The working principle of the megohmmeter is that the DC high voltage generated by the internal battery as the power source through DC/DC conversion is from the E pole to the L pole through the tested product, thereby generating a current from E to L pole through I/V After the conversion is completed by the divider, the measured insulation resistance value will be displayed on the LCD directly. The use method and reading of the megohmmeter:

1. The power of the tested equipment must be cut off before measurement, and the equipment must not be charged for measurement to ensure personal safety and equipment safety. Measurements can only be performed after eliminating this possibility;

2. The surface of the measured object should be clean to reduce the contact resistance to ensure the accuracy of the measurement result;

3. Before measurement, the megohmmeter should be subjected to an open circuit and short circuit test to check whether the megohmmeter is in good condition. That is, before the megohmmeter is connected to the measured object. Shake the handle to make the generator reach the rated speed (120r/min), and observe whether the pointer points to the "∞" position on the scale. Short-circuit the terminal "line (L) and ground (E)", shake the handle slowly, and observe whether the pointer points to the "0" position of the scale. If the pointer cannot point to the position of the finger, it indicates that the megohmmeter is faulty. It should be used after maintenance;

4. Correct wiring. Generally, there are three terminals on the megohmmeter. Among them, L is connected to the conductor part insulated from the ground, and E is connected to the outer shell or ground of the measured object. G is connected to the shield of the measured object or the part that does not need to be measured. When measuring the insulation resistance, generally only the "L" and "E" terminals are used. But when measuring the insulation resistance of the cable to the ground or the leakage current of the device under test is serious, it is necessary to use the "G" terminal and connect the "G" terminal to the shielding layer or the shell. After the line is connected, you can turn the crank in a clockwise direction. The shaking speed should be slow and fast. When the rotation speed reaches about 120 revolutions per minute, keep the rotation at a constant speed. Read the reading after 1 minute, and read while shaking, without stopping the reading;

5. Place the megohmmeter in a horizontal position during panning, and no short circuit between the end buttons when the handle is turned. Shaking the handle should be slower and faster. If you find that the pointer is pointing to zero, it means that the insulation under test may have a short circuit. At this time, you cannot continue to shake the handle. To prevent heating and damage of the coil in the watch.