Practical Aspects of Impedance Measurement using Operational Amplifier and Oscilloscope

This paper deals with a readout-based low-frequency impedance measurement employing an operational amplifier and a special oscilloscope with frequency response analysis option for automatic measurement of Bode plots. The presented method is known from a point-to-point measurement using standard oscilloscopes and an external generator, but the main real limiting factors are not often evaluated and discussed. Limitations of the method, the real key features of the measurement setup and their impact on the validity of results are discussed in this work. The proposed concept represents a low-cost way of impedance measurement for fast and educational purposes. Measurement results were confirmed by theoretical and simulation ones. Their accuracy satisfies the low-frequency measurement of impedances within indicated limits and for intended purposes.