Capacitive Sensor Interfaces: Signal Conditioning Techniques—A Review

Abstract

Capacitive sensors are extensively utilized in manufacturing to detect surface property variations, level sensing, and proximity sensing in assembly lines. They provide feedback to robotic arms, integrate with machine tools to monitor tool wear, control static electricity, and assist in materials sorting and positioning. To ensure their outputs are compatible with subsequent processing equipment, capacitive sensors often incorporate signal conditioning units. These units are crucial for optimizing sensor performance, converting capacitance changes into voltage, current, frequency, or time duration signals, and providing amplification, impedance matching, filtering, and linearization. Linearity is a vital design parameter for capacitive sensors, ensuring accurate and consistent measurements across various applications. Achieving linearity simplifies calibration, enhances predictability and maintains a direct proportionality between the sensor’s output and the measured parameter, thereby improving the overall reliability and performance of the sensing system. This review article comprehensively analyzes the signal conditioning techniques used in capacitive sensors, emphasizing the importance of linearity. By exploring these techniques, the article offers valuable insights that guide the development of more accurate, reliable, and efficient capacitive sensing systems, which are increasingly essential in advanced manufacturing and automation.