Granted I have a cheap DMM. When I short the leads and measure in the lowest resistance scale, I am reading 2.6 ohms. I assume this is the resistance of the leads.

Even in better meters, leads have to have at least some resistance correct? How is that accounted for? Is there a way to zero them? Or do you just need to use leads designed for use of that particular DMM.

 

any meter worth purchasing has a "zero" button

 

Granted I have a cheap DMM. When I short the leads and measure in the lowest resistance scale, I am reading 2.6 ohms. I assume this is the resistance of the leads.

It could also be a flaky connection between a lead wire and the plug or clip/prod on one of its ends.

 

Even in better meters, leads have to have at least some resistance correct? How is that accounted for?

The Fluke I used at work had a Relative Reference function.
You touch the leads together and press that button.
That memorizes the lead resistance value and then subtracts it from subsequent readings.

 

I have an ancient Fluke 8022 that does not appear to be working but does not appear to have a zero function. I am not sure where it sat in their line way back when. I suspect it was low in their line. I used to have one tossed in my field engineer toolkit from a million years ago.

 

There are 4-wire and 5-wire ohm functions. One Fluke meter had a FP Zero knob. Usually, you have to live with <0.5 ohms or so.

Try shorting the inputs with a paper clip. If it's significantly better, you might want to invent in better leads.

 

Every analog meter I ever had had an ohms zero pot. Not all of them had a parallax mirror. I don't think I've ever had a DMM, not even my Fluke, that has an ohms zero adjust. Perhaps it's built in some way and I just don't know it. I could see something where if you turn the range knob with the leads shorted it nulls the measurement automatically. But I don't know if any meter actually has functionality like that.

 

My DMM autozeroes when I switch it on, while at the same time I firmly touch the leads together. Have you tried that?
It's not something written in its manual, but rather something I discovered on my own.

 

Every analog meter I ever had had an ohms zero pot. Not all of them had a parallax mirror. I don't think I've ever had a DMM, not even my Fluke, that has an ohms zero adjust. Perhaps it's built in some way and I just don't know it. I could see something where if you turn the range knob with the leads shorted it nulls the measurement automatically. But I don't know if any meter actually has functionality like that.

Yeah I reason I am asking. I remember from my old analog meter days.

 

My DMM autozeroes when I switch it on, while at the same time I firmly touch the leads together. Have you tried that?
It's not something written in its manual, but rather something I discovered on my own.

Mine doesn't do that. I guess I need to spend a little more than free with purchase to get that feature.

Good news after playing with it I got it down to 1 ohm. I guess I had a bit of corrosion on the lead connectors. A short piece of copper wire yields the same reading so I guess my leads are pretty dsecent.

 

Mine doesn't do that. I guess I need to spend a little more than free with purchase to get that feature.

Good news after playing with it I got it down to 1 ohm. I guess I had a bit of corrosion on the lead connectors. A short piece of copper wire yields the same reading so I guess my leads are pretty dsecent.

Have you opened it? Could you find some sort of adjustment trimpot?

 

Have you opened it? Could you find some sort of adjustment trimpot?

6 of them. No labeling.

 

6 of them. No labeling.

Then... by all means... DON'T MESS WITH THEM!

 

Plan B would be to bypass one pot at a time by connecting an arbitrary resistor between its contacts... see if it affects the zero reading on your DMM... and maybe that would be the right pot to adjust...

 

Get a pencil and paper and subtract the shorted lead resistance value from the resistance of your load.

My oldest Fluke DMM dorm 1983 does not have auto zero either. The pencil and paper method works for me.

 

Yeah I reason I am asking. I remember from my old analog meter days.

Most of the analog meters really needed a manual zero because of the basic method they used to make resistance measurements. DMMs use a different method that use internal references that eliminate the shortcomings of the method used by most analog meters. I think most basic DMMs assume that lead wire resistance is small compared to the resistances typically measured and, if not, then the user will either take separate measurements of the lead resistance to subtract it or will do a four-wire measurement.

 

All the Fluke meters I've owned had this feature, so I assumed it was on all Flukes. I was wrong. Most of the lower tier meters don't have it.

 

Most of the analog meters really needed a manual zero because of the basic method they used to make resistance measurements. DMMs use a different method that use internal references that eliminate the shortcomings of the method used by most analog meters. I think most basic DMMs assume that lead wire resistance is small compared to the resistances typically measured and, if not, then the user will either take separate measurements of the lead resistance to subtract it or will do a four-wire measurement.

Wouldn't one of those things be the temperature of the meter movement?

 

My fluke read zero ohms whenever I shorted the probetips together, but years later it was time to change the test probes and, being cheaper probes they probably have a smaller gauge wire and it measures about 0.7 ohms. I got use to it, after all I don't measure very low value resistors very often.

 

Wouldn't one of those things be the temperature of the meter movement?

Temperature would have some effect, though probably small; mainly, the ZERO adjustment is needed to compensate for changes in battery voltage.