First, use a multimeter to measure the leakage voltage, put the multimeter switch on the AC voltage measurement position, generally in the AC voltage 250V position, then insert the black test lead into the soil near the device under test, and connect the red test lead to the metal of the device. on the shell. At this time, look at the indicator on the multimeter. If the needle does not move, you can change it to a low gear one by one until the specific data is indicated, which is the leakage voltage of the device. If there is still no indication when the test pen is at the lowest level, it means that the device has no leakage.