DMM resistance test, shows abnormally high values

[sdancer75]

Hi,

This is my spare "mobile" DMM that I am using out of home for emergency situations. I always store it in my car.

Lately, I noticed that sometimes -but not every time- it shows high resistance but after a while (~5 to 10 minutes), it comes back to normal.

As far as I know after a quick test, AC, DC, Diode, and capacity work fine. Probes also are fine.

What kind of problem is this? Maybe a rusty connection or high temps inside my car?

[bob91343]

This is simply a poor connection.  It can be in the switch or the test jacks.  Even a slight corrosion of the test probes can cause it.

That's why a four wire Ohms setup is far superior; it doesn't much care about such things.

[sdancer75]

This is simply a poor connection.  It can be in the switch or the test jacks.  Even a slight corrosion of the test probes can cause it.

That's why a four wire Ohms setup is far superior; it doesn't much care about such things.

That's what I thought. I will open it to check it out.

Thanx