Eliminating the Effect of Probe-to-Probe Coupling in Inductive Coupling Method for In-Circuit Impedance Measurement

The in-circuit impedance serves as a key parameter for evaluating the operating status and health condition of many critical electrical assets. For its noncontact nature and simplicity in on-site implementation, the inductive coupling approach is an attractive method to extract the in-circuit impedance of an electrical system. In some practical situations where there are space constraints, the inductive probes used in this approach are very close to each other and the probe-to-probe coupling between inductive probes cannot be ignored. This article investigates possible errors due to such coupling and proposes an open-short-load calibration technique and a proper measurement process to minimize the error in the measured in-circuit impedance.