Application of a Fringe Capacitive Sensor to Small-Distance Measurement

Abstract

In this paper, we used a fringe capacitive sensor to measure a short-distance variation of a target. High-precision displacement measurement was carried out based on the small fringing capacitance of the sensor measured. Sensing sensitivity was 38 µV/µm when the measurement was carried out in the distance range from 75 to 150 µm, which is the distance range between the sensor and the target. The sensitivity of the fringing capacitor is affected by its dimension, linewidth, and pattern. A printed circuit board (PCB)-based fabrication process was used to fabricate fringing capacitive sensors of various patterns. A simple and low cost sensing circuit transformed fringing capacitances into voltage output signal, which is also called capacitance-to-voltage (C/V) conversion. We accomplished the short-distance measurement with precision up to a submicron level.