Electronics > Metrology

DMM does not stabilize when measuring resistance

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pwnell:
I know this is user error, but why can I not get a stable reading from a 34465A DMM using 2 wire or 4 wire on a 1kohm resistor?  I have 10 PLC, yet the value ranges from 0.982817 to 0.982920 … this seems more than the spec allows for. The resistor is not in circuit.

It takes about 2 minutes to reach some form of stable value.

gamalot:
What kind of resistance are you measuring? What kind of test leads are you using? How long did you wait for the reading to stabilize?

The test voltage in the 1 kiloohm range of the 34465A is 1 volt. You may need a little time to warm up the resistance under test.

bob91343:
With that kind of resolution you can't ignore thermal emf.

pwnell:
It is a 1k 1% carbon resistor. The meter says it uses 1mA on the 1k ohm range.  It feels very cool to the touch. Thermocouple says resistor is 1C below room temp after 5 minutes, yet value still fluctuates.

gamalot:
I don't have any carbon film resistors in my hand, so I can't repeat your experiment. However, I think your multimeter is worth testing it with a better resistance.

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