Help Me Understand My Resistance Measurement Error?

[clansd99]

Hi all,

I've got a WEIRD issue testing the resistance of various 1/4W resistors with my multimeters.

I initially thought my BM235 meter was busted, since any resistors over around ~10kOhms measured by hand with my probes across the leads were way off from their stated values (which were verified with my component tester). For my birthday I ordered the 121GW and figured the matter must be solved so paid no more attention - until recently.

When measuring resistors 10k and up with the 121GW the other day, I realized they were quite off! Generally LOWER in value than I would expect, by a significant amount. I figured there was no way the same issue would crop up with a second meter and it must be an error in my test setup.

In the end, I found that if I connected the resistors up to the meter via a pair of test clips, the problem vanished. But, measuring any resistors over around ~10kOhms by hand with a standard probe pressed onto the leads causes the issue mentioned above.

I don't remember having this problem in the past - what's going on here? In particular, why are the measured resistances LOWER than their real values?

Thought this might be an interesting topic for discussion and that (hopefully) a lot of people could learn from this.

[EEEnthusiast]

your hand resistance is coming in parallel with the resistance being measured and that reduces the overall resistance.
Ensure that you are not touching both the leads of the multimeter when measuring the resistance.

[clansd99]

your hand resistance is coming in parallel with the resistance being measured and that reduces the overall resistance.
Ensure that you are not touching both the leads of the multimeter when measuring the resistance.

Yes you must be right! I just measured the resistance just pressing the leads against my fingers to be ~0.6MOhm, which when put in series with the resistors in question gave exactly the numbers I was seeing. Thank you!