The voltage detection test pen judges whether the DC is grounded.
In a DC system insulated to the ground, you can stand on the ground and use a test pen to contact the positive or negative pole in the DC system. If the neon bulb of the test pen does not light up, there is no grounding phenomenon.
If the neon bulb is bright, it means that there is a grounding phenomenon, and if the neon bulb is bright, it means that the positive electrode is grounded. If it shines on the finger end, it is the negative ground.
