Fluke 8520A reading drifts

[johngalt47]

I bought this 5 1/2 digit meter a few years ago and it is ok except that trying to read microvolts is impossible. For example, this afternoon it is drifting from .2 to .5 mV DC and won't "sit still" no matter what.

Could it be an A/D or D/A converter or ???

[DF96]

Microvolts AC can pick up hum fields. Microvolts DC can get thermoelectric or contact potential effects.

[johngalt47]

Ok, so what method should I use aside from building a Faraday cage to combat the effects of hum from other sources?

[DF96]

For low level AC you need filtering, so the meter only sees the signals you are interested in. As well as hum there is also all the RF around in a typical location. 3 1/2 digits is good enough for most purposes, and don't believe any figures below a few mV.

[lepomis]

I have that same unit. I don't have a drift problem with either AC or DC. However, I have no idea if those last few digits are correct or not Does the unit pass it's 'self test' ?

Originally Posted by johngalt47

I bought this 5 1/2 digit meter a few years ago and it is ok except that trying to read microvolts is impossible. For example, this afternoon it is drifting from .2 to .5 mV DC and won't "sit still" no matter what.

Could it be an A/D or D/A converter or ???

[johngalt47]

I don't know...I've never run the self test. I will say that on lower value resistors it is rock solid.

[asmith]

I bet your in a high RF area, and thats what it's reading. Try shorting the inputs, right at the input and see what it reads.