This is a very simple circuit that can detect electromagnetic radiation. The circuit can even detect hidden wrings. A 1mH inductor is used to sense the electric field.
Induces a small electric field sensor inductance voltage, this induced voltage amplification opamp.The headset connected to the output of the operational amplifier audio instruction field. For example, the electric field around the power transformer 50 Hz hum can be heard. R4 pot can be used to adjust the gain of the amplifier. By keeping inductance sensor near a telephone line, you can even hear the telephone conversation. Circuit diagram and parts list Precautions In general PCB assembly circuit. The circuit can be powered from a 9V PP3 battery. This is better for the radial inductor L1. R4 pot can be used to adjust the gain. A switch S1 to ON / OFF switch sliding. You must install IC1 holders. All electrolytic capacitors must be rated for at least 15V.