1. Determine whether the circuit or device is live or not

The usage is as follows: Set the multimeter to the AC20V position, with the black lead hanging in the air, and hold the red lead in contact with the line or device on the side. At this time, the multimeter will display a number. If the number displayed is between a few volts to more than ten volts (different multimeter displays different values), it indicates that the line or device is live. If the display is zero or very small, it indicates that the line or device is not live.

2. Distinguishing whether the power supply line is a live line or a neutral line

The second method: does not require contact with the measured circuit or device. Set the multimeter to AC2V position, with the black lead hanging in the air, and hold the red lead in hand to gently slide the tip of the pen along the line. At this time, if the meter shows a few volts, it indicates that the line is live.

3. Find the break point of the cable

First, use a resistance gauge to determine which cable core wire has broken circuit. Then connect one end of the broken core wire to the AC220V power supply. Then, set the multimeter to the AC2V position, with the black probe hanging in the air, and hold the red probe to gently slide the tip of the pen along the line. If there is a voltage of a few volts or a few tenths of a volt (depending on the cable) displayed on the meter, and if it moves to a certain position, the display on the meter suddenly decreases a lot, Write down this position: generally. The breakpoint is located between 10-20cm in front of this position.

4. Measure the frequency of UPS power supply

You can connect a 220V/6V or 220V/4V step-down transformer to the output terminal of the UPS power supply, reduce the voltage without changing the frequency of the power supply, and then connect the frequency shift to the output of the transformer to measure the frequency of the UPS power supply.