Improving the single current probe method of in-circuit impedance measurement

In-circuit impedance measurement has been used in numerous applications, such as impedance characterization during the operation of batteries, power grid, solar panel system, and also power converters. Whereas the voltage-current and the dual current probe methods have been traditionally employed, recently the single current probe (SCP) method emerged as an attractive alternative for its simplicity. Normally, the device under test (DUT) in the SCP method is arranged as a single-turn. However, as shown in this paper, the accuracy of single turn SCP method depends on the characteristic of the current probe itself. In this paper, two different current probes were compared. For preliminary evaluations, 0805 SMD resistors (10kΩ, 5.1kΩ, 1kΩ, 100Ω, 10Ω, and 1Ω) were used as the DUT. This paper also demonstrated that the accuracy could be improved by adding number of turns. One, three, and seven turns were compared. It was found that in general higher number of turns gave higher precision. This was due to increased probe sensitivity as the number of turns increased.