What's the matter with the resistance value displayed by the short circuit of the multimeter line
the situation is like this
Before the circuit is powered on for the first time, I will use a multimeter to measure whether there is a short circuit in the circuit and it is closing. At this time, everything is normal, the multimeter does not beep, and it also shows infinity.
After several months of use, during routine maintenance, use the multimeter to switch on and off the short circuit. When the test pen is connected to the two wires, there will be a beep, and then there will be no sound. The screen of the multimeter will display 60 to More than 80 resistance values.
So I can't figure out whether it is a short circuit or not, and the gate can be closed, so I feel inexplicable.
1. At the beginning, the two wires had no resistance value. After using it for a period of time, when I came back to check again, there was resistance value when the fire and zero wire were turned off, and the buzzer still sounded. I saw this situation in normal practice, and the judgment is as follows:
2. The known condition is that after indoor installation and commissioning, there is no resistance value between the lines without load when the user uses it. Why does the user have a resistance value between the line and the line without load after using it for a period of time? Is this a wire leak? This phenomenon is the most sensitive issue for the official electrician in the country. His first reaction is to use a shaker. Without a megohmmeter, the problem cannot be detected. This phenomenon is also the same as that of old doctors and young doctors. The old doctor can tell what the disease is when he hears the chief complaint, while the young doctor relies on the equipment.
3. I often use the 400V electrodeless capacitor on the energy-saving lamp as a resistor, and take off the neon tube starter on the old fluorescent lamp and connect it in series as an indicator light, because this type of indicator light has been seen in mobile sockets. The non-polar capacitor has a characteristic that it can store a certain amount of charge. If you pass electricity, if you accidentally touch it, it will have an electric induction on your hand.
4. When rechecking the resistance value, there are only two reflections, and then it will disappear, which is the example I gave 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 is turned off, the mobile socket is not unplugged. Prompt to remove all plugs and indicator lights) It is the fire and neutral wires caused by the indicator lights that are connected.
I don’t know the specification, model, length, and installation environment of the wire. The new wire has no sound and no resistance, which means it is normal. After use, the power between the wires will easily interfere with the digital multimeter due to the power of the wire. It is recommended to short-circuit the wire under test before testing. , or use a shaker test to be more realistic.
If you really want to measure the resistance value, you need to use a shaking meter or an insulation resistance meter. If it is not good enough, you must also adjust it to the resistance level. What is the matter with measuring the resistance value with the on-off level?
If you still want to measure the resistance value, you generally need to cut off the power and then remove the load, otherwise it is meaningless to measure it directly.
For example, if you just connect an incandescent lamp between the zero and live wires, the measured resistance is the resistance of the filament of the incandescent lamp. If it is a fluorescent lamp, the measured resistance is the equivalent resistance of all the circuits inside the fluorescent lamp.
