Liquid level measurement using a single electrode capacitive sensor made of carbon nanotube-paper composite

Abstract Liquid level measurements play a vital role in various fields, including environmental, industrial, and medical applications. While hydrostatic, optical, and ultrasonic sensors are commonly used for this purpose, capacitive sensors have also gained prominence. However, capacitive sensors have inherent limitations in terms of dynamic range and resolution. These sensors consist of a pair of electrodes with a gap, and the size of this gap directly affects the sensor’s dynamic range and resolution. Increasing the gap size enhances the dynamic range but compromises resolution. To overcome this challenge, a novel approach involving the investigation of a single-electrode capacitive sensor is presented. This sensor consists of using a carbon nanotube-paper composite (CPC), which offers unique advantages for measuring liquid levels with improved dynamic range and resolution. The sensing performance of the single-electrode sensor is evaluated in both conductive and non-conductive containers, ensuring its versatility and applicability in different scenarios. Furthermore, the study explores the implementation of a differential configuration for the single-electrode sensor. This configuration aims to enhance accuracy and stability, particularly in achieving femto-Farad level accuracy. By leveraging the potential of the single-electrode capacitive sensor, numerous applications such as liquid level sensing, immersible liquid level sensing, and rain sensing are demonstrated. This result holds potential for advancing liquid level measurement capabilities across various industries and opening up new opportunities for sensor applications.