Ground Testing

  • Thread starter Royherd27
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Main Question or Discussion Point

Can the point to point test, (to determine the resistance between the main grounding system and all the major electrical frames, system neutral, etc) be made with an ordinary multimeter or does it need a special ground test tool?
The NETA value of 0.5 ohm is widely accepted?
 

Answers and Replies

  • #2
meBigGuy
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The advantage of an approved tester is that it is consistent with your country's requirements, and doesn't depend on you interpreting the rules and the readings and correctly applying the correct stimulus.
 
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Can the point to point test, (to determine the resistance between the main grounding system and all the major electrical frames, system neutral, etc) be made with an ordinary multimeter or does it need a special ground test tool?
The NETA value of 0.5 ohm is widely accepted?
The basic problem with ordinary multimeter is that its leads will add resistance in series. You will need long leads if you are probing between major electrical frames, the lead resistance will probably be orders of magnitude more than the bonding resistance you are trying to measure.

You need a 4 wire "Kelvin" resistance meter (previous posters provided links). Here is how they work:

2 leads supply a constant controlled current source through the ground structure under test (lead resistance not an issue here since it is a current source). The other two leads measure voltage across the current source. The voltage measurement leads draw very low leakage current so lead resistance here is not an issue.
 

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