The principle of the non-contact electric pen is the principle of electromagnetic induction. When the non-contact electric pen is close to the live wire, it will be processed by the electric pen's internal circuit to make the LED light up and the buzzer sound.
The non-contact electric pen is also called the induction electric pen. When the electric pen is close to the live wire, the alternating current has electromagnetic radiation in the space. After the electric pen antenna receives, filters, amplifies, and compares, it controls the LED to emit light and the buzzer to sound. The non-contact electric pen can only be measured by relying on changes in the magnetic field, so it can only be used for alternating current tests, and cannot measure direct current. It is easy to distinguish between neutral and live.
The non-contact electric pen circuit design includes the electromagnetic induction part and the triode amplifier circuit. An I-shaped inductor is used as an antenna, and several triodes are combined as an amplifier circuit. One end of the inductor is connected to the b pole of the triode, and the other end is suspended. When the inductor is close to the live wire, a weak current is induced. After the first-stage amplification of the triode, the LED is lit and the buzzer sounds, so as to judge the zero live wire.
The LED and the buzzer are mainly used for prompting. The LED will light up and the buzzer will sound when a live wire is detected. On the contrary, it is detected that the zero line LED is off and will not light up, and the buzzer will not sound. The LED and buzzer are designed in the circuit, allowing people to visually distinguish the live wire and the neutral wire.
