Principle: Its internal structure is a light bulb with two electrodes, the bubble is filled with neon gas, commonly known as neon bubble, its one pole is connected to the tip of the pen, and the other pole is connected to the other end of the pen after a high resistance.
When the voltage between the two poles of the neon bubble reaches a certain value, the glow between the two poles will be generated, and the intensity of the glow is proportional to the voltage between the two poles.
When the voltage of the charged body to the ground is greater than the initial glow voltage of the neon bubble, and the tip of the measuring pen is touched by it, the other end is grounded through the human body, so the measuring pen will glow. The function of the resistance in the measuring pen is to limit the current flowing through the human body to avoid danger. Induced current: A current path generated by a change in the magnetic field: as opposed to a break, the circuit is connected.