Ohmmeter in multimeter gives inconsistent or high values

Thread Starter

ren_zokuken01

Joined Aug 17, 2016
6
When I start using my multimeter fresh off, when I short my probes or when measuring very low resistances (200 ohm range), my multimeter would initially give fairly high values, ranging from 15-40 ohms. Then after it has "warmed up" after testing with different higher resistances, say 120 ohm, and such, when I short it again it goes down to 0.6 - 0.3 ohms, which is the lowest I've seen it go. Sometimes when I use the beeping continuity tester is used first, it seems like to de-stabilize it, in which case I wait until I can use the ohmmeter again. Sometimes it's as if switching from the continuity tester back and forth re-stabilizes it. I'm not sure.

Using the continuity tester first off and looking at the value it puts on the screen gives the same behavior, though I notice that it seems to stabilize more quickly.

It's possible that the dial is faulty as since day 1, sometimes it would register at the last notch I turned it all the way. Say I was at the 2Meg ohm range and then I move it to 200 ohm, it would that think it's at 2k ohm range, until I re-turn the dial up and then down again.

There has been instances when in my hurry, I measured voltage when the dial was still in resistance, though when I made these mistakes the voltage was always not that high, if I remember correctly. Usually around 5-16V or something.
 

MrAl

Joined Jun 17, 2014
7,455
Hi,

Well one culprit could be the selector switch. They have been known to go bad because of the constant use. You could try switching it back and forth a few times and see if that helps as it may help clean the contacts. Sometimes the selector switch will not settle into the selection notch right either so you have to move it a little. It could also be the leads which may not have good continuity themselves.
 

ErnieM

Joined Apr 24, 2011
8,029
Is this a digital or analog (with a moving meter) type of meter?

When is the last time you checked or changed the battery?
 

crutschow

Joined Mar 14, 2008
24,704
Sometimes the sides of the probes can have a high resistance when you touch them together due to an oxide coating.
Try shorting the two probes together with alligator leads or applying the probe points to a piece of aluminum or copper.
 

ErnieM

Joined Apr 24, 2011
8,029
An analog meter also uses an internal battery to drive the resistance reading.

The advantage there is you can use the very same meter to check the battery voltage. Not so with a digital meter.
 

crutschow

Joined Mar 14, 2008
24,704
Analog meters only use the battery to check resistances. So you take the battery out and test it.
Okay, I see what you are saying.
But you can also measure the battery in place in a digital meter.
However since the battery is normally floating with respect to the meter ground, you need to measure each terminal using the plus lead only and add the voltage magnitudes together.
 

MaxHeadRoom

Joined Jul 18, 2013
20,403
Analog meters only use the battery to check resistances. So you take the battery out and test it.
My Fluke gives all kind of weird readings on most ranges when the battery is low, before the battery warning icon comes on.
I helped an electrician that mentioned to me he was getting 240vac readings where he would expect 120vac.
After I told him to change the battery it fixed it!
Max.
 
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