Condition: There must be a known good earth, such as PEN, etc. The measured result is the sum of the resistance of the tested earth and the known earth. If the known earth is much smaller than the resistance of the tested earth, the measurement result can be used as the result of the tested earth.
Applicable to: Areas with dense buildings or sealed concrete floors where ground rods cannot be driven.
Wiring: Connect E+ES to the tested earth, and H+S to the known earth.
2. Three-Point Method
Condition: Two ground rods are required: an auxiliary earth and a detection electrode. The distance between each ground electrode should not be less than 20 meters.
The principle is to apply current between the auxiliary earth and the tested earth, measure the voltage drop between the tested earth and the detection electrode. The measurement result includes the resistance of the measuring cable itself.
Applicable to: Foundation grounding, construction site grounding, and lightning protection spherical lightning rod QPZ grounding.
Wiring: Connect S to the detection electrode, H to the auxiliary earth, and connect E and ES together to the tested earth.
3. Four-Point Method
Basically the same as the three-point method, used to replace the three-point method in low ground resistance measurements and to eliminate the influence of measuring cable resistance on measurement results. During measurement, E and ES must be separately and directly connected to the tested earth. This method has the highest accuracy among all ground resistance measurement methods.
4. Single-Clamp Measurement
Condition: Measure the ground resistance of each grounding point in a multi-point grounding system, and the grounding connection cannot be disconnected to prevent danger.
Applicable to: Multi-point grounding, where connections cannot be disconnected, to measure the resistance of each grounding point.
Wiring: Use a current clamp to monitor the current at the tested grounding point.
5. Dual-Clamp Method
Condition: Multi-point grounding, without driving auxiliary ground rods, to measure a single ground.
Wiring: Use the current clamp specified by the manufacturer and connect it to the corresponding socket. Clamp both clamps onto the grounding conductor, with a distance greater than 0.25 meters between the two clamps.
Ground Resistance Tester Product Recommendations
