Using 2 ground rods as a substitute for a H2O ground

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Re: Using 2 ground rods as a substitute for a H2O ground

Someone tell this ignoramus please: What is unique about testing the resistance of a ground rod? Seems you could do it with an Ohmmeter, but that would be too easy. I have met a PE whose specialty was ground rod testing and design. Did not watch him at work though.
 
Re: Using 2 ground rods as a substitute for a H2O ground

rattus wrote:
Seems you could do it with an Ohmmeter
Click to expand...
What would be the best way? Unhook the GEC and measure resistance between the GEC and the grounding electrode(s)? :eek:

......Mike
 
Re: Using 2 ground rods as a substitute for a H2O ground

rattus and woofy
There are test sets to measure ground resistance. They use different methods including the fall of potential method and others. I got info from an IEEE paper. It is not nearly as simple as measuring resistance with an ohmmeter. The test sets generate voltages and currents that aren't related to 60 hz, and use that to measure the resistance. If you use a simple ohm meter, you won't get an accurate measurement.
Jim T
 
Re: Using 2 ground rods as a substitute for a H2O ground

Jtester, I knew in my heart it would not be simple. Perhaps it is like the 4-point resistivity test they use on silicon wafers. Four probes are arranged in a row. Current is forced through the outer two; then voltage is measured across the inner two. Then sheet resistivity and/or bulk resistivity is computed from the readings. Maybe I should learn how to measure earth grounds so I could call myself an expert.
 
Re: Using 2 ground rods as a substitute for a H2O ground

Jim-

Sorry about that I was bein a Smarta**. Unhooking a GEC is a good way to get a nasty surprise. I should leave the humor to the pro's.

My apologies.......Mike
 
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