Electronic – Multimeter giving seemingly inconsistent voltage readings

multimeter

I am trying to use a digital multimeter to measure a house solar panel installation. I'm just learning, but I can't find a good answer to my problem.

I tested the voltage on a 1.5 AA battery and as I moved the knob to higher voltages (from 200 mV to 1000 V) I get very divergent readings:

  • 200 mV : 1 (overloaded)
  • 2000 mV : 1580
  • 20 V : 2.56
  • 200 V : 12.4
  • 1000 V : 111

I don't know if I'm wrong, but I was thinking that as I increase the max voltage I'd get smaller values, but this jumps from 1580 to 2 then 12 and then 111, the pattern doesn't seem to grow evenly in the last 3 values either.

My original goal was to measure voltage in what was to be a 12 V installation, I got these readings:

  • 20 V : Overloaded
  • 200 V : 105+
  • 1000 V : 935+

I take it has more than 20 V, but the other readings don't make sense so I don't know how to interpret them.

Am I missing something, is there something I don't know?

Best Answer

First, if you don't know what voltage you are dealing with, you should set your multimeter to the highest voltage range available and go down until you get an acceptable accuracy.

Failing to do so, it is quite possible to damage your multimeter with a voltage 10x the range or more. It may as well be safe - depending on the multimeter. You didn't say your multimeter model.

In your particular case, it looks like your multimeter is broken or you are doing something profoundly wrong.

A sane multimeter connected properly to a fresh 1.5 AA battery will show:

200 mV : 1 (overloaded) - CORRECT
2000 mV : 1580 - MAYBE CORRECT
20 V : 2.56 - WRONG, it should be 1.58 or near it.
200 V : 12.4 - WAY TOO WRONG, it should be around 1.6
1000 V : 111 - if you can touch it without dying or at least swearing out loud, it is not 111V

What could be wrong?

  1. Multimeter battery is depleted. Some of these have "low battery" indicator while others don't have one. A lot of $10 multimeters will show "low battery" if the battery is near end and not show anything about the battery if it gets even lower.

  2. You are using AC setting for 20/200/2000 range instead of DC and the multimeter is one of those for $10

  3. You have a great deal of electromagnetic interference from other power equipment in your place.

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