1. Disconnect the connection point between the grounding trunk line and the grounding body, or disconnect the connection points of all grounding branch lines on the grounding trunk line.
2. Insert two grounding rods into the ground 400mm deep, one is 40m away from the grounding body, and the other is 20m away from the grounding body.
3. Place the megger on a flat place near the grounding body, and then perform wiring.
(1) Use a connecting wire to connect the terminal E on the meter and the grounding body E' of the grounding device.
(2) Use a connecting wire to connect the terminal pile C on the meter and the grounding rod C' which is 40m away from the grounding body.
(3) Use a connection wire to connect the terminal pile P on the meter and the grounding rod P' which is 20m away from the grounding body.
4. According to the grounding resistance requirements of the measured grounding body, adjust the coarse adjustment knob (there are three adjustable ranges on it).
5. Shake the watch evenly at a speed of about 120 rpm. As the hands deflect, adjust the fine-tuning dial until the hands are centered. The reading set by the fine-tuning dial is multiplied by the coarse-adjustment positioning multiple, which is the grounding resistance of the grounding body under test. For example, the reading of the fine adjustment is 0.6, and the resistance positioning multiple of the coarse adjustment is 10, then the measured grounding resistance is 6Ω.
6. In order to ensure the reliability of the measured grounding resistance value, the orientation should be changed and retested again. Take the average value of several measured values as the grounding resistance of the grounding body.