The difference between clamp grounding resistance tester and multimeter
The grounding resistance clamp type meter, also known as a clamp type grounding resistance measuring instrument, has the advantage of being able to measure the current in the circuit without disconnecting the measured circuit. Regardless of the form of grounding resistance clamp type meter, it generally only measures the AC current of the workpiece, and there are also some grounding resistance clamp type meters specifically used to measure DC current. Let me introduce the difference between a clamp type grounding resistance tester and a multimeter:
To ensure the accuracy and safety of 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 should be free of rust and dirt.
If it is a mechanical pointer type grounding resistance clamp meter, the pointer should refer to "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 also in the close 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 gauge should be as flat as possible (mechanical pointer type grounding resistance clamp gauge). The digital grounding resistance clamp meter doesn't matter.
Pay attention when measuring
1. Gloves should be worn during testing (insulated gloves should be replaced with 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 grounding resistance clamp meter cannot be exceeded.
4. It is prohibited to use a grounding resistance clamp meter to measure poor insulation and wires.
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 line 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 measured values. Ground 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 at a different location to reduce error short circuits caused by magnetic fields.
7. Measurement should not be carried out in damp places 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 grounding resistance clamp meter must be kept clean and dry during measurement.
8. The grounding resistance clamp meter has a large error in measuring non rated current. The working principle of a grounding resistance clamp meter determines that it is necessary to use a grounding resistance clamp meter at a specified rating rate. In addition to measuring sine wave currents, measuring other waveform currents will result in errors. Generally, the waveform error of odd harmonic waves is greater than that of even spectral waves. Especially when the third harmonic error increases, using a ground resistance clamp meter to measure the half wave rectification current also results in significant errors.
9. After use, the gear should be placed in 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 grounding resistance clamp meter. The grounding resistance clamp meter cannot measure high voltage
