The difference between multimeter and 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 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. In particular, pay attention that the jaws should be tightly closed. The iron core part should be free from 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" bit.
3. Estimate the magnitude of the measured current and select an appropriate gear. The principle of gear selection is: adjust to be greater than the measured value. And it's in the same block as the one that's close.
Open the jaws when measuring. Clamp the wire to be measured into the jaws, close the jaws, and the hands of the meter will deflect. The measured current value can be read out. Before reading, the ground resistance clamp meter should be placed as flat as possible (mechanical pointer ground resistance clamp meter). A digital ground resistance clamp meter doesn't matter.
Pay attention when measuring
1. Gloves should be worn during the test (insulated gloves or clean and dry wire gloves). A guardian should be appointed when necessary.
2. When changing gears for measurement, the wire should be withdrawn from the jaws first. Then clamp into the wire measurement after shifting gears.
3. The voltage of the wire under test. Do not exceed the voltage rating of the ground resistance clamp meter.
4. It is forbidden to use a grounding resistance clamp meter to measure poor insulation and wires.
5. When measuring, pay attention to keep a safe distance from nearby charged objects. And care should be taken not to cause phase-to-phase short circuits and phase-to-ground short circuits.
6. High temperature environment is not suitable for measuring line current. It is not suitable to measure near a strong magnetic field. The external magnetic field has a great influence on the measured value. The grounding resistance clamp meter should not be measured next to high-load current equipment such as bus bars, large-capacity motors, and transformers. It should be measured in another place to reduce the error short circuit caused by the magnetic field.
7. It is not suitable to measure in humid places and thunderstorm weather, because the grounding resistance clamp meter must be directly measured by hand, and the electrical equipment in operation. The jaws and handles of the ground resistance clamp meter and the hands of the measuring personnel 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 the grounding resistance clamp meter determines that the grounding resistance clamping meter should be used under the specified rate. In addition to measuring the sine wave current, the measurement of other waveform currents will produce errors. Generally, odd harmonics are more than even spectral waves. The waveform error is large. In particular, the third harmonic error becomes larger, and the error is also larger when measuring the half-wave rectified current with a grounding resistance clamp meter.
9. After use, the gear should be set to the high current gear, and if there is a watch cover, put it into the watch cover. Store in a place that is dry, dust-free, free from corrosive gases and free from vibration.
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. Ground resistance clamp meters 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.
Common multimeters include pointer multimeters and digital multimeters. Pointer multimeters are multi-functional measuring instruments with the meter head as the core component, and the measured value is read by the pointer of the meter head. The measured value of the digital multimeter is directly displayed in the form of numbers by the LCD screen. It is easy to read, and some also have a voice prompt function.
