The difference between a clamp-on earth 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.
8. 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.
2. Test the inverter circuit by connecting the red meter rod to the P terminal, and the black meter rod to U, V, and W respectively. There should be a resistance value of tens of ohms, and the resistance values of each phase should be basically the same. The reverse phase should be infinite. Connect the black meter rod to the N-end and repeat the above steps to obtain the same result. Otherwise, it can be determined that the inverter module is faulty. Secondly, dynamic testing can only be carried out after the static test results are normal, that is, power on testing. Before and after powering on, the following points must be noted:
1. Before powering on, it is necessary to confirm whether there is an error in the input voltage. Connecting a 380V power supply to a 220V level frequency converter may cause the machine to explode (such as capacitors, varistors, modules, etc.).
2. Check if the various broadcast ports of the frequency converter are properly connected and if there is any looseness in the connection. Abnormal connection may sometimes cause the frequency converter to malfunction, and in severe cases, it may cause the machine to explode.
3. After powering on, check the fault display content and preliminarily determine the fault and its cause.
4. If no fault is displayed, first check if there are any abnormalities in the parameters, reset the parameters, start the frequency converter under no-load (without connecting the motor), and test the three-phase output voltage values of U, V, and W. If there is a lack of phase, three-phase imbalance, etc., the module or driver board may have a fault
5. Under normal output voltage (no phase loss, three-phase balance), conduct load testing. When testing, it is best to conduct a full load test.
