Wireless Temperature Sensing System Performance Characterization

Current technology in temperature measurement and control requires labor-intensive and costly installation of sensors, wires and circuitry for thermal-vacuum (TVAC) testing of a system and/or post-deployment management of the thermal environment and performance. In addition, post-installation changes are often costly or impossible once the mission is initiated. Wireless thermal metrology is an enabling technology to obtain temperature history in an area of interest via wireless sensors. In a previous paper [1], we discussed the development of a wireless thermal sensing and mapping system designed for ground testing and in-flight use. We explained the basic instrument configuration for wireless temperature measurement and the analytical modeling for characterizing signal strength, transmission and quality. Laboratory test results indicated that the system is feasible and well-suited for aerospace applications. Predictive capabilities showed excellent agreement with fundamental physics of the signal propagation and the measured data. This paper complements the previous work. First, we describe the development of bounding analytical models to demonstrate the signal leakage from grounded and ungrounded Faraday cages at high frequencies. Then, we describe the development of a predictive model for performance characterization of a wireless thermal sensing system inside a Faraday Cage. Finally, we compare the test results with predictions and characterize the electromagnetic (EM) leakage from the cage when the equipment is placed in various configurations. Preliminary frequency response results assist in understanding EM leakage from the wireless equipment, and provide guidelines for optimal placement of equipment and sensors when tests in Faraday cage-like TVAC chambers are performed.