Can a multimeter be used to detect poor contact of the common neutral line?
Look, many people actually think that only when the neutral wire is disconnected, it causes zero drift. In fact, this is not the case. When the connector is loose but not disconnected (when starting a few hundred watt appliance), anyone will measure it if it is disconnected. However, when it is loose, there will definitely be people who do not know how to measure it. In fact, it is simple. At your distribution room or distribution box, which is your superior distribution room (there should be three-phase electricity), measure the voltage of each phase using a 220V voltage range. Under normal circumstances, each phase is the same (there may be small errors), but when the neutral wire is loose, the performance is different for the three phases. Do you understand? As the virtual connection deteriorates, the voltage difference becomes larger, but this method is only effective when the circuit is quickly disconnected.
Another method is to observe that when the neutral wire is not connected properly, whenever a higher power electrical appliance is used, if you turn on the light, you will see the flickering of the lamp, which is a manifestation of the early stage. However, it is recommended that you regularly check the circuit to avoid such problems as much as possible, which will definitely cause losses.
The steps to test the quality of a capacitor with a digital multimeter are as follows:
1. To determine the polarity, first set the multimeter to the 100 or 1K ohm range. Assuming one pole is positive, connect the black probe to it and the red probe to the other pole. Record the resistance value, then discharge the capacitor to make the two poles contact. Then change the probe to measure the resistance. The black probe with the highest resistance value is connected to the positive pole of the capacitor.
2. Set the multimeter to the appropriate ohm range. The principle for selecting the range is: 20K range for 1 μ F capacitors, 2K range for 1-100 μ F capacitors, and 200 range for capacitors greater than 100 μ F.
3. Then connect the red pen of the multimeter to the positive pole of the capacitor and the black pen to the negative pole of the capacitor. If the display gradually increases from 0 and finally displays the overflow symbol 1, the capacitor is normal. If it always displays 0, the capacitor is internally short circuited. If it always displays 1, the capacitor is internally open circuited.
