The distinction between a multimeter and a clamp ground resistance tester
The ground resistance clamp meter is also called a clamp ground resistance measuring instrument. Its advantage is that it can measure the magnitude of the current in the line without disconnecting the measured line, no matter what form of ground resistance clamp meter clamp, Generally, only the AC current is measured, and there are also some ground resistance clamp meters specially used to measure DC current. Let me introduce the difference between the clamp ground resistance tester and the multimeter:
In order to ensure the accuracy and safety of the measurement, the following checks should be performed on the grounding resistance clamp meter before use:
1. Appearance inspection: there should be no defects such as damage, especially pay attention to that the jaws should be closed tightly, and the iron core should be free of rust and dirt;
2. If it is a mechanical pointer grounding resistance clamp meter, the pointer should point to "0" at this time, otherwise it should be adjusted to "0";
3. Estimate the magnitude of the measured current and select an appropriate gear. The principle of gear selection is: adjust to the gear that is greater than the measured value and close to it.
When measuring, open the jaws, clamp the wire to be measured into the jaws, close the jaws, and the needle deflects to read the measured current value. Before reading, the grounding resistance clamp meter should be placed as flat as possible (mechanical pointer type) Ground resistance clamp meter), digital ground resistance clamp meter does not matter.
Pay attention when measuring
1. Gloves should be carried during the test (insulated gloves should be clean and dry line gloves), and a guardian should be provided if necessary;
2. When it is necessary to change gears for measurement, the wire should be withdrawn from the jaws first, and then clamped into the wire for measurement after shifting gears;
3. The voltage of the wire under test cannot exceed the voltage level of the grounding resistance clamp meter;
4. It is forbidden to use grounding resistance clamp meter for poor insulation and wire measurement;
5. When measuring, pay attention to keep a safe distance from nearby charged objects, and be careful not to cause phase-to-phase short circuits and phase-to-ground short circuits;
6. It is not suitable to measure line current in a high temperature environment, and it is not suitable to measure near a strong magnetic field. The external magnetic field has a great influence on the measured value. Measure in another place to reduce the error short circuit caused by the magnetic field;
7. It is not suitable for measurement in humid places and thunderstorm weather, because the ground resistance clamp meter must be directly measured by hand, and the operating electrical equipment, the jaws, handles and hands of the measurement personnel of the ground resistance clamp meter must be kept clean and clean. dry;
8. The grounding resistance clamp meter has a large error in measuring non-rated current. The working principle of the grounding resistance clamp meter determines that the grounding resistance clamp meter should be used under the specified rate in addition to measuring sine wave current, and other waveform currents. Errors will occur in the measurement. Generally, the waveform error of the odd harmonic is larger than that of the even spectral wave, especially the 3rd harmonic error becomes larger. Using a grounding resistance clamp meter to measure the half-wave rectified current has a larger error;
9. After use, the gear position should be set to the high current gear. If there is a watch cover, put it into the watch cover, and store it in a dry, dust-free, non-corrosive gas and vibration-free place;
10. High-voltage current cannot be measured, and the voltage of the circuit under test cannot exceed the rated voltage of the grounding resistance clamp meter. The grounding resistance clamp meter cannot measure high-voltage electrical equipment.
The multimeter has the advantages of multi-purpose, wide range, and convenient use. It is a commonly used tool in electrical measurement. It can be used to measure resistance, AC and DC voltage and DC current in electrical maintenance work. Some multimeters can also measure transistors. The main parameters and the capacitance of the capacitor, etc.
