"Roy Lewallen" wrote in message
...
Please ignore my earlier posting. I saw NEC and thought the reference
was to the program of that name (Numerical Electromagnetics Code). The
other responses caused me to re-read your posting more carefully and I
see you're referring instead to the National Electrical Code. 60 Hz
measurement is of course what you want to do, and my response was
entirely inappropriate in that context.

Whew, thanks, Roy, I thought you'd finally "lost" it! (hi hi and grin)
I wish I had something more solid to contribute, but I do remember my
USAF days when the aircraft parking ramp static grounding rings required a
scheduled resistance inspection, the date stenciled in black on yellow
circle. The resistance had to be below 10,000 ohms. The instrument the civil
engineers used to make the measurements was hand cranked, something like the
"Megger" used for insulation break-down testing. I cannot say whether it was
a regular "megger" or a specialized instrument.
Anyhow, we mechanics tried to do our own testing with an ordinary VOM
and found the task quite vexing. One problem was that stray currents in the
ground drove the ohmmeter crazy, and as if that wasn't enough, the ohmmeter
probes current caused an electrolytic (?) reaction, sort of like trying to
measure the resistance of a battery using a standard VOM.
Now I'm going to back up and read some of the references provided by
previous responders.
Old Chief Lynn, W7LTQ (I still like Furuno, Roy!)