checked my ground with dmm today....

[aaron7114 10+ year member]

I checked my ground today with a DMM and it showed -0.02. Is that possible?

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[JimJ 5,000+ posts]

You had the leads "reversed"...doesn't matter.

 

[QuadinExploder 10+ year member]

which lead goes where?

 

[aaron7114 10+ year member]

You had the leads "reversed"...doesn't matter.

Alright so its just 0.02 resistance?

Is that good for the ground?

 

[BassAce 10+ year member]

Just curious, how much is your fuse size?

 

[BassAce 10+ year member]

With a 100 amp going through the ground there will be a 2v voltage drop or about 100w. With 50 amps there will be about a 1v drop or about 50w. I would try to get a little better connection. But I could be wrong.

 

[aaron7114 10+ year member]

With a 100 amp going through the ground there will be a 2v voltage drop or about 100w. With 50 amps there will be about a 1v drop or about 50w. I would try to get a little better connection. But I could be wrong.

The fuse on the power wire going to my amp is 200 amps. But that shouldn't have any effect when testing the ground.

I just put one lead on the negative on the battery and the other lead on my ground spot for my amp.

I got to thinkin about it just now, and I bet there will be a difference in resistance with the car on wont there? I didn't turn it on at all.

 

[Decipha 10+ year member]

aaron my friend, bass wasn't talkin about your fuse, he was talking about a load of 100 amps being pulled thru that ground

 

[n2audio 5,000+ posts]

Alright so its just 0.02 resistance?
Is that good for the ground?

my question is - what exactly did you measure?? Where did you place the probes?

 

[ultimate157 5,000+ posts]

my question is - what exactly did you measure?? Where did you place the probes?

x2.

 

[aaron7114 10+ year member]

my question is - what exactly did you measure?? Where did you place the probes?

One probe on the negative on the battery...the other probe on my ground spot for my amp.

 

[n2audio 5,000+ posts]

First of all - there's no +/- measuring resistance. You can't have (-) ohms.

My guess is the DMM was just confused.

There is more resistance in the DMM leads than there would be in the chassis.

That's why this type of measurement is rarely useful.

The accurate method is to pass a known amount of current through the chassis and measure the voltage drop.