Is a clamp meter better or a multimeter better?
Clamp meters and multimeters have their own advantages and disadvantages according to different places where electricians use them. It is impossible to simply say that they are good or bad. Clamp meters are divided into mechanical pointer clamp meters and digital clamp meters. Its biggest advantage is that it can measure the magnitude of the current in the line without disconnecting the measured line. No matter what kind of clamp meter is clamped, it generally only measures AC current, and there are also some clamp ammeters specially used to measure DC current. The more popular digital clamp meters are shown in the figure below. In order to ensure the accuracy and safety of the measurement, the following checks should be performed on the clamp ammeter 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.
②If it is a mechanical pointer clamp meter, the pointer should point to "0" at this time, otherwise it should be adjusted to "0".
③ Estimate the size 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, deflect the hands, and read the measured current value. Before reading, the clamp ammeter should be placed as flat as possible (mechanical pointer clamp meter), digital clamp meter does not matter.
Matters needing attention in clamp ammeter measurement
① Gloves should be worn during the test (insulated gloves should be clean and dry line gloves), and a guardian should be provided if necessary.
②When shifting gears for measurement, the wire should be withdrawn from the jaws first, and then clamped into the wire for measurement after shifting gears.
③The voltage of the wire under test cannot exceed the voltage level of the clamp meter.
④ It is forbidden to use clamp meter to measure poor insulation and bare wires.
⑤ When measuring, pay attention to keep a safe distance from nearby charged objects, and be careful not to cause phase-to-phase short-circuit and phase-to-ground short-circuit.
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 clamp ammeter should not be measured next to high-load current equipment such as busbars, large-capacity motors, and transformers. It should be measured in another place to reduce the error caused by the magnetic field. short circuit.
⑦ It is not suitable for measurement in humid places and thunderstorms, because the clamp meter must be directly measured by hand, and the operating electrical equipment, the jaws and handles of the clamp ammeter and the hands of the measuring personnel must be kept clean and dry during measurement.
⑧ The clamp ammeter has a large error in measuring non-industrial current. The working principle of the clamp-on ammeter determines that the clamp-on meter should be used under the specified rating. In addition to measuring the sine wave current, there will be errors in the measurement of other waveform currents. Generally, the waveform error of odd-order harmonics is larger than that of even-order spectral waves. , especially the 3rd harmonic error is the largest, and the half-wave rectified current is measured with a clamp ammeter, and the error is also relatively large.
⑨After use, the gear position should be set to the highest current level. 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 clamp ammeter. Clamp meters cannot measure high voltage electrical equipment. The multimeter has the advantages of multi-purpose, wide range, and convenient use. It is the most commonly used tool in electrical measurement. In electrical maintenance work it can be used to measure resistance, AC and DC voltage and DC current. Some multimeters can also measure the main parameters of transistors and the capacitance of capacitors. Mastering the use of multimeters is a basic skill in electrotechnical technology. Common multimeters include pointer multimeters and digital multimeters. The pointer multimeter is a multi-functional measuring instrument with the meter head as the core component, and the measured value is read by the pointer of the meter head.
