Why isn't there a voltage when touching different batteries with a multi meter?

  • Thread starter jaydnul
  • Start date
In summary, to measure voltage using a multi meter, you need a complete circuit for a small current to flow and charge the input capacitance of the DMM. An exception to this is if the DMM is on AC voltage measurement and the two leads are held in your hands, which may result in a small AC voltage measurement due to AC mains noise.
  • #1
jaydnul
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So i was dinking around with my multi meter and i noticed that if you touch the positive end of a battery and the negative end of a different battery, there isn't a voltage being measured. Why is that. I would think that an excess of electrons would want to rush to any area that had a depletion of electrons, even if it wasn't in the same battery.
 
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  • #2
lundyjb said:
So i was dinking around with my multi meter and i noticed that if you touch the positive end of a battery and the negative end of a different battery, there isn't a voltage being measured. Why is that. I would think that an excess of electrons would want to rush to any area that had a depletion of electrons, even if it wasn't in the same battery.

You need a complete circuit to measure a voltage. A small current has to flow to charge up the input capacitance of the DMM and to drop a voltage across the input resistance of the DMM. Without a real complete circuit, you don't have that.

An exception to that is if you put your DMM on AC voltage measurement, and hold the two leads with your two hands. You will likely see a small AC voltage, which is from AC mains noise coupled capacitively into your measurement...
 

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