By hvhipot 
For electricians, they often use a clamp-on ground resistance tester to measure ground resistance. When measuring a grounding system with loops, the clamp-on ground resistance meter does not need to disconnect the ground lead wire or auxiliary electrodes. It is safe, fast, and easy to use. The clamp ground resistance meter can measure ground faults that cannot be measured by traditional methods, and can be applied to occasions that cannot be measured by traditional methods, because the clamp ground resistance meter measures the combined value of the grounding body resistance and the ground lead resistance. So for the special needs on site, the maximum measurement range is needed, so how to use the clamp ground resistance tester to measure the maximum range?
Working principle of clamp ground resistance tester
① Principle of resistance measurement
The basic principle of the clamp ground resistance meter to measure the ground resistance is to measure the loop resistance. The jaw part of the clamp meter is composed of a voltage coil and a current coil. The voltage coil provides an excitation signal and induces an electric potential E on the circuit under test. Under the action of the electric potential E, a current I will be generated in the circuit under test. The clamp meter measures E and I, and the measured resistance R can be obtained through the following formula.
②Principle of current measurement
The basic principle of the clamp ground resistance meter to measure current is the same as that of the current transformer. The AC current I of the wire to be measured generates an induced current I1 through the current magnetic ring and current coil of the clamp. The clamp meter measures I1, and the measured current I can be obtained by the following formula.
2. Parameter characteristics of clamp-on ground resistance tester
①Wide measuring range and high resolution: measuring range from 0.01Ω～1000Ω, resolution 0.01Ω, grounding resistance below 0.7Ω can also be accurately measured
②Large-capacity data storage: 200 sets of measurement data can be stored.
③Measurement range of ground resistance:
Double clamp method: 0.01Ω～1000Ω
Ground pile method: 0.01Ω～1000Ω
3. Correct use method of clamp ground resistance tester
①Squeeze the trigger once or twice before starting the machine to ensure that the jaws are well closed
②Press the POWER button to enter the power-on state. First, the LCD will be automatically tested, and all its symbols will be displayed. Then start the self-test. During the self-test, “CAL6, AL5, CAL4”, “CALO, OW” are displayed in sequence. When “HV Hipot Electric Co., Ltd.” appears, the self-test is completed and the resistance measurement mode is automatically entered.
③During the self-inspection process, do not press the trigger, open the jaws, or clamp any wires. It is reminded to keep the clamp meter in its natural static state, and not to turn the clamp meter over, and not to apply external force to the jaws, otherwise the accuracy of the measurement cannot be guaranteed.
④When the self-inspection is completed, it displays “01-n” and it also flashes.))) symbol.
The key to how to use the clamp-on ground resistance tester to measure the maximum range is to be familiar with the working principle of ground resistance. With the memorization of the parameters, you can adjust and measure the measurement results you want when you use it.