The difference between a clamp-type ground resistance tester and a multimeter
The ground resistance clamp meter, also known as a clamp ground resistance measuring instrument, has the advantage of being able to measure the magnitude of the current in the circuit without opening the measured circuit. Regardless of the form of ground resistance clamp meter, it generally only measures the AC current of the workpiece, and there are also some ground resistance clamp meters specifically used to measure DC current. Let me introduce the difference between a clamp type grounding resistance tester and a multimeter:
To ensure accurate and safe measurement, the grounding resistance clamp meter should be checked before use.
1. Appearance inspection: There should be no defects such as damage. Especially note that the jaws should be tightly closed. The iron core part should be rust free and free of dirt.
If it is a mechanical pointer type ground resistance clamp meter, the pointer should indicate "0". Otherwise, it should be adjusted to the "0" position.
3. Estimate the magnitude of the measured current, select an appropriate gear, and the principle of gear selection is to adjust it to be greater than the measured value. And it's also the closest gear.
Open the jaws during measurement. Clamp the measured wire into the jaws, close the jaws, and deflect the watch needle. The measured current value can be read out. Before reading, the position of the grounding resistance clamp meter should be as flat as possible (mechanical pointer type grounding resistance clamp meter). The digital grounding resistance clamp meter doesn't matter.
Attention should be paid during measurement
1. Gloves should be worn during testing (insulated gloves should be clean and dry wire gloves). If necessary, a guardian should be appointed.
When shifting gears for measurement, the wires should be removed from the jaws first. After shifting gears, clamp in the wires for measurement.
3. The voltage of the tested wire. The voltage level of the ground resistance clamp meter cannot be exceeded.
4. Poor insulation and wires are prohibited from being measured using a ground resistance clamp meter.
5. When measuring, pay attention to maintaining a safe distance from nearby charged objects. And attention should be paid not to cause phase to phase short circuits and phase to ground short circuits.
6. It is not suitable to measure circuit current in high temperature environments. It is not suitable to measure near strong magnetic fields, as external magnetic fields have a significant impact on the measurement values. Grounding resistance clamp meters should not be used for measurement near high load current equipment such as busbars, large capacity motors, and transformers. It should be measured in a different location to reduce error short circuits caused by magnetic fields.
7. Measurement should not be carried out in damp areas or thunderstorm weather, as the grounding resistance clamp meter must be held by hand for direct measurement of electrical equipment in operation. The jaws, handles, and hands of the measuring personnel of the grounding resistance clamp meter must be kept clean and dry during measurement.
The ground resistance clamp meter has a large error in measuring non rated current. The working principle of a ground resistance clamp meter determines that it is necessary to use a ground resistance clamp meter at the specified rated rate. In addition to measuring sine wave currents, measuring other waveform currents will result in errors. Generally, odd harmonic waves have larger waveform errors than even spectral waves. Especially when the error of the third harmonic becomes larger, using a ground resistance clamp meter to measure the half wave rectification current also results in a larger error.
9. After use, the gear should be set to the high current gear, and if there is a watch cover, it should be placed in the watch cover. Store in a dry, dust-free, non corrosive gas, and vibration free place.
10. High voltage current cannot be measured, and the voltage of the tested circuit cannot exceed the rated voltage of the ground resistance clamp meter. The grounding resistance clamp meter cannot measure high-voltage electrical equipment.
