duty cycle in secondary display.
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Clik here to view.: Turn background light on, this makes the display easier to read.
20A: Select ampere range, it can also show AC+DC and frequency
Temp: Select temperature mode, default is internal temperature, press SELECT to use a thermocoupler.
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Clik here to view.: Select square wave output.

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Function buttons:

Set: Used for setting limits and timer values.
Max/min: Select max/min/max-min/average, hold down to turn off. The value is showed in the secondary display.
Range: Manual range, hold down to return to auto range. Also used for impedance in dBm mode.
Rel: Store a reference (Shown in secondary display) and show values relative to this. Press again to store a new reference, hold down to cancel.
Timer: Can specify an end time to a max/min measurement (Only an alarm, will not stop the measurement).
Hold: Auto hold function, when input is stable the display will update and the buzzer will signal. Press again for Peak hold. Hold down to disable.
2nd view: Select value in secondary display. This only works when secondary display is on!
Select: Select function, this is AC/DC and secondary display on (Use 2nd view to change secondary display function).
Power: Physically turn the power on/off to the meter.

Input

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20A: High current, it can only withstand 20+ ampere for a short time (Fuse is 13A).
mAuA: The lower current ranges, fuse is in the socket and very easy to replace.
COM: The common terminal for all ranges.
xxx: All other ranges.

Measurements

Volt and frequency
- Frequency counter and duty cycle do not requires a zero crossing
- At 0.1Vrms frequency input range is from 1Hz to 5MHz
- At 0.1Vrms frequency input range can be stretched to 0.8Hz to 8.2MHz, where it will show OL
- 1 VAC is 5% up at 120kHz
- Duty cycle works from 20% to above 80% at 100kHz with 1Vpp, precision is within 3.4
- Duty cycle works from 6% to above 80% at 10kHz with 2Vpp, precision is within 2.5
- Duty cycle is slow to show the final value.
- Max/min needs about 730ms to capture a voltage.
- Peak hold needs about 0.6ms to capture a voltage.
- Input impedance is 10 to 11Mohm on DC, AC has a capacitor
- DC mV range is high impedance below 1V, then it will drop to 200Mohm up to 3.3V, above this is goes down to 10kohm.
- AC mV range is high impedance below 3V, above this is goes down to 10kohm.
- Maximum rated voltage is 1000VDC/AC, but no overload voltage is specified for the mV range.
- Frequency input is around 10Mohm
- Rated overload protection for frequency range is 250V AC/DC
- A very audible alarm is sounded when mV or V range is overloaded
- A “high” DC voltage on mV AC will turn the display off.
- dBm mode default uses 600ohm, but can be selected from: 4, 8, 16, 32, 50, 75, 93, 110, 125, 135, 150, 200, 250, 300, 500, 600, 800, 900, 1000, 1200
Current
- On the current ranges there is an audible alarm when going above range, except on 20A range!
- mA range has a 0.5A/250V 5×20mm glass fuse (Manual says 0.8A/250V), that can easily be replace.
- 20A range has a 13A/250V 5×20mm ceramic fuse. Meter must be taken apart to replace fuse.
Ohm, Continuity, diode and capacity
- Ohm is 1.2V open and 0.86mA shorted
- Continuity is moderate in speed (About 50ms).
- Continuity beeps when resistance is below 46ohm (There is some noise up to 60ohm).
- Continuity is 4.1V open and 0.85mA shorted
- Diode range uses 3.1V, max. display is 2.97V at 0mA, max. current is 0.85mA shorted
- Diode and continuity is same range, it will always show voltage (Within 0.1V) and a open/shrt on the secondary display.
- Instead of a nS range, this meter has a high ohm range
- 90uF takes about 2 seconds to measure.
- Rated overload protection is 250V AC/DC
Miscellaneous
- Square wave generator has the following frequencies: 0.5Hz, 1Hz, 2Hz, 10Hz, 50Hz, 60.24Hz, 74.63Hz, 100Hz, 151.5Hz, 200Hz, 303Hz, 606.1Hz, 1.25kHz, 1.666kHz, 2.5kHz, 5kHz
- Square wave generator duty cycle can be adjusted in 1% steps, but 49% requires 98 button presses!
- Square wave generator has about 3.8kOhm in output impedance.
- A “high” DC voltage on temp will turn the display off.
- Power consumption is 1.2 watt in VDC with background light off. In diode with background light on it is 2.2 watt.
- When off the power consumption is 0 (Not all bench meters turns completely off).
- The meter has a auto power off function, but this is disabled when RS232 is on and it is on by default. The off function will not turn the power off, only the meter circuit, the meter will use 1.3 watt in this state.
- The meter usual need a couple of display update to reach the final value.
- Viewing angle is fairly good.
- Display updates around 4 times/sec
- Bargraph updates 40 times/sec, but is fairly low resolution.
- Backlight stays on when selected.
- Sockets are not deep enough for standard banana plugs to be fully seated, but they will make contact.
- Weight is 1400g without accessories.
- Size is 248 × 205 × 88mm.
Probes
- Probe resistance 38mOhm for one.
- Probe wire 87cm long.
- Aligator leads is 20mOhm for one.
- Aligator leads wire is 12cm long

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A look at the capacity measurement waveform.

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Square wave out on default setting.

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Highest frequency on generator.

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With maximum duty cycle, this required 49 presses on a button to get from 50 to 99%, there is no auto repeat or decrement button.

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Lowest frequency.

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The output impedance is about 3.8kohm.

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Frequency input resistance.

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The AC range works best up to about 560 volt, then it looses precision according to the specifications.

Software

The software is rather old and the newest Windows it works on is XP V1, a XP simulation on Win10 do not work.
It is possible to find the protocol on the internet for people that want to write their own software.

Tear down

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I had to remove four long screw at the bottom to open the meter, this is also required to replace the A fuse.

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Even though the meter is small for a bench meter, there is a lot of empty space inside.
It looks like the shipping of the meter has been a bit rough (Transformer is tilting).

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The power supply is a 9V DC regulator (IC10: LM7809). A significant part of the power consumption probably goes to the transformer and regulator.
The backplate has printing on both sides.

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The mains switch is also on the power supply. The RS232 interface circuit board is only to connect the cables to the DB9 connector, there is no electronic on it.

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The actual meter is on the front plate with two circuit boards on top of each other. The one at the back is the analog board with all the electronic hidden below a can. The 13A fuse is also here.

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I had to remove 6 screw to get the analog board out, 3 screws was connections to the input terminals, the other 3 was to standoffs in the front plate.

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And five more screws to get the digital section out.

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The front plate with all the buttons and terminals. The hole is for the power switch that is on a rod from the back of the meter.

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The large LCD display that is soldered to the circuit board (No zebra stripe), there is two leds for the backlight (D1 & D2).
Some of the labeling is interesting with AD0..AD3, this must be address/data with only a 4 bit data bus. This is for the ADC. The K signals is for range switching and controls relays.

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The digital board. The large chip is the LCD driver and RS232 data interface (IC5: FSUP01-003), besides it is a microprocessor (IC7: Holtek HT48R30A-1, 8bit 2kx14 program, 96 bytes ram). There is some EEPROM (IC6: Atmel 93C46 128 bytes) probably for calibration.
The RS232 interface is on the simple side, it is two optocouplers (LR & LS: COSMO 1010), because it is isolated power must be supplied by the RS232 handshake signals for the transmitter.
The datasheet for FS970x contains a typical schematic with the FSUP01 chip.

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At the input is a MOV across the voltage input (Very bad idea), there is also a large A shunt (Good idea with a large shunt). The large black round resistor next to the large shunt is a mA shunt and it is protected by D3 and Q16/Q17. The input protection for other ranges is handled by some PTC’s (PTC1..PTC4) and some transistor clamps (Q1..Q4).
The analog board has the ADC (IC1: FS9704 80000 count, 4 bit interface with 8 to 24 bit registers), RMS converter (AD737J) and a reference (LM385). There is two probably custom resistors (R4 & R5: Big black boxes). There is two trimpots and two trim capacitors for some calibration.
The range selection is done with 4 relays (K1, K2, K3, K4) and some CMOS switches (IC10 & IC11: HEF4053).
There is some voltage regulation on this board, both 6V (IC3: 70L806) and 5V (IC4: 7805)

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With a microprocessor with only 2k word program memory the amount of functions on this meter is fairly impressive.

Conclusion

There are a lot of details I do not like with the meter:

Missing overload protection on some ranges.
Overrange alarm will sound while the meter is auto ranging.
Duty cycle adjustment on square out requires way to many button presses.
Timer function is basically useless.
The capacity range only goes to 100uF
I am missing AC and DC at the same time.
Fuse is only 250V for a 1000V rated meter.
Combined diode and continuity
Min/max is fairly slow.
Temperature defaults to internal temperature, I want my probe temperature.
Some functions are blocking for each other, because they both need dual display.
The meter will not restart after a fast off/on cycle (It locks up), it need to be off a few seconds.
The user interface is not always logical.
Missing uA range.

But there is also a lot I like about the meter:

Good precision on VDC
Good large display when background light is on.
Lots of measurements.
The dual display is very well used.
It has average
Frequency out is at logical levels and can directly be feed to chips.
Peak hold is fast.
Auto hold.
True RMS and AC+DC display.
Cheap mA fuse, very useful on the bench with limited current and voltage.

The meter has nearly all the functions you could wish for.

Notes

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DMM Brymen BM27s

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Brymen is one of the good DMM manufactures and have a large selection of DMM’s in their program. This meter is a smart pocket meter.

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The meter arrived in a plain white box with a sticker (This is probably related to the dealer I bought it from).

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It contained the meter, a manual and a pouch for the meter.

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The probes are small without any text, but they do have tip covers.

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Meter in pouch.

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The range switch can be turned with one hand without the meter moving around.

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There is a list of the ranges on the back of the meter.

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Display

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The above picture shows all the segments on the display. It is missing the A symbol, this means the current range is lacking a A on the display.

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Meter is in auto mode and waiting for voltage or resistance.

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Voltage in AUTO mode, here I manually selected it (I do also need a new battery).

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Voltage in volt mode.

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Continuity mode with open and closed connection.

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Electric field detection.

Functions

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Buttons:

Select: Hold down to power on/off, press to select range (Se list below).

Rotary switch:

Auto V ohm: AUTO (VAC-LowZ/VDC-LowZ/ohm), Continuity, NCV, VAC-LowZ, VDC-LowZ, ohm, Frequency, Capacitance
V: VDC, VAC, Frequency
600ohm: Diode, Low ohm
uA: uA DC, uA AC

Input

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

Measurements

Volt and frequency
- Frequency input triggers around 1V.
- At 1Vrms input frequency range is from 2Hz to 14kHz in AUTO with Hz selected.
- At 3Vrms input frequency range is from 2Hz to 70kHz in AUTO with Hz selected.
- At 3Vrms input frequency range is from 1Hz to 70kHz in V with Hz selected.
- 1 VAC is 5% down at 2.6kHz in V mode
- Auto input requires 1VDC to select VDC mode.
- Auto input requires 1.7VAC to select VAC mode.
- Input impedance is about 5Mohm on voltage input, this includes frequency selection.
- Auto input impedance (LowZ) varies from a few Mohm at low voltages and down to 830kOhm at higher voltages.
- Frequency input on AUTO has 10Mohm below 1.5V and drops to a 1.5kohm above.
- Input rated to 600V AC/DC overload protection.
Current
- uA range is protected by a PTC
- Input rated to 600V AC/DC overload protection.
Ohm, Continuity, diode and capacity
- Low ohm mode needs about 0.3s to measure 100ohm, this is very fast
- Ohm needs about 2.5s to measure 100ohm in AUTO mode.
- Ohm is 0.16V open and 0.032mA shorted
- Ohm beeps when resistance is below 21ohm
- Continuity is quick (About 60ms) in AUTO with selected continuity.
- Continuity is fast (About 30ms) in Continuity/Low ohm mode.
- Continuity in AUTO beeps when resistance is below 130ohm
- Low ohm mode/Continuity beeps when resistance is below 170ohm
- Low ohm mode/Continuity is 0.47V open and 0.084mA shorted
- Continuity in AUTO is 1.3V open and 0.23mA shorted
- Diode range uses 1.3V, max. display is 1.000V at 0.062mA, max. current is 0.23mA shorted
- 2000uF takes about 52 seconds to measure
- Input rated to 600V AC/DC overload protection.
Miscellaneous
- Current consumption of meter is 0.9mA in most ranges, but AUTO VAC and VDC is 7.5mA due to the current to switch the LowZ resistor on.
- Meter works down to 2.3V where meter turns off, battery symbol show at 2.5V.
- Reading is stable until meter turns off.
- The meter need one or two display update to reach the final value.
- Viewing angle is good
- Display updates around 5 times/sec
- Will automatic turn power off in about 200 seconds when not used.
- Weight is 78g without accessories, but with batteries (Pouch is 35g extra).
- Size is 114 × 53 × 12mm not including probe wires or connection
Probes
- Probe wire is soft, thin and 65cm long.

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A look at the capacity measurement waveform.

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In auto mode the meter has a slight voltage on the probes and will pulse them sometimes.

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Frequency input resistance in AUTO mode, it is the logical frequency input.

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Frequency input resistance in V mode, it is the high voltage frequency input.

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Low current range has a 0.9uA offset.
2000uA range works up to 4000uA, but voltage drop is 5.6V
10nF capacitor range has a 0.5nF offset while measuring 1nF (Accuracy below 50nF is unspecified)
Mix of AC and DC voltage will confuse both AUTO and volt mode.

Tear down

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I had to remove 1 screws to open it.

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The back contains the buzzer and a bridge to connect battery to circuit board.

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The meter is shielded with holes for springs that connect to the buzzer and a switch pad (It is marked SELECT2 as can be seen below).

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I had to remove one locking ring and unclip the circuit board to take it out.

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The front has the LCD display, the range switch and part of the battery holder.

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The shield is glued to the circuit board in one corner. There are a lot of test points on this circuit board and not much else.
All the cut-outs are for better high voltage isolation.

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There is a good input protection with series resistors (R56 & R60: 2× 560ohm), PTC, fuse (FS1) and two spark gaps (SPG1 & SPG2). There are also some transistor pairs (Q3 & Q5, Q4 & Q4A, Q8 & Q9) for protection. The relay (U5: Cosmo KAQW414S) is probably the reason for the high current consumption in the Low-Z ranges (It requires some mA to turn it on). The Low-Z may be 3 resistors (R28. R29, R30: 3×330k). There is two input chains (R1A1, R1B1, R1C1: 3×3.3MOhm and R19, R24, R25: 3×3.3Mohm) and they must both be used simultaneously to get the 5Mohm input impedance of the meter.
The current shunt is a resistor (R42: 100ohm) with a transistor clamp (Q3 & Q5). The reason for the high burden voltage is not this resistor, but because it uses the normal input protection (R56+FS1+PTC).
The meter has revers polarity protection from the battery by a low forward voltage diode (D4A).
With all the automatic selection going on it is no surprise that there is a mux (U3: 74HC4053).
The main multimeter chip (U1) is hidden and probably read its calibration from U2 (Probably a EEPROM).

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Conclusion

The CAT rating is probably correct, the protection looks good and Brymen marks correctly.
The meter has a lot of ranges, but is a bit confusing to use, because some ranges exist in multiple positions on the range switch:
Ohm both exist in normal ohm and low ohm.
Voltage exist in Low-Z and normal voltage.
Frequency exist in both AUTO and V switch position.
Continuity can be done in ohm, continuity, low ohm and diode mode.

The usefulness of the high current range is fairly limited due to the very high burden voltage.
The low capacity range has very bad precision and is not rated.

The auto function is nice, but with all the above user interface issues it is not that easy to use all the functions.

Notes

This meter is probably sold in more or less rebranded versions.

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DMM Mastech MS8229

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This is a fairly cheap DMM with all common function and some environment functions.

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It arrived in a box with a picture of another meter, because the box is used for multiple models. Mastech has 3 models in the MS8229 series as can be seen on the back of the box and this is the “high end” model.

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

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The probes has removable tip covers. The CAT rating is marked on the tip and will change when the cover is removed.

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The plug is fully shrouded. The pin inside is shorter than standard probes.

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The meter includes a cheap thermocoupler.

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The tilting bale is stable enough to use the switch and buttons, but the meter may slide around on a smooth surface.

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The environment sensors.

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Display

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The above picture shows most of the segments on the display, not all environment segments are not included.

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Typical display during usage, it will show the number and what measurement is selected.
The display will always show humidity and ambient temperature, but they need a few second to initialize when powering on.

Functions

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Buttons:

Rel: Shows values relative to current value, will also select manual range. Press again to disable.
Range: Will disable auto range and change range, hold down to activate auto range again.
Select: Select the secondary ranges (VAC, AAC, continuity, diode, capacitance).
°C/°F: Select between Celcius and Farnheit
Hold/B.L: Freezes the display, press again to release, hold down to activate backlight (This will also activate hold, press again to relase hold).
Hz/Duty: Shows frequency and duty cycle in V and A ranges, changes to duty cycle in Hz range.

Rotary switch:

A: Current AC and DC, use SELECT to select AC
mA: Current AC and DC, use SELECT to select AC
uA: Current AC and DC, use SELECT to select AC
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Clik here to view.: Ohm, Diode, continuity and capacitance range, use SELECT to change between them.
V: Voltage DC and AC, use SELECT to select AC and use manual range to select mVAC
Off: Meter is turned off
Hz Duty: Frequency and duty cycle, for high bandwidth this selection must be used, it is only for low voltage.
TEMP: Temperature with thermocoupler.
dB: Sound pressure.
Lux: Brightness
x10Lux: Brightness, higher range. The display has a small x10 indication to show this range is selected.

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 and thermocoupler (temperature) input, the selector switch will change between two different shunts, it uses a PTC as fuse.
COM: The common terminal for all ranges.
xxx: All other ranges.

The terminals are not deep enough to cover standard banana plugs, but they do connect.
Each terminal has a light that will light up if a probe has o be inserted and flash if the probe is in the wrong terminal. This feature is very nice.

Measurements

Volt and frequency
- Frequency counter and duty cycle requires a zero crossing on AC, DC.
- Frequency range input works with signals in the -3 to 6 volt range.
- At 100mVrms input frequency range is from 0.6Hz to 280kHz
- At 1Vrms input frequency range is from 0.6Hz to 40kHz
- Input impedance is 10 to 11Mohm on DC, AC and ACmV
- Duty cycle works from 10% to 90% at 1kHz with 4Vpp, precision is within 3.3
- Duty cycle is slow to find the final reading.
- mVDC range is high impedance up to 1.5V then it drops to 10Mohm
- 1 VAC is 5% down at 2.5kHz
- High DC voltage may block for AC readings.
- Frequency input resistance is 1Mohm at 1V but will increase to 5Mohm at 25 volt.
- Rated overload protection for frequency range is 250V AC/DC
Current
- mA & uA range uses a PTC as fuse, i.e. it will automatic recover when over current is removed.
- uAmA is protected by a 500mA/250V PTC (Automatic fuse)
- A is protected by a 10A/250V 6.3×32mm fuse.
Ohm, Continuity, diode and capacity
- Ohm needs about 3.4s to measure 100ohm
- Ohm is 0.42V open and 0.19mA shorted
- Continuity is slow in speed (About 130ms).
- Continuity beeps when resistance is below 42ohm (There is some noise for a few ohms more).
- Continuity is 0.44V open and 0.19mA shorted
- Diode range uses 1.7V, max. display is 0.999V at 0.31mA, max. current is 0.72mA shorted
- 100uF takes about 16 seconds to measure.
- Rated overload protection is 250V AC/DC
Miscellaneous
- Sound meter shows 16dB at low levels (like 60dB), but will show too high at 100Hz
- Light meter is fairly precise with incandescent, but is not filtered correctly.
- It is possible to get out of sync on °C/°F between TEMP and environment temperature.
- Current consumption of meter is 2.5mA (30mA with backlight and 5mA with two input terminals on)
- Display show wrong value at 2.8V on battery, battery symbol show at 3.6V.
- Reading will change slightly with battery voltage: 3 count on a 3.0V reading from 4.5V to 3.5V.
- Backlight brightness will very with voltage, but is works down to the meter shows wrong values.
- The meter usual need a couple of display update to reach the final value and may show a too high value during that time.
- Viewing angle is fairly good, except from the top
- Display updates around 2.5 times/sec
- Backlight will not turn off, even when meter turns power off after 35 minutes.
- Will automatic turn power off in about 35 minutes.
- Sockets are not deep enough to cover standard banana plugs, but they will make contact.
- Sockets will light red when a probe is supposed to be on it.
- If a probe is plugged into the wrong socket the correct one will flash red and the buzzer will sound.
- Weight is 422g without accessories, but with rubber sleeve and batteries.
- Size is 192 × 93 × 55mm with rubber sleve.
Probes
- Probe resistanse 25mOhm 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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Tear down

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Four screws and the back could be removed.

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Two more screws and the circuit board could be lifted out, but I also had to remove two screws in the environment sensor unit to remove that.

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Holes and white dome for sensor unit.

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There is a lot of wires between the sensor unit and the circuit board, all with the same 3 pin connectors.

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Sensor unit has two diodes for temperature measurement, a humidity sensitive resistor , a photo diode and a microphone.

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And there is also electronic for signal conditioning and adjustment.

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It is a fairly complicated circuit, I will not try to descibe much of the circuit (It is difficult to find data on the different chips).
Some obvious details:
The two resistors that is visible below the 10A input terminal are the mA and uA shunt and the diodes (D3..D6) below the input circuit board are protection for them. The 10A fuse is marked 250V on the circuit board, this do not really match with the 1000V input marking.
The two resistors (R21A & R21B 2×5Mohm) are probably an input resistor, but distance are very low for any high voltage. Close to them is the only PTC (R25) in the circuit.
The meter is adjusted with trimmers, this is not the most stable solution, but can be nice for DIY calibration.

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The front shield is mounted with two screws at the front, the lcd display is connected with the orange zebra stripe.

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There is nothing on this side of the circuit board, except switches and connection to the display.

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The light on the four input terminals is controlled with a PIC16F54 processor, the two led around each terminal and the switches on the other side. The big brown part is a PTC that is used for overcurrent protection on the mA and uA range.

Conclusion

Generally the DMM calibration is very good on this DMM, i.e. within a few count, but the environment measurements are not that impressive, but except for sound works acceptable.
The automatic mA/uA fuse is nice, but it means a very large voltage drop when measuring current in the high mA range (Use A range instead).
Generally it is a nice meter for occasionally use and and can work well on a workbench, but it is not for high voltage and high current. As usual the CAT ratings is way too high.

Notes

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DMM Brymen BM869s

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This is the top Brymen meter with very high precision and PC connection (Must be bought separately).

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The meter arrived in a cardboard box that is used for the two top models, on the back is a table comparing them.

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The box included the meter, two probes, a thermocoupler (Meter supports two) and the manual (It can also be downloaded).

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Probes are branded with B.T.C. and has removable tip covers.
The probes are rated for up to CAT IV 1000V like the meter.

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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 or the buttons is pressed.

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The PC connection is here with an optical link.

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The tilting bale can be moved a bit and then be used to hand the meter on.

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The rubber sleeve must be removed to replace the battery

Display

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The above picture shows all the segments on the display.
There is a 4 digit, a 6 digit display and a bargraph. Only 5 of the 6 digits are usual used, in DCV it is possible to activate the last digit. The small display and the bargraph will only be used in some ranges, see end of this chapter.

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Normal DC voltage with voltage and bargraph.

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In some AC modes the small display will supplement the large display.

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With this display the meter could not maintain the bargraph.
The bargraph will not be show when the secondary display shows voltage or current.

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Current with a 4-20mA percent supplement.
Dual and single display functions (After / is small display):
VAC VFD: VAC/Hz, Hz/VAC
VAC: VAC/Hz, dBm/Hz, Hz/VAC
VDC: VDC, VDC/VAC, DC+AC/VAC
mVDC: mVDC, mVDC/mVAC, mDC+mAC/mVAC, Hz, Duty Cycle
mVAC: mVAC/Hz, dBm/Hz, Hz/mVAC
Temp: T1, T2, T1/T2, T1-T2/T2 (Use RANGE to select)
mA: mADC/%4-20mA, mADC/mAAC, mDC+mAC/mAAC, mAAC/Hz
A: ADC, ADC/AAC, DC+AC/AAC, AAC/Hz
uA: uADC, uADC/uAAC, uDC+uAC/uAAC, uAAC/Hz

Functions

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

Select (Yellow): Select between the different modes on each position of the range switch, hold down to activate background light. Meter will remember the selection and use it next time the range is selected.
Range: Switch to manual range and select range, hold down to activate automatic ranging again. In dB mode this button will select reference impedance from 20 different values, in temperature mode it will select different combinations of thermocouplers.
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Clik here to view.: Shows values relative to current value. In VDC Hold down to activate 500000 count mode.
Crest: Peak mode, will record and show fast min/max. Use button to change between min/max. Hold down to end mode.
Rec: Minimum/maximum mode, will record min/max values. Use button to change between actual/max/min/average. Hold down to end mode.

Rotary switch:

Off: Meter is turned off.
VAC VFD: Measure AC voltage with a low pass filter, will also show frequency.
VAC: Measure AC voltage, frequency and dB
VDC: Measure DC voltage, AC voltage and AC+DC voltage.
mVDC: Millivolt range, measure DC voltage, AC voltage, AC+DC voltage, frequency and duty cycle.
mVAC: Millivolt range, measure AC voltage, frequency and dB
T1 T2: Measure temperature with one or two thermocouplers, can also show difference between them.
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Clik here to view.: Resistance and continuity, the nS makes it possible to measure very huge resistance values.
A mA: This is either mA or A depending on where the probe is connected. It will measure DCA, ACA, ACA+DCA, frequency and 4-20mA
uA: The uA range. It will measure DCA, ACA, ACA+DCA and frequency.

dB reference impedance: 4, 8, 16, 32, 50, 75, 93, 110, 125, 135, 150, 200, 250, 300, 500, 600, 800, 900, 1000, 1200

Input

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A: High current, maximum current is 10A, also ground for second thermocoupler.
mAuA: The lower current ranges and + input for the second thermocoupler.
CON: The common terminal for all ranges.
xxx: All other ranges.

Measurements

Volt and frequency
- 500000 mode do not increase precision, only resolution. Normal readings do not round the extra digit.
- Frequency input has a trigger point around 1.5V
- At 1Vrms frequency input (mVAC) range is from 2Hz to 300kHz
- At 3Vrms frequency input (mVAC) range is from 2Hz to 2.8MHz
- At 100mVrms input on mVAC range, frequency range is from 2Hz to 800kHz
- Duty cycle works from 3% to 99% at 100kHz with 4Vpp, precision is within 2.5
- 1 VAC is 5% down at 350kHz (RMS will not work at the frequency).
- 1 VAC with LPF (VFD) is 5% down at 530Hz.
- Auto range works when doing min/max, peak and relative.
- Max/min (Rec) needs about 350ms to capture a voltage.
- Peak (Creast) needs about 0.7ms to capture a voltage.
- Large AC values on DC ranges will prevent the meter from showing a value, except if dual display AC and DC is selected.
- Input impedance is 10-11Mohm on DC
- Both AC input has a capacitor
- The DCV & DCmV range has two paths: Directly DC volt and True-RMS volt, they will not show exactly the same value. The 500000 readout can only be selected in the direct DC mode.
- mV DC/AC has 10Mohm input impedance up to about 3V, then it drops to 20kohm at 10 volt and 4kOhm at 35 volt.
- Frequency input is 10Mohm up to 3 volt then it drops to 20kohm at 10 volt and 4kOhm at 35 volt.
- Rated overload protection on V ranges is 1100VDC/VAC and 12kV transient.
- Rated overload protection is 1000VDC/VAC and 12kV transient in mV range .
Current
- Overload protection in uA and mA: 0.44A/1000V 10×38mm fuse
- Overload protection in A: 11A/1000V 10×38mm fuse
- DCmA can show a secondary display with percent of 4-20mA range
- There is an audible warning and display shows “InErr” when using non current ranges with a probe in mAuA or A input.
Ohm, continuity, diode and capacity
- Ohm needs about 1.9s to measure 100ohm
- Ohm is 1.15V open and 0.38mA shorted
- Continuity is very fast (Below 10ms).
- Continuity beeps when resistance is below 94ohm
- Continuity is 2.9V open and 0.38mA shorted
- Conductivity (nS) is 1.15V open and 1.1uA shorted
- Diode range uses 2.94V, max. display is 2.0000V at 0.12mA, max. current is 0.38mA shorted
- 11000uF takes about 11 seconds to measure.
- Rated overload protection is 1000VDC/VAC and 12kV transient.
Miscellaneous
- Current consumption of meter is 5mA-7mA (30mA with backlight)
- Meter works down to 5.6V where it says “InErr”, battery symbol show at 6.3V.
- The meter reading is stable until it reports “InErr”.
- Backlight is stable until meter reports “InErr”.
- The meter sometimes need a couple of updates before the reading is fully correct.
- Viewing angle is good
- Display updates around 5 times/sec (1.25 times/sec in high-res mode).
- Bargraph updates 60 times/sec
- Backlight will turn off in 15 seconds
- Will automatic turn power off in about 17 minutes without any warning.
- Standard probes fits perfectly into sockets on meter.
- Weight is 642g without accessories, but with batteries.
- Size is 210 × 103 × 64mm.
Probes
- Probe resistance 26mOhm 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, this is similar to mV

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Software

The software must be bought separately.

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The box only includes a cable and a CD. The CD contains software for many different meters and also files describing the data format (It is the display segments, not digits that is transmitted).

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The opto adapter has two leds and some mechanic to lock it securely in place.

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Here it is mounted on the meter.

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The software is one top bar and initially four independent windows.

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Here I am connected to the meter and read data.
The data can be saved from the chart window in either an internal format or exported to a image or CSV file.

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The different windows in the meter software can be closed and moved independent, except the title and command bar.

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Here is the export dialog. There is another menu to adjust the logging interval.

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The CSV file is fairly easy to read.

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And if the meter is using the dual display it will log two sets of data for each line.

Tear down

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4 screws and the front could be removed (This time it was not the back). The screws do not fall out, but stays in the holes.

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There are pads for 8 buttons, but the meter only has 6 buttons? There is also space for an extra chip.

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On this image it is possible to see that the missing buttons are marked UP and DOWN

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To get the electronic out I had to remove one more screws (There are holes for two).

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The back of meter is shielded and the buzzer is mounted outside the shield.

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On this side there are a couple of springs for connection to the shield and buzzer and also two leds for the computer link.

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I had to remove four screws around the range switch to take the two circuit boards apart.

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Around the center fuse (0.44A) is four diodes for protection of the mA and uA shunts, there is also the input terminal sense resistors (R6abcdef: 6×2Mohm). The ones for the 10A range is below the 10A fuse.
The voltage input has two paths with resistors (R1 & R2 and R3 & R4) each followed by a ptc (PTC3 & PTC?) and clamped to minus by some MOVS (SPG1 & SPG2 + SPG3). There is also 3 pairs of transistors (Q3 & Q4, Q5 & Q6, Q7 & Q8) that can be switched in.
The voltage divider and multimeter chip is below the shield, that is soldered to the circuit board. The big capacitor (C1) is the AC input capacitor.
Some interesting chips are the reference (U4: REF43G), a analog switch (U11: 74HC4053D), a voltage converter (U7: HT7660), a OpAmp (U14 & U15: MCP602I), rms to dc converter (U12: AD636JHZ).

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Two screws more and I could pull the display off.

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On this board is the main processor and a EEPROM to store calibration (U5: S24CS04A)

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Only the connectors and the range switch on this side. The range switch is a bit interesting, it has 8 circles of contact points, but in the range switch there is only switches to cover 4 circles?

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Conclusion

This meter has a lot of protection and mounted the right way, it do also have very large fuses.
All the common ranges are present and also a lot of extra functions like Peak, Average, Dual-display, AC+DC. This makes it a very universal high end meter with just about any desired function. In the volt ranges the range switch is a bit overloaded (All 5 volt ranges can measure AC) and it may take some time to get it straighten out what range to use for what with AC, all other ranges are logical enough.
The meter is not really specialized for electrician, industrial, HVAC, audio or electronic, but is mostly perfect for all of it (The missing Low-Z mode may give a minus point for some areas).

Notes

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DMM Mastech MS8216

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This is a small pocket DMM with voltage, frequency, ohms and capacity.

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The meter was in a clamshell pack. On the back is a the specifications.

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In the pack was the meter and a manual in English.

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The probes are small and they are not round, but ellipse shaped.

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The probes are directly connected to the meter, no plugs and sockets.

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The range switch is easy to turn, but the detents are not very strong and it is very easy to place the switch between ranges.

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A pouch is included.

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Two screws must be removed to get battery access.

Display

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The above picture shows all the segments on the display.

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Typical display during usage, it will show the selected range and value.

Functions

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Buttons:

Rel: Store current display value and show all new values relative to this value.
H/D: This is short for Hz/duty cycle and will show frequency and duty cycle in both DC, AC and frequency mode.
D-H: This is the hold button and will freeze the display reading, until pressed again.

Selection of Rel and Hz/duty will disable auto ranging and it stays disabled

Rotary switch:

Off: Meter is turned off
VAC: Voltage AC, frequency and duty cycle.
VDC: Voltage DC, frequency and duty cycle.
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Hz: Logical frequency input.

Input

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

Measurements

Volt and frequency
- At 1V rms input on frequency the counter range is from 2Hz to 50kHz
- At 2V rms input on frequency the counter range is from 0.6Hz to 100kHz
- At 5V rms input on frequency the counter range is up to 290kHz
- Duty cycle works from 15% to 90% at 1kHz with 4Vpp, precision is within 3.0
- Frequency inputs do not need a zero crossing.
- 1V AC readings is 5% down at 2kHz
- Voltage input impedance is 10-11Mohm,
- mV input impedance is high below 1.5V and drops to 10Mohm above
- Frequency input is similar to mV input.
- Input protection is 600V AC/DC for voltage 250V AC/DC for frequency.
Current
- Meter cannot measure current
Ohm, continuity, diode and capacity
- Ohm needs about 3.4s to measure 100ohm
- Ohm is 0.42V open and 0.17mA shorted
- Continuity is moderate in speed (100ms)
- Continuity beeps when resistance is below 55ohm
- The beeper volume is very low.
- Continuity is 0.44V open and 0.17mA shorted
- Diode range uses 1.5V, max. display is 0.999V at 0.2mA, max. current is 0.55mA shorted
- 190uF takes about 40 seconds to measure.
- Rated overload protection is 250 VDC/VAC
Miscellaneous
- Current consumption of meter is 0.8mA except AC where it is 1.4mA
- Meter fails below 1.4V, battery symbol show at 2.4V.
- Readings will drift about 2 count when from when battery symbols shows to the meter fails.
- Viewing angle is good, except from top
- Display updates around 2 times/sec
- Will automatic turn power off after about 15 minutes
- The meter often need many display update to reach the final value.
- Weight is 82g without accessories, but batteries.
- Size is 110 × 78 × 13mm.
Probes
- Probe wire is a bit thin, they are 31cm long.

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Capacity measurement waveform.

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Frequency input resistance in voltage frequency position, V and mVDC is similar.

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Frequency input resistance in voltage AC position.

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Lowest capacity range is sometimes out of tolerance (Up to 8%) and next time I measure the same capacitor it is inside tolerance.

Tear down

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I had to remove two screws, to open it, this is also required when replacing batteries.

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The battery holder is for two button cells.

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I had to remove 6 screws before I could get the circuit board out.

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The buzzer is mounted on the frontplate.

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On this side there is only two capacitors and holes for adjusting the 3 trimpot (VR1, VR2, VR4).

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On the input is a PTC (R24), it is not used for all ranges. The main input resistor (R21 & R’21 2×5Mohm) goes directly to the multimeter chip. My guess is that the input protection is a single transistor (Q1), it looks like the 5 diodes (D3..D7) is used for coding range switch to multimeter chip and the two other diodes (D1 & D2) may be rectifier circuit for AC measurement where VR2 is used to adjust it with.
The multimeter chip (IC1 CS7721) handles everything in the meter.

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Conclusion

The meter is specified at 600V, but the ranges can only handle 250V in overload.

The meter has about the expected functions for a pocket meter without any current ranges. There is a few problematic areas with it: Range switch must be carefully placed in the correct position it do not snap into position, buzzer is difficult to hear, duty cycle is low performance and the lowest capacity range is not completely reliable.

Notes

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