Do you know how to measure the earth resistance? if so
explain it
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Answer Posted / felix shapilo
Ohmmeter measurements are normally made with just a two-
point measurement method.
However, when measuring very low values of ohms, in the
milli- or micro-ohm range, the two-point method is
not satisfactory because test lead resistance becomes a
significant factor.
A similar problem occurs when making ground mat resistance
tests, because long lead lengths of up to 1000
feet, are used. Here also, the lead resistance, due to long
lead length, will affect the measurement results.
The four-point resistance measurement method eliminates
lead resistance. Instruments based on the four-point
measurement work on the following principle:
· Two current leads, C1 and C2, comprise a two-wire
current source that circulates current through the
resistance
under test.
· Two potential leads, P1 and P2, provide a two-wire
voltage measurement circuit that measures the voltage
drop across the resistance under test.
· The instrument computes the value of resistance from the
measured values of current and voltage
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