[TowerTalk] Mot R36 related to NUMBER of installed ground rods

[jimlux]

On 11/3/17 7:15 AM, john at kk9a.com wrote:
> How is ground resistance measured?
> 

With an AC ohmmeter specifically designed for this application.  Mostly, 
it's a matter of standard probes, standard measuring voltages and 
currents, etc. so that everyone's measurements are the same.

googling "grounding system resistance testing" turns up lots of links:

http://www.esgroundingsolutions.com/how-to-do-electrical-grounding-system-testing/
http://www.weschler.com/_upload/sitepdfs/techref/gettingdowntoearth.pdf
http://www.aemc.com/techinfo/techworkbooks/ground_resistance_testers/950-WKBK-GROUND-WEB.pdf

there's a difference between measuring soil resistivity and grounding 
system resistance, but the same kinds of measurement tools are used.

I'm sure you could use standard ham DMM and a variac + isolation 
transformer to do something that is functionally similar.

The tricky parts are the standardized electrodes (that's just a matter 
of getting the right length and diameter) and not having your 
measurement perturbed by ground currents from other sources and 
interference.  Kind of like the problems with measuring an 160m antenna 
when there's strong AM stations nearby.







> John KK9A
> 
> To:	towertalk at contesting.com
> Subject:	Re: [TowerTalk] Mot R36 related to NUMBER of installed ground rods
> From:	jimlux <jimlux at earthlink.net>
> Date:	Fri, 3 Nov 2017 05:52:59 -0700
> 
> 
> 
> "The contractor shall install sufficient ground rods in accordance with
> document XYZ that the measured ground resistance is less than 5 ohms."
> 
> At the end of the job, the customer goes out, measures the resistance,
> finds it's 4.2 ohms and says "you get paid"
> 
> 
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