Parasitic Effects and Readout Corrections of LC Sensing System

Inductor-capacitor (LC) sensors have several merits compared to traditional sensors, such as no power supply, fully passive components, and wireless telemetry. In practical applications, the accuracy of the readout signals of LC sensors will be affected by changes in readout distance and parasitic effects. This article establishes a complete model of LC sensing system and analyzes the influence of parasitic effects on the readout signal. Theoretical and experimental results indicate that parasitic capacitance at the readout end has a significant impact on the readout frequency over a long readout distance, while the electric field coupling capacitor only has a limited impact on the readout frequency within a very short readout distance. Based on parasitic effect analysis, the formula correction method and de-embedding correction method are proposed to improve the readout signal of LC sensors. Experimental results show that the frequency variation of the formula corrected results is less than 0.14% in the readout range of 3–16 mm, and the de-embedding corrected results show zero variation in the readout range of 2–10 mm. The theoretical analysis and correction approaches provided here are beneficial for improving the readout accuracy of LC sensing systems.