I know this comes up a lot.
If I hold my multimeter probes in my hands, I get a DC voltage. When I let go I get 0.000V. Holding the probes it ranged between -400mV and +250mV while I tested. It changes oddly too. It sits stable for a few seconds then climbs or drops for a few seconds and stabilises for a while before moving again.
That's not the weird part. It seems not to matter where I put the probes. If I hold one in each hand or if I hold both on the same finger the voltage is around the same range. I event stuck both in my mouth and I got similar voltages.
I tried touching different things around me and it didn't change the voltage, although I didn't try an actually electrical connection or earthed fixture.
If you do this on a scope is it just noise? Does my body cause a DC offest to the normal electrical field around me that normally appears as noise on scopes, amplifiers, etc. etc. What determines that voltage offset? Does it tell me anything if it's high or low?
Even then how can the voltage exist at any point across my body... is it just an artefact of body capacitance messing with the meter?
BTW, when I google this I get crack pot bullshit about EMF and grounding yourself in bed. LOL
When you use a meter (or any test instrument) it becomes part of the circuit. Never forget that.
As a simple check to verify if my scope still works, and the probe is connected to the right channel, I often touch the tip of the probe.
It usually picks up the local 50Hz, and with an amplitude can be multiple volts.
A bit of diode operation can maybe be introduced by any contact of dis similar materials.
Then there are thermocouples which generate a DC voltage (And can even deliver a significant current. Thermopiles have been built with multiple kilo watts ofoutput).
Regular DMM's have an input impedance of 10MOhm, but it can be higher. With such impedances it's easy to pick up all kind of stray noise.