Use and detection of clamp Ammeter
Usually, when measuring the current with an ordinary Ammeter, the Ammeter can be connected for measurement only after the circuit is cut off and shut down, which is very troublesome, and sometimes it is not allowed to do so for a normal running motor. At this time, it is much more convenient to use the clamp Ammeter, which can measure the current without cutting off the circuit. The working principle is as follows:
Clamp Ammeter is composed of current transformer and Ammeter. The iron core of the current transformer can be opened when the wrench is tightened; The wire through which the measured current passes can pass through the open gap of the iron core without cutting it off. When the wrench is released, the iron core closes. The tested circuit wire passing through the iron core becomes the primary coil of the current transformer, where the current is induced in the secondary coil through the current. Thus, the Ammeter connected with the secondary coil will have an indication ----- measuring the current of the line under test. The clamp meter can be changed to different ranges by shifting the gears of the switch. However, it is not allowed to operate with power when shifting gears. The accuracy of clamp shaped watches is generally not high, usually ranging from 2.5 to 5 levels. For ease of use, there are also conversion switches with different ranges in the meter for measuring different levels of current and voltage.
Usage method
When using a clamp Ammeter to detect the current, it is necessary to clamp one of the tested wires (wires). If two (parallel wires) are clamped, the current cannot be detected. In addition, when using the clamp Ammeter center (iron core) for detection, the detection error is small. When checking the power consumption of household appliances, it is convenient to use a line separator. Some line separators can amplify the detection current by 10 times, Therefore, the current below 1A can be amplified before detection. When DC clamp Ammeter is used to detect DC current (DCA), if the current flow direction is opposite, it will display a negative number. This function can be used to detect whether the vehicle battery is in charge or discharge state
Detection of true effective value (RMS)
Clamp Ammeter in average mode detects the average value of sine wave through AC detection, and displays the value after 1.11 times amplification (sine wave AC) as a value. Waveforms and skew waves other than sine waves with different waveform rates are also displayed after 1.11 times amplification, which will produce indication errors. Therefore, when detecting waveforms and skew waves other than sine waves, please select clamp Ammeter that can directly test the true RMS
Leakage detection
Leakage detection is different from normal current detection, where two (single-phase 2-wire type) or three (single-phase 3-wire type, three-phase 3-wire type) need to be clamped together. The grounding wire can also be clamped for detection. The insulation management method of detecting leakage current on low-voltage circuits has become the primary means of judgment. Since it was confirmed (the revision of the technical standard of electrical equipment in 1997), leakage current clamp has gradually been used for detection in buildings and factories that cannot power off
