How to measure the insulation protective layer of wires with a multimeter
Multimeters can only normally measure voltage, current and resistance or others. A multimeter simply cannot measure the insulation properties of a wire.
Wires and cables are tested by local quality and technical supervision bureaus or testing centers using special testing instruments, or the manufacturers are entrusted with testing themselves.
According to the standard of GB/T5023.3-2008, for example, the commonly used polyvinyl chloride (PVC) copper core wire or power cable BV450/750 1×1.5 wire requires a length of 5 meters. In a specially customized water tank, Let the water temperature gradually rise to (temperature 70±2℃) and soak for no less than 2 hours. The insulation resistance value should be determined by applying the corresponding DC voltage on a professional testing instrument. This process should be carried out in 5 times in total.
The DC voltage of the internal power supply battery of the multimeter used by people is generally 9V. This voltage does not have enough ability to determine and detect the insulation performance of the wire.
It is best to use a megger to measure cable insulation. The results measured by a multimeter are not accurate and can only be estimated. However, the cable insulation is seriously damaged, so it is more convenient to use a multimeter to find out the problem. The resistance between lines must be greater than 1M ohm. If it is less than 1M, be careful when using it, but you must rule out water or moisture in the cable. If so, it must be dried before testing.
Use a multimeter to check whether the filter is good or bad
If there is an internal circuit break in the filter, the inverter will stop working, because the filter is usually connected in series to the power supply of the inverter.
If the filter fails, it may cause interference to the equipment around the inverter, which may cause the elevator to work abnormally, or the equipment around it to not work properly, resulting in noise, abnormal movement, etc. In serious cases, Will cause damage to these sensitive electromechanical equipment
The difference between active filters and passive filters:
1. Active filters are electronic, while passive filters are mechanical;
2. The active filter detects a certain harmonic order and then cancels it. The passive filter forms a certain harmonic channel through the cooperation of the reactor and the capacitor to absorb the harmonics;
3. Use passive filters because of capacitors.
For the surface acoustic filter, its two input pins 1 and 2, its two output pins 3 and 4, and the input and output pins are insulated (as shown in the figure), and they are all insulated from the shielding pin 5. Therefore, when measuring the resistance between two using the R×1 k Ω range of a multimeter, it should be ∞. If there is a resistance of hundreds or thousands of ohms, it indicates that the performance of the surface acoustic filter has deteriorated. If the resistance is very small, it indicates that the surface acoustic filter has broken down.
