how to measure earth pit resistance

Answer Posted / satya narayan padhy

Earth pit resistance is measured by Earth tester, Earth
tester have four terminals P1,P2,C1,C2 i.e. Two potential &
Two Current terminals. while earth pit testing, P2 & C2 are
shorted and C1 connected to current spike(Conductive rod)
which should be drived into soil at around 30 meter
distance from earth pit and P1 is connected to potential
spike(Conductive rod) drived at around 15 mtr away from
earth pit in the opposite direction of current spikes.By
rotating
the handle of meter(in old meters) or by pressing test
button (in new type meter) one can get earth resistance.Now
Potential spikes are drived at different locations toward
earth pit and current spike side and a curve between
distance and resistance is plotted. Earth resistance will
be platue of the graph.In this meter current is passed
between earth pit and current spike and potential is
measured between potential spike and earth pit. Ratio
between Voltage measured and current passed thrugh the
earth is the resitance of earth pit.

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