Ground Resistance reading

[brynm 10+ year member]

Make sure you subtract the resistance from whatever you are using to get to the batt negative as well, I can't imagine it would be that much but...

 

[chrisw91 10+ year member]

is it hooked up to your amp already? if so make sure your ignition is off. if power is flowing through it then that would make a difference.

 

[basscort2009 5,000+ posts]

my cheap dmm would read stupid numbers like that but borrowed a buddys fluke meter and they all zeroed out on his. perfect grounds FTW. get a good meter or you will be guessing. hence this thread.

 

[VisceralSound 10+ year member]

Make sure you subtract the resistance from whatever you are using to get to the batt negative as well, I can't imagine it would be that much but...

I read I was supposed to touch both leads then subtract that from my reading but I didn't get a stable reading from both leads, so what do you mean by the resistances I'm using to get the battery negative exactly?

is it hooked up to your amp already? if so make sure your ignition is off. if power is flowing through it then that would make a difference.

Yes its hooked up to the amp, but the ignition was OFF when tested.

 

---------- Post added at 07:53 PM ---------- Previous post was at 07:52 PM ----------

 

my cheap dmm would read stupid numbers like that but borrowed a buddys fluke meter and they all zeroed out on his. perfect grounds FTW. get a good meter or you will be guessing. hence this thread.

What price range is considered a good meter?

 

[basscort2009 5,000+ posts]

fluke meters are like 50-100 bucks i believe.

 

[brynm 10+ year member]

I read I was supposed to touch both leads then subtract that from my reading but I didn't get a stable reading from both leads, so what do you mean by the resistances I'm using to get the battery negative exactly?

I read your OP that you were using another piece of wire to go to the negative battery terminal, subtract the resistance of any wire that is not a normal part of the circuit.

 

[VisceralSound 10+ year member]

I read your OP that you were using another piece of wire to go to the negative battery terminal, subtract the resistance of any wire that is not a normal part of the circuit.

Oh makes sense, how do I figure the resistance of the wire? I just used some extra Cadence speaker wire I had laying around.

 

[brynm 10+ year member]

Just measure it, that will give you your total added resistance that isn't normally there. You're grounds are still likely high, but you may drop several ohms depending on the size of wire you used.

 

[All_Logix 10+ year member]

I don't know wire generally doesnt have much of a resistance unless you run AC through it. I could be wrong but if you are truely getting 22.4 ohms, I dont think the other components are adding that much more resistance. But I would measure anyway just to be sure. If all else fails, I ran my ground back to the engine block, this works great

 

[VisceralSound 10+ year member]

I don't know wire generally doesnt have much of a resistance unless you run AC through it. I could be wrong but if you are truely getting 22.4 ohms, I dont think the other components are adding that much more resistance. But I would measure anyway just to be sure. If all else fails, I ran my ground back to the engine block, this works great

Well I can do that, or I could just ground it directly to the battery ground correct?

 

[keep_hope_alive Premium Member]

Did you say you have washers between the ring terminal and metal? Don't. Any washers are on the outside between screw head and terminals. Terminal should be touching metal directly.

Bolts are superior to screws for grounding, IMO

When I measure grounds, I use a resistor in series with my test lead. Some DMM's are inaccurate at low resistances. 10 ohm resistor would suffice. Measure lead/resistor first, then measure ground path with lead, then subtract for difference.

Note also that how well the DMM leads are touching will affect results. Oil from your hands can increase meter lead resistance. Clean the leads.

 

[CAT MAN 5,000+ posts]

so i gotta ask so it can be clarified by someone what is the difference in power gain from good to bad ground by 1-4 ohm

 

[VisceralSound 10+ year member]

[quote name='keep_hope_alive']Did you say you have washers between the ring terminal and metal? Don't. Any washers are on the outside between screw head and terminals. Terminal should be touching metal directly.

Bolts are superior to screws for grounding, IMO

When I measure grounds, I use a resistor in series with my test lead. Some DMM's are inaccurate at low resistances. 10 ohm resistor would suffice. Measure lead/resistor first, then measure ground path with lead, then subtract for difference.

Note also that how well the DMM leads are touching will affect results. Oil from your hands can increase meter lead resistance. Clean the leads.[/QUOTE]
1. yes I do have washers between the terminal and metal, I'll remove them tomorrow.
2. I figured so but I just haven't bothered since I had the screws, I think if I use bolts I'd rather do it to frame
3. I touched the leads together and got some funky reading (wasn't stable) I never knew that about oil from hands I'll clean them and try again, thanks @keep_hope_alive

 

[keep_hope_alive Premium Member]

of course, a quality meter is required. you can get an affordable meter of decent quality from MCM Electronics. Tenma is a nice budget brand. They even have a clamp meter that measures DC current for $60 or so.

 

[VisceralSound 10+ year member]

of course, a quality meter is required. you can get an affordable meter of decent quality from MCM Electronics. Tenma is a nice budget brand. They even have a clamp meter that measures DC current for $60 or so.

Either of these as a DMM would work?

Tenma 2,000 Count 3-1/2 Digit Multimeter DMM | 72-7720 (727720) | Tenma

Tenma 4,000 Count 3-3/4 Digit Multimeter DMM w/RS-232 | 72-7735 (727735) | Tenma