How to measure leakage with multimeter
Multimeters, also known as multimeters, multimeters, three-meters, multimeters, etc., are indispensable measuring instruments in power electronics and other departments. Generally, the main purpose is to measure voltage, current and resistance. Multimeters are divided into pointer multimeters and digital multimeters according to the display method. It is a multi-functional and multi-range measuring instrument. Generally, the multimeter can measure DC current, DC voltage, AC current, AC voltage, resistance and audio level, etc., and some can also measure AC current, capacitance, inductance and semiconductor. Some parameters (such as β) and so on.
The multimeter can be used not only to measure the resistance of the measured object, but also to measure the DC voltage. Some multimeters can even measure the main parameters of transistors and the capacitance of capacitors. It is one of the most basic skills of electronic technology to be fully proficient in the use of multimeters. Common multimeters include pointer multimeters and digital multimeters. The pointer multimeter is a multi-functional measuring instrument with the meter head as the core component, and 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 by the liquid crystal display, which is easy to read, and some also have a voice prompt function. A multimeter is a meter that combines a voltmeter, an ammeter and an ohmmeter in one head.
The problem of measuring 220V leakage with a multimeter is not suitable, because what you want to measure is the leakage current. The multimeter is weak in measuring weak AC current, and it is troublesome to measure inaccurately. If you insist on measuring, you need to use a current transformer. Use a clamp meter to measure, but choose a clamp meter with a suitable range and better sensitivity.
If you suspect that the circuit is leaking, you can use a circuit breaker with a leak protection to judge, judge the range of the leakage segment by segment, and troubleshoot.
As for using electricity to block the leakage of the measurement line, I don't think it is appropriate. Because 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 at 9V is completely different from that at 220V. Therefore, the insulation resistance is measured at a condition higher than the electrical voltage to obtain reliable data. So you have to use a shaker.
Of course, if you just test whether there is a short circuit or a path between the live wire and the protective ground, it is also possible to use a multimeter to block it. Just can't measure the insulation data between them.
Strictly speaking, a megger should be used to measure whether the line insulation resistance circuit is leaking or not. The megger is equivalent to a 1000v or 500v generator. The leakage current passes through the sampling resistor inside the megger, and a sampling voltage indication is generated on the resistance. Under normal circumstances, a stable value greater than 0.5 megohm is qualified. The battery inside the multimeter is 9v to 15v. The resistance and voltage files can only determine the short circuit, and roughly judge whether there is leakage.
1. Power-off measurement: turn off and disconnect all electrical appliances, use a multimeter with RX10K gear, one test lead is connected to the live wire, and the other test lead is grounded (or faucet). It should show infinite resistance, otherwise there will be leakage.
2. Live measurement: Use a multimeter with a 250-volt AC voltage range to measure the metal shell of the electrical appliance that is suspected of leakage. One test lead is connected to the shell, and the other test lead is grounded (or the faucet). When the pointer shows a voltage higher than 30-50 volts, replace it 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. Then swap 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 accuracy rate of the above method for troubleshooting is 99.9%, convenient, fast and practical, and the megohm special shaker is only used in engineering, and the use efficiency is low in maintenance. Only when the multimeter is confirmed to be good, but the line is indeed leaking, can it be used Shake the meter, but the leakage cannot be detected by the multimeter.
