Temperature and Pressure Composite Measurement System Based on Wireless Passive <i>LC</i> Sensor

Abstract

In this article, we proposed a measurement system that can simultaneously measure temperature and pressure. By analyzing several existing measurement methods of the sensor, we determined that the resonance frequency and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S_{11}$ </tex-math></inline-formula> (reflection coefficient) amplitude of the sensor readout system should be measured when the resonance frequency of the sensor up to a hundred megahertz or even gigahertz and when the sensor works in ultrahigh temperature environment. In addition, we designed a simple and accurate sensor readout circuit and an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> temperature–pressure sensor. By analyzing the resonance frequency and the amplitude of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S_{11}$ </tex-math></inline-formula> , temperature and pressure were measured simultaneously with a single <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> circuit. Since the analysis of the whole nonlinear system of sensors is complex, we divide the entire nonlinear system into several linear systems superposition. By analyzing the interference between temperature and pressure, we further optimized the measurement method. The relative errors of the temperature measurements in the range of 25 °C–300 °C and 300 °C–1000 °C were only 2.89% and 1.25%, respectively. From 25 °C to 300 °C and 300 °C to 1000 °C, the average relative errors of pressure measurement were only 4.07% and 4.74%, respectively. Besides, the proposed method can also be widely used in the measurement of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> multiparameter sensors.