Question about a reading on a multimeter

Thread Starter

MrZeus

Joined Mar 8, 2009
3
Hi guys, I'm not too sure if this is the right place to ask about this so I apologize if it's not in the right place.

Anyway, I just got out a multimeter that I forgot I had and noticed that when on the VDC setting, even when the connectors aren't touching anything, it reads something like 0.5 mV. I'm just curious if this is actually just some ambient voltage in the air or something. I just had a physics course on this kind of thing but I'm still unsure on this. If someone could help me out, that'd be great, thanks!
 

mik3

Joined Feb 4, 2008
4,846
It can be due to radio waves, noise inside the multimeter's circuit, inaccuracies of the multimeter's components etc.
 

hobbyist

Joined Aug 10, 2008
887
If it is a digital meter. I think the term they use is "phantom readings"

If you put the probes to a solid voltage source you should get a steady reading at least in the range of voltage being measured.
 

DonQ

Joined May 6, 2009
320
Try it with the probes touching each other firmly. Better yet, get a shorting plug, a small block with two banana plugs at the right spacing. Even with the long leads shorted together, they are a big antenna. A shorting block gets rid of that.

As far as trusting any readings of 0.5 mV... Try measuring the same thing with two separate meters sometime and you may start to just ignore fractional millivolts.
 

flat5

Joined Nov 13, 2008
403
If it is an analog meter, before you turn the zeroing screw breath on the plastic or glass to remove static charge. Sometimes this will drop the needle to zero.
 
Check the model accuracy on the manual from manufacturer. Depending on how old it is, the manufacturer dont guarantee .1mV. Also check if they can be relacalibrated which may reduce the noise.
 

mik3

Joined Feb 4, 2008
4,846
MrZeus,

You have to understand one thing:

Electronics are not perfected but you modify/adjust the parameters to achieve the best results for each application.
 
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