Note for megohmmeter:

1. Before measurement, perform an open circuit and short circuit test on the megohmmeter to check whether the megohmmeter is normal. The specific operation is: open the two connecting wires, shake the handle and the pointer should point to infinity, and then short-circuit the two connecting wires, the pointer should point to zero.

2. The device under test must be disconnected from other power sources. After the measurement, the device under test must be fully discharged (it takes about 2 to 3 minutes) to protect the equipment and personal safety.

3. A single-stranded wire should be used to connect the megger and the device under test separately, and the surface of the circuit should be kept clean and dry to avoid errors caused by poor insulation between the wires.

4. During panning, place the megger in a horizontal position, and no short circuit between the end buttons is allowed when the crank is rotating. When testing capacitors and cables, the wiring must be disconnected when the crank is turned, otherwise the megohmmeter will be damaged by reverse charging.

5. When shaking the handle, it should be slow and fast, and evenly accelerate to 120r/min, and pay attention to prevent electric shock. During the shaking process, when the pointer has reached zero, it can no longer continue to shake to prevent heating and damage to the coil in the watch.

6. In order to prevent the surface leakage resistance of the device under test, when using a megohmmeter, the middle layer of the device under test (such as the inner insulation between the cable shell and core) should be connected to the protective ring.

7. The appropriate insulation resistance tester should be selected depending on the voltage level of the equipment under test. Generally, 500V or 1000V megohmmeter should be used for equipment with rated voltage below 500V; 1000～2500V megohmmeter should be used for equipment with rated voltage of 500V and above. In the selection of the measuring range, care should be taken not to make the measurement range exceed the insulation resistance value of the equipment under test, so as to avoid large errors in the readings.

8. It is forbidden to use a megohmmeter to measure in lightning weather or near equipment with high-voltage conductors.