Test/review of DMM Innova 3320

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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