Ground Rod Resistance Measurement

[BOOTY MONSTER]

i was reading this little article over at S-Meter and had a question i figured i would ask here........
how can the impedance of a ground rod be measured ? with a multimeter ??? and where/what would the the probes be connected to ? ground/black probe to ground rod ??? the hot/red probe to .... ???

Ground Rod Resistance Measurement

Ground Rod Resistance Measurement
December 13th Fact-of-the-Day
The resistance between two ground rods spaced farther apart than their length can be measured to obtain a general indication of their likely ability to safely conduct lightning induced currents to earth. However, resistance measurements taken soon after ground rod installation are inaccurate, because the soil is not yet in good contact with the rods. It is necessary to wait six to eight weeks in average soil to obtain a reliable measurement. The measured resistance will be twice the earth contact resistance of one rod if the rods are identical. Earth contact resistance below 5 ohms is excellent. 5 to 10 ohms is good. 10 to 15 ohms is poor. Grounds with more than 15 ohms resistance are of little value in reducing damage from lightning induced currents. ©2004 Martek International All rights reserved.

 

[RatsoW8]

On a related note. the FCC ground conductivity maps for the USA.

M3 Map of Effective Ground Conductivity in the United States (A Wall Sized Map), for AM Broadcast Stations | FCC.gov

 

[Wire Weasel]

The rod itself has no impedance. Impedance is a function of AC resistance. What you would be checking is DC Resistance. Checking the effectiveness of a ground rod in the ground to determine whether or not it's doing any good is done using a a high-voltage Megommeter. You see them in hand-crank models or AC models that run off of 115v, The hand crank ones are the most common. They are also referred to as "Meggers"

Here is a common example. The Biddle brand ones are good.
http://rover.ebay.com/rover/1/711-5...0001&campid=5336136228&icep_item=251165812411