Multimeters, also known as multiplex meters, multimeters, three-meters, multi-meters, etc., are indispensable measuring instruments in power electronics and other sectors. They generally measure voltage, current and resistance as their main purpose. According to the display mode, multimeters are divided into pointer multimeters and digital multimeters. It is a multi-function, multi-range measuring instrument. Generally, a multimeter can measure DC current, DC voltage, AC current, AC voltage, resistance and audio level, etc. Some can also measure AC current, capacitance, inductance and semiconductor Some parameters (such as β), etc.
The multimeter can be used not only to measure the resistance of the object being measured, but also to measure the DC voltage with AC and DC voltage. Even some multimeters can also measure the main parameters of transistors and the capacitance of capacitors. Fully mastering the use of multimeter is one of the most basic skills of electronic technology. Common multimeters are analog multimeters and digital multimeters. The pointer multimeter is a multi-function measuring instrument with a meter head as the core component. The measured value is read by the pointer of the meter head. The measured value of the digital multimeter is directly displayed in digital form on the LCD screen, which is easy to read, and some have voice prompt function. A multimeter is an instrument that shares a meter head and integrates a voltmeter, ammeter and ohmmeter.
It is not suitable for a multimeter to measure the leakage current of 220V, because what you want to measure is leakage current. It is a weak item for a multimeter to measure weak AC current, and it is troublesome to measure it. If you have to measure it, you need to use a current transformer, you might as well Use a clamp meter to measure, but use a clamp meter with a suitable range and better sensitivity.
If the circuit leakage is suspected, it can be judged by a circuit breaker with leakage protection, and the scope of leakage is judged step by step to eliminate the fault.
As for the use of electricity to block the leakage of the measurement circuit, I think it is not appropriate. Since it is a leakage, the resistance between the live wire and the protective ground is not infinite, but the voltage of the multimeter is not enough to explain the insulation between them, that is to say, the insulation resistance is completely different between 9V and 220V. Therefore, the insulation resistance is measured at a voltage higher than the voltage used to obtain reliable data. So it must be used to shake the watch.
Of course, if you just test whether there is a short circuit or a path between the live wire and the protective ground, you can also use a multimeter to block it. It just cannot measure the insulation data between them.
Strictly speaking, a shaker should be used to measure the leakage of the line insulation resistance circuit. The shaker is equivalent to a 1000v or 500v generator. The leakage current passes through the sampling resistor inside the shaker to generate a sampling voltage indication on the resistance. Normally, a stable value greater than 0.5 megaohm is qualified. The internal battery of the multimeter is 9v to 15v, and the resistance file and voltage file can only determine the short circuit, and roughly determine whether it is leaking.
1. Power-off measurement: turn off and disconnect all electrical appliances, use the multimeter RX10K file, one test lead receives the test wire, and the other test lead is grounded (or faucet), it should show infinite resistance, otherwise it will leak.
2. Live measurement: Use a multimeter to measure the metal shell of electrical appliances suspected of leakage. Connect one test lead to the shell and the other to ground (or water tap). When the pointer shows the voltage is higher than 30-50 volts, change Use AC 50 volts. If the power supply is confirmed to be higher than 30 volts, it is a leakage, and lower than 30 volts is normal. Reverse the zero and fire power supply plug wires and measure again to confirm.
3. Leakage measurement between live wire and neutral wire (or live wire and live wire): turn off and disconnect all electrical appliances, measure the resistance between live wire and neutral wire, it should be infinite, otherwise it is leakage.
The above methods have an accuracy rate of 99.9% for troubleshooting, which is convenient, fast and practical. The megohm special shaker is only used in engineering, and the use efficiency is low during maintenance. Only when the multimeter has a good measurement confirmation, but the line does leak, it should be used. Shake the meter, but the leakage cannot be detected by the multimeter.