How to measure earth resistance for building

[STAR87]

After we finished from making earth network around one of our projects (building 3500 m2) i wanna measure the earth resistance i have read that there r a lot of method to measure this resistance but my question is about
the measure of tingle(delta) which make three rods as triangle equal in every rod long and then starting measure
there is another method
is to put in earth 4 rods one of them already part of earth network and the distance between rods must be equal and the part which in earth must be equal for 4 rods
which method is th best ..what is the proper long for the rods which will be on earth?

 

[brian john]

Having trouble following your questions BUT.

The standard method for an installed grounding electrode system is the 3-point method.

The 4-point method is utilized to determine the resistance of the soil in a particular area and then design an electrode system for that area.

If the electrode (triangle or not) is in service you cannot make an accurate measurement of the electrode.

You would need to isolate the electrode from the service and building to make accurate measurements.

There is a lot of good data on the web regarding ground resistance measurements.

http://www.aemc.com/techinfo/techworkbooks/ground_resistance_testers/950-WKBK-GROUND-WEB.pdf