Measurement methods and experimental verification of impedance of R, L, and C components

Impedance measurement represents a fundamental and critical technology in electronic engineering. This paper investigates precise measurement methods for the impedance of resistors, capacitors, and inductors in AC circuits based on operational amplifier configurations, offering both theoretical insight and practical utility. As a complex quantity comprising real resistance and imaginary reactance, impedance measurement requires simultaneous acquisition of both magnitude and phase information of voltage and current. An I-V conversion circuit is constructed to leverage the virtual short and virtual open characteristics of operational amplifiers, thereby converting the current through the device under test into a voltage signal. A differential amplifier structure is employed to suppress high-frequency virtual ground errors, while stepped adjustment of feedback resistors enhances measurement accuracy. Experimental results demonstrate that under a 1kHz excitation signal, the measurement error for capacitors is less than 2%, for inductors less than 1%, and the phase shift for resistors is nearly 0°. The measured values show strong agreement with nominal values, effectively addressing the limitation of traditional multimeters in measuring complex impedance. This approach enables high-precision characterization of equivalent circuit parameters of components, validating the correctness and practicality of the theoretical analysis and circuit design. Through hands-on implementation, a deeper understanding of the physical concept of impedance and its behavior in AC circuits can be achieved, laying a solid foundation for subsequent applications such as filter design and impedance matching.