How is it that the multimeter measures the short circuit of the line and shows the resistance value?
Here's the thing. I've met it many times:
Before the circuit is powered on for the first time, I will use a multimeter to switch on and off the circuit for short circuit. At this time, everything is normal, and the multimeter shows infinity without buzzing.
After several months of use, during routine maintenance, the multimeter is used to switch off the short circuit of the gear. When the stylus is connected to two wires, it will beep once, and then there will be no sound. The multimeter screen shows that there are more than 60 to 80 resistances.
So I don't know if this is a short circuit or not, and the brake can be closed, so I feel puzzled.
1. At first, the two wires had no resistance. When they were used for a period of time, when they were rechecked, the zero line of the fire was actually turned off with resistance, and the buzzer sounded. I saw this situation in normal practice, and the judgment was as follows:
2. The known condition is that there is no resistance between wires when they are used after indoor installation and debugging. How come there is no resistance between wires after users have used them for a period of time? Is this wire leakage? This phenomenon is the most sensitive problem for the official electrician of the country. His first reaction is to use a shaking table. Without a megger, the problem cannot be found out. This phenomenon is the same as that of old doctors and young doctors. Old doctors know what's wrong as soon as they hear the chief complaint, while young doctors rely on instruments.
3. I often use the 400V electrodeless capacitor on the energy-saving lamp as a resistor, and take down the neon tube up converter on the old fluorescent lamp and connect it in series as an indicator lamp, because this type of indicator lamp has been seen in mobile sockets. The electrodeless capacitor has a feature that it can store a certain amount of charge. If you pass electricity, you will have an electric induction when you touch it carelessly.
4. When rechecking the resistance value, it is only reflected twice, and then it is gone, which is the example I cited above.
5. When there is a mobile socket on the user's wall socket, there is a switch and an indicator light on the mobile socket. After the main power supply is turned off, the mobile socket is not unplugged. (My experience is summarized, all plugs and indicators are prompted to be unplugged.) It is this indicator light that causes the zero line of the fire to be connected.
I don't know the specifications, model, length and erection environment of the wire. The new wire has no sound and no resistance, which means it is normal. After use, the inter-line electricity will easily interfere with the digital multimeter. It is suggested that the wire to be tested be short-circuited and then tested, or tested with a shaking table is more real.
If you really want to measure the resistance value, you should use a shaking table or an insulation resistance meter, or at worst, you should adjust it to the resistance file. What is the matter with measuring the resistance value with the on-off file?
If you still want to measure the resistance, you usually have to cut off the power and then unload the load, otherwise it is meaningless to measure it directly.
For example, if it happens that there is only an incandescent lamp connected between your zero fire lines, it is the resistance of the filament of the incandescent lamp. If it is a fluorescent lamp, it is the equivalent resistance of all the circuits inside the fluorescent lamp.
