Electric field probe using a differential amplifier circuit with high input impedance

Switching of power electronic equipment mounted in vehicles generates unwanted electromagnetic radiation and interferes with radios. In particular, it is difficult to secure performance in the AM radio band because its frequencies are near switching frequencies. In order to reduce extraneous electromagnetic radiation from power electronic equipment, identifying noise sources and propagation paths by measuring electric fields near equipment with probes is effective, but in AM radio and other low-frequency bands, the sensitivity of electric field probes dropped and measurement was difficult. We developed a high-sensitivity electric field probe using a differential input amplifier circuit with high input impedance. Also, as an example of measurement, the near electric field when a DC motor was driven with PWM was measured and the radiation source was identified.