Single-Probe Inductively Coupled In-Circuit Impedance Measurement

Conventional in-circuit impedance measurement setup of the inductive coupling approach requires two inductive probes. This article proposes a single-probe setup for the in-circuit impedance measurement, which not only eliminates the probe-to-probe coupling issue but also simplifies the setup with less instrument overhead. The basic principle behind the proposed setup will be elaborated, followed by experimental validation. To ensure the proposed setup can extract the in-circuit impedance with good accuracy, the required signal-to-noise ratio (SNR) of the setup is carefully studied. In addition, to improve the SNR and the ruggedness of the setup, signal amplification and protection devices are incorporated in the measurement. Finally, the proposed setup is deployed to demonstrate its ability to extract the in-circuit impedance of an energized induction motor.