How does a clamp ammeter measure DC current?
How to measure DC current with clamp ammeter is divided into three methods, which are line separation, true RMS detection and leakage detection.
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.
1. Line separation
When using a clamp ammeter to detect current, be sure to clamp a measured wire (wire). 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. When detecting DC current (DCA) with a DC clamp ammeter, if the current flows in the opposite direction, it will display a negative number. This function can be used to detect whether the battery of the car is in a charging state or a discharging state.
2. True effective value detection
Another method is that the clamp ammeter in the average value mode detects the average value of the sine wave through AC detection, and displays the value after amplifying 1.11 times (sine wave AC) as an effective value. Waveforms other than sine waves and distorted waves with different waveform ratios are also enlarged by a factor of 1.11 and displayed, so indication errors may occur. Therefore, when detecting waveforms and crooked waves other than sine waves, please choose a clamp-on ammeter that can directly test the true RMS value.
3. 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. The ground 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 (amendment of electrical equipment technical standard in 1997), the leakage current clamp meter is gradually used for detection in buildings and factories that cannot be powered off.
