Ground resistance testers usually have the following measurement methods: single clamp method, double clamp method, two-wire method, three-wire method and four-wire method. Each has its own characteristics. In actual measurement, try to choose the correct method to make the measurement. The results are accurate.

1. Single clamp measurement

Measure the grounding resistance of each position in the multi-point grounding, and do not disconnect the grounding connection to prevent danger.

Applicable to: multi-point grounding, not disconnected. Measure the resistance of each connection point.

Wiring: Use a current clamp to monitor. The current at the location being tested.

2. Double clamp method

Condition: Multi-point grounding, no auxiliary grounding stake. Measure the ground.

Wiring: Use the current clamp of the grounding resistance test instrument manufacturer to connect to the corresponding socket. Clamp the two clamps on the grounding conductor, and the distance between the two clamps should be greater than 0.25 meters.

3. Two-line method

Condition: There must be a known good ground. Such as PEN and so on. The measured result is the sum of the resistance of the measured ground and the known ground. If the known ground is much smaller than the resistance of the measured ground, the measurement result can be used as the measured ground result.

Applicable to: buildings and concrete floors, etc. Seal areas where piles cannot be driven.

Wiring: e+es receives the measured ground. h+s receive known ground.

4. Three-line method

Conditions: There must be two ground rods: an auxiliary ground and a detection electrode, and the distance between each ground electrode is not less than 20 meters.

The principle is to add a current between the auxiliary ground and the measured ground. Measure the voltage drop measurement result between the measured ground and the probe electrode. This includes measuring the resistance of the cable itself.

Applicable to: ground grounding, construction site grounding and lightning ball lightning rod, QPZ grounding.

Wiring: s connect to the detection electrode. h then auxiliary ground. After e and es are connected, the measured ground is connected.

5. Four-wire method

It is basically the same three-wire method, which eliminates the influence of the measurement cable resistance on the low ground resistance measurement result when it replaces the three-wire method. When measuring, e and es must be directly connected to the measured ground, which is very accurate in all grounding resistance measurement methods.