I think the test is called a Null Balace Test, although i don't know how far to put the spikes apart. Also if in tarmac/pavement i can't just drive in spikes.
2006-11-15 08:15:05 · 1 answers · asked by marslarky 2 in Science & Mathematics ➔ Engineering
A Null Balance Test is a test carried out to check either soil resistivity or an earthing (grounding) rod.
The test is call the "Fall of Potential Method" and is carried out by either driving a rod into the earth at the point where you want to measure the earth resistivity and connecting a lead to an instrument (dc generator) and driving two more rods at a suitable distance, normally not less than 30 meters from the rod being tested, with another rod driven at the same distance and in the same line as the other two. All three rods are connected to the dc generator, better known as a type bridge megger.
Let us call the 3 rods A, B & C.
A dc voltage/current is passed between rods B & C, current is measured by adjusting the dials (putting in or taking out resistancae values inside the bridge megger). As the current flowing is proportional to voltage (Ohm's Law), the test is called the "Fall of Potential Method" for measuring resistance......
I hope this is of help...... I guess my answer is a little long winded but hopefully makes sense.
Sourse: Electrical engineer (ret.) with 45+ years experience
2006-11-16 00:25:27 · answer #1 · answered by Bazza66 3 · 0⤊ 0⤋