How to measure the insulation resistance of a 750w motor coil to the shell with a multimeter
If you use a multimeter to measure the insulation resistance between the coil and the shell of a 750-watt motor, it may not be so intuitive. Even if the resistance switch reaches 10K, the measured resistance is still infinite, so use a multimeter to measure the motor coil. The insulation resistance to the case is unrealistic.
To measure the insulation resistance of the motor coil and shell, it is best to use a megohmmeter. Place the two probes of the megohmmeter on the coil and motor shell, and then shake the megohmmeter. If the resistance is greater than 2M, it is normal. The larger the resistance, the greater the resistance of the motor. The better the enclosure is insulated. If the resistance value is less than 2M, it means that the motor has leakage and cannot be used.
Set the multimeter to the resistance setting, and touch the red test lead and the black test lead to the terminals and motor casing of the motor respectively. Then move the resistance setting of the multimeter from low to high, and observe the multimeter's display. You will get the insulation resistance of the coil to the casing.
Why does a multimeter become useless after being left with the battery installed for a long time?
There are generally two types of multimeters we often use: the first type is a mechanical multimeter. The second type is an electronic multimeter.
Both types of multimeters require batteries as their power source. Generally, it is one cell of No. 2 1.5Ⅴ battery and one cell of 9V laminated battery.
If the multimeter is not used for a long time, it is best to place it in a dry and ventilated environment, turn off the power switch, and preferably remove both batteries. To prevent the electrolyte from leaving the battery for too long, it will corrode the contact pieces of the positive and negative poles of the meter power supply. In the worst case, an oxide film will appear on the contact piece, affecting the power contact. In severe cases, the copper plates on both poles will be completely corroded, and the corrosion will be light. Use a knife or sandpaper to clean the oxides on the corroded layer. If the positive and negative electrode connectors are completely corroded, replace the connectors.
When the multimeter is not used for a long time, it is best to take out the battery and put it in a dry and ventilated place and package it in a wooden box to avoid moisture.
