Introduction to the use and detection of clamp ammeter
Usually when measuring current with an ordinary ammeter, the circuit needs to be cut off and shut down before the ammeter can be connected for measurement. This is very troublesome, and sometimes a normally operating motor 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. Here's how it works:
The clamp ammeter is composed 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 open gap of the iron core without cutting it, and the iron core is closed when the wrench is released. The conductor of the circuit under test passing through the iron core becomes the primary coil of the current transformer, in which current is induced in the secondary coil. As a result, the ammeter connected to the secondary coil will have an indication to measure the current of the circuit under test. The clamp meter can be changed to different measuring ranges by turning the switch. However, it is not allowed to operate with power on when shifting gears. Clamp meters generally have low accuracy, usually level 2.5 to level 5. For ease of use, the meter also has switches of different ranges to provide the functions of measuring current and voltage at different levels.
Instructions
When using a clamp ammeter to detect current, be sure to clamp one conductor (wire) being measured. If you clamp two (parallel wires), the current cannot be detected. In addition, when using the center (core) of the clamp ammeter to detect, the detection error is small .When checking the power consumption of home appliances, it is more convenient to use a line separator. Some line separators 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, a negative number is displayed. This function can be used to detect whether the car's battery is in a charged or discharged state.
Detection of true effective value (RMS)
The average value method clamp ammeter detects the average value of the sine wave through AC detection, and displays the value after amplification 1.11 times (sine wave AC) as a valid value. Waveforms other than sine waves and skew waves with different waveform rates can also be detected. It is also displayed after being magnified 1.11 times, so there will be an indication error. Therefore, when detecting waveforms other than sine waves and distorted waves, please choose a clamp ammeter that can directly test the true effective value.
Leakage detection
Leakage detection is different from ordinary current detection. Two (single-phase 2-wire type) or three (single-phase 3-wire type, three-phase 3-wire type) must be clamped. The ground wire can also be clamped for detection. The insulation management method for detecting leakage current on low-voltage circuits has become the primary means of judgment. Since its confirmation (revision of technical standards for electrical equipment in 1997), it has been used in buildings and buildings that cannot be powered off. Factories gradually use leakage current clamp meters to detect leakage current.
