Temperature and Pressure Composite Measurement System Based on Wireless Passive LC Sensor

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 S-11 (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 LC temperature-pressure sensor. By analyzing the resonance frequency and the amplitude of S-11, temperature and pressure were measured simultaneously with a single LC 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 degrees C-300 degrees C and 300 degrees C-1000 degrees C were only 2.89% and 1.25%, respectively. From 25 degrees C to 300 degrees C and 300 degrees C to 1000 degrees 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 LC multiparameter sensors.