Operation; Ground Resistance Measurement Procedure (3-Point); 2-Point Measurement (Simplified Measurement) - AEMC 4620 User Manual

Ground testers

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3.1 GROUND RESISTANCE MEASUREMENT PROCEDURE

(3-POINT)

Ground

Strip

Ground Rod

WARNING: Use extreme caution when disconnecting the ground

connection from the rest of the circuit. Current may be flowing and a

dangerous potential could exist between the disconnected wires.

■ X and Xv (E, ES) are shorted.

■ Disconnect shorting link between Y and Z (S, H).

■ Connect X to the ground rod to be tested.

■ Connect Y (S) to the center electrode.

■ Connect Z (H) to the outer electrode.

■ Depress the "Test" button to measure ground resistance.

3.2 2-POINT MEASUREMENT

This is an alternative method to 3-Point measurement when an excellent ground

is already available.

In congested areas without room to drive the two auxiliary ground electrodes, the

2-Point measurement method may be applied. Since the two auxiliary ground

rods are not used, the reading will show two grounds in series. Therefore, the

water pipe or other ground must be very low in resistance so that it will be

negligible in the final measurement. The lead resistances will also be measured

and should be deducted from the final measurement.

3. OPERATION

Ω

Alligator Clips

Figure 15

(SIMPLIFIED MEASUREMENT)

Digital Ground Resistance Tester Models 4620 & 4630

Y Electrode

Z Electrode

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4630