A Novel Real-Time Capacitance Estimation Methodology for Battery-Less Wireless Sensor Systems

作者：Kim Hwa Soo^*; Sivaramakrishnan Shyam; Sezen A Serdar; Rajamani Rajesh

来源：IEEE Sensors Journal, 2010, 10(10): 1647-1657.

DOI：10.1109/JSEN.2010.2046407

• Battery-less wireless sensor
• capacitance sensing
• inductive coupling
• mutual inductance

This paper presents a novel method to read a passive capacitive sensor in telemetry by using inductive coupling. While classical inductive coupling approaches measure sensor capacitance by identifying the resonant frequency of the sensor with a sweep of radio frequency (RF) signals, the proposed method estimates the capacitance change in real-time by algebraically manipulating two measurements (the magnitude and the phase of the reflected sensor impedance). Only one RF signal is used in the proposed method instead of a frequency sweep. Analysis is provided to show that some physical parameter errors can deteriorate the capability of the proposed method in accurately measuring sensor capacitance. However, the use of a first order calibration procedure based on error analysis overcomes this shortcoming. Extensive experimental results with the proposed method combined with a first order calibration show that multifrequency and rapid changes in sensor capacitance can be estimated reliably under varying locations and orientations of the interrogator. The battery-less wireless sensors enabled by the developed technology in this paper can be widely used for measurement of fluid pressure, force, acceleration and other capacitance-change based sensor measurements.

• 出版日期2010-10