Use and detection of clamp ammeter
Usually, when measuring the current with an ordinary ammeter, it is necessary to cut off the circuit and shut down the circuit before connecting the ammeter for measurement. This is very troublesome, and sometimes the motor in normal operation does not allow this. At this time, it is much more convenient to use a clamp ammeter, which can measure the current without cutting off the circuit. It works as follows:
A clamp ammeter is a combination of a current transformer and an 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 gap opened by the iron core without being cut off, and the iron core is closed when the wrench is released. The measured circuit wire passing through the iron core becomes the primary coil of the current transformer, and the current is induced in the secondary coil by passing the current. So that the ammeter connected to the secondary coil has an indication ----- measure the current of the line under test. The clamp meter can be changed to different ranges by changing the gear of the switch. But it is not allowed to operate with electricity when shifting gears. The clamp meter is generally not high in accuracy, usually 2.5 to 5 grades. For the convenience of use, there are switches of different ranges in the meter for the function of measuring different levels of current and measuring voltage.
Instructions
When using a clamp ammeter to detect current, be sure to clamp one of the measured wires (wires). If two (parallel wires) are clamped, the current cannot be detected. In addition, when using the clamp ammeter center (core) for detection, the detection error is small .When checking the power consumption of home appliances, it is more convenient to use a line splitter. Some line splitters can amplify the detection current by 10 times, so the current below 1A can be amplified before detection. Use a DC clamp ammeter to detect the DC current (DCA), if the current flows in the opposite direction, it will display a negative number. This function can be used to detect whether the car's battery is in a charging state or a discharging state.
True effective value (RMS) detection
The clamp ammeter of the average value method detects the average value of the sine wave through AC detection, and displays the value after the magnification of 1.11 times (sine wave AC) as a value. It is also displayed after being enlarged by 1.11 times, so there will be an indication error. Therefore, when detecting waveforms other than sine waves and crooked waves, please choose a clamp-on ammeter that can directly test the true RMS value.
Leakage detection
Leakage detection is different from the usual current detection, two (single-phase 2-wire type) or three (single-phase 3-wire type, three-phase 3-wire type) must be clamped. It can also clamp the grounding wire 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 (revision of electrical equipment technical standards in 1997), it has been used in buildings and The factory gradually adopts the leakage current clamp meter to detect.
