Digital multimeter wrong current reading

[wysiwyg]

Hi carl, I did a new test this morning. I disconnected the positive from the battery and connected my regular multiimetre in the circuit. Then, on the fuseblock, I removed all fuses beside the water pump and turned it on. The reading was 1.7A. Still different from the digital one.

[wysiwyg]

Oh and for the lights, its all led. Same issue here, the digital multimeter will read 0.06A for one light switched on and my regular multimeter will read 0.03A (seems like its always reading X2 on the digital).

[CarlD]

Sounds like a calibration issue.

[wysiwyg]

Wow Carl, believe it or not but you last message seems to have solve everything :-) I checked on the amazon page and found this info in the description:

***
-Testing range setting
Long press button till the display shows a "Curr"(on lower left corner) and a current rate "50A/100A"; loosing the button and short press to choose 50A/100A.
***

I have set it to 50A (which is the one I bought) and then, the current is now accurate on everything. Also, when I plug my Propane Detector, it no longer bips... To be honest, im not sure to understand how this little setting fixes everything.

Anyways, thanks alot for taking the time to answer. Really helps!

[wysiwyg]

After several tests, my propane detector will bip red and green once installed in the trailer. When plugged directly onto the battery, it seems fine.

But other than that, the current reading works perfectly. Maybe my propane detector is defective? Not sure what other tests to run with it.

[Byron Kinnaman]

Maybe, maybe not.
All digital meters have a ±1 for the lowest or last digit. Meaning a reading of .06 is someplace between .05 and .07. That doesn't take into account the tolerance if meter circuitry. You'll have to read the specifications to determine that.



One of major problems is assumptions. Assuming that your meter is accurate to what ever level you're trying to measure, is a usual erroneous assumption when dealing with electricity. In the above is both meters have a 5% of reading tolerance add to that the ±1 digit and it's possible to have apparent errors. The best way to determine is to read the specifications.



Another assumption is when you measure current by measuring voltage across a shunt is that your meter is of a high enough impedance (resistance) to not have a significant effect on the reading.



have fun

[wysiwyg]

Hi Byron,

Thanks for your answer. What I meant is that, since I switched the device from 100A to 50A, the reading were split by 2. So now, when using the pump, it reads 1.7A (exactly what its suppose to be from the manual). Also, my regular multimeter also reads 1.7A when added in the circuit. I feel its safe to assume its working properly now?

Thanks and have a good day

[Paul O.]

Originally Posted by CarlD

Sounds like a calibration issue.

Well, this was an interesting thread. It is great that Carl's suggestion led to successful resolution, even though strictly speaking it is not a calibration issue, but rather a range selection issue.

[CarlD]

I just got back from my camp. I am glad you solved your problem your ammeter issue. Regarding the CO2 sensor, perhaps you stated in an earlier reply, but what does the red/green flashing mean? Is the voltage polarity correct at the sensor? I really don't know much about the sensors, but these are a couple basic trouble shooting items.

[CarlD]

Olivier, shunts are low resistance precision resistors. They produce a low voltage signal proportional to the current. The output is usually millivolts/amp. I would think the device has this written on it some place. If it does you can set your DMM to millivolts and read the voltage/current directly.