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Low Resistance meters? #137786
07/30/03 01:46 PM
07/30/03 01:46 PM
V
VOLTS  Offline OP
Member
Joined: Jun 2001
Posts: 21
Does anyone have experiance with low resistanec meters? The insurance company said we need to check our grounding connections (Chemical Plant)with a low res meter. We have been using a mulitmeter but they are dictating the meter go to micro-ohms. Any advise on brands or features I should look for?

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Re: Low Resistance meters? #137787
07/30/03 04:07 PM
07/30/03 04:07 PM
B
Bjarney  Offline
Moderator
Joined: Apr 2002
Posts: 2,527
West-Southern Inner-Northeast ...
They may be referring to an ohmmeter that is intended to be used with Kelvin probes/leads—or 4-wire resistance measurements. {Likely the “insurance company” has no clue whatsoever of the instrument needed.}

One is AEMC model 5600.

Re: Low Resistance meters? #137788
07/30/03 04:59 PM
07/30/03 04:59 PM
P
pauluk  Offline
Member
Joined: Aug 2001
Posts: 7,520
Norfolk, England
VOLTS,
Did you intend this post for the non-U.S. area, or were you aiming for general for wider readership? Say the word and I'll transfer the thread if you wish. [Linked Image]

The 4-wire ohmmeter principle goes back many, many years, but it's still a reliable method for measureing very low resistance values. You basically use two wires to pass a reasonable current through the equipment under test and use the second pair of leads to measure the voltage drop and thus calculate the resistance.

Of course, if you have a suitable source of current and voltmeter you can set-up your own ad hoc instrument in the same way.

Re: Low Resistance meters? #137789
07/30/03 07:50 PM
07/30/03 07:50 PM
Bill Addiss  Offline
Member
Joined: Oct 2000
Posts: 3,890
NY, USA
VOLTS,

Here is an Extech brand 4-wire MilliOhm Meter

Re: Low Resistance meters? #137790
07/31/03 09:46 AM
07/31/03 09:46 AM
B
Bjarney  Offline
Moderator
Joined: Apr 2002
Posts: 2,527
West-Southern Inner-Northeast ...
VOLTS — If your measurements need to be in the microohm range, a 10-100 ampere test current is not uncommon. If you don’t need battery portability, and can do some experimenting, something like a Sorensen 10-volt, 100-amp DC constant-current power supply will let you test connections with the millivolt scale of a multimeter—id est, 10mV/100A = 100 μΩ


[This message has been edited by Bjarney (edited 07-31-2003).]

Re: Low Resistance meters? #137791
07/31/03 09:58 AM
07/31/03 09:58 AM
V
VOLTS  Offline OP
Member
Joined: Jun 2001
Posts: 21
No, I did not intend to post in the non-us area sorry for the mistake. Thanks to all for the information.


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