Stakeless Earth Ground Clamp Meters

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garnerm

Member
Location
Montgomery, AL
How effictive are these and are they worth the money? I cannot get my head around how this can tell you the earth to ground resistance without actually touching the ground. Also, what are the standard values you should be reading at the service entrance grounding electode and say a few branch panels downstream? How much should the resistance go up typically?
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
Those are only used on a grounding electrode or grounding electrode conductor. They have no use at a down stream panel that has an EGC.
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
121102-1056 EDT

An assumption exists that the measurement is being made in a system with a multi-point grounded neutral from the power company. Thus, the power company at its many neutral grounding points has a low impedance to earth in comparison with the single ground rod or two you are measuring.

A known voltage is induced into the (your ground rod)-(earth)-(many power company ground points) loop and the current from this known induced voltage is measured, from the voltage and current a resistance is calculated, and this value is assumed to approximate your ground rod resistance.

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Gregg Harris

Senior Member
Location
Virginia
Occupation
Electrical,HVAC, Technical Trainer
How effictive are these and are they worth the money? I cannot get my head around how this can tell you the earth to ground resistance without actually touching the ground. Also, what are the standard values you should be reading at the service entrance grounding electode and say a few branch panels downstream? How much should the resistance go up typically?


Take a look at Megger or Flukes websight for some good video discriptions
 
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