Low-Cost Wireless Temperature Measurement: Design, Manufacture, and Testing of a PCB-Based Wireless Passive Temperature Sensor.

Dan Yan,Xiaoyong Chen,Ting Liang,Zong Yao,Yong Yang,Jijun Xiong,Yingping Hong

doi:10.3390/s18020532

Abstract

Low-cost wireless temperature measurement has significant value in the food industry, logistics, agriculture, portable medical equipment, intelligent wireless health monitoring, and many areas in everyday life. A wireless passive temperature sensor based on PCB (Printed Circuit Board) materials is reported in this paper. The advantages of the sensor include simple mechanical structure, convenient processing, low-cost, and easiness in integration. The temperature-sensitive structure of the sensor is a dielectric-loaded resonant cavity, consisting of the PCB substrate. The sensitive structure also integrates a patch antenna for the transmission of temperature signals. The temperature sensing mechanism of the sensor is the dielectric constant of the PCB substrate changes with temperature, which causes the resonant frequency variation of the resonator. Then the temperature can be measured by detecting the changes in the sensor’s working frequency. The PCB-based wireless passive temperature sensor prototype is prepared through theoretical design, parameter analysis, software simulation, and experimental testing. The high- and low-temperature sensing performance of the sensor is tested, respectively. The resonant frequency decreases from 2.434 GHz to 2.379 GHz as the temperature increases from −40 °C to 125 °C. The fitting curve proves that the experimental data have good linearity. Three repetitive tests proved that the sensor possess well repeatability. The average sensitivity is from repetitive measurements conducted three times. This study demonstrates the feasibility of the PCB-based wireless passive sensor, which provides a low-cost temperature sensing solution for everyday life, modern agriculture, thriving intelligent health devices, and so on, and also enriches PCB product lines and applications.

Highlights

In various fields such as light industry, modern agriculture, medical care, and even in day-to-day life, there is a need for low-cost temperature monitoring systems, which are capableSensors 2018, 18, 532; doi:10.3390/s18020532 www.mdpi.com/journal/sensorsSensors 2018, 18, 532 of easy integration, taking measurements in low temperature ranges, wireless operation, and in situ temperature monitoring, for the real-time awareness of production safety, standard operation, and personal health monitoring, and so on [1]
Due to the use of a separate temperature sensor and wire connection, there is an increase in the manufacturing cost and interference in measuring temperature, along with an increase in the complexity and difficulty of temperature measurement, system integration, and packaging
A wireless passive temperature sensor based on a PCB substrate is designed

Summary

Introduction

In various fields such as light industry, modern agriculture, medical care, and even in day-to-day life, there is a need for low-cost temperature monitoring systems (sensors), which are capableSensors 2018, 18, 532; doi:10.3390/s18020532 www.mdpi.com/journal/sensorsSensors 2018, 18, 532 of easy integration, taking measurements in low temperature ranges, wireless operation, and in situ temperature monitoring, for the real-time awareness of production safety, standard operation, and personal health monitoring, and so on [1]. In various fields such as light industry, modern agriculture, medical care, and even in day-to-day life, there is a need for low-cost temperature monitoring systems (sensors), which are capable. In greenhouses, it is useful for real-time temperature monitoring in order to adjust the plant’s growth status and to achieve accurate farming. Some of the common uses in day-to-day life include monitoring the temperature of car tanks to prevent overheating and dry burning, and the production of intelligent and portable medical monitoring equipment for the real-time monitoring of human body temperature in order to provide 24 h care to the frail elderly, infants, and patients. The PN junction principle is used to measure the temperature in the literature [8,9] These sensors achieve temperature sensing and contribute to the measurement of temperature parameters. In lead-type temperature sensors, the presence of wires makes it not conducive for the temperature monitoring and measurement of moving entities [10]

Methods

Discussion

Conclusion