Wireless Real-Time Transistor-Based Skin Temperature Data Acquisition System

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Environmental physiology studies rely on the accurate measurement of skin and internal temperatures. Many traditional skin temperature systems utilize thermistor or thermocouple measurements. However, utilizing a transistor-based sensor allows for a more linear data set, which could provide more stability, thus allowing for a more robust and accurate measurement over a range of environmental conditions. Field Programmable Gate Arrays (FPGA) are relatively low cost and low power consuming programmable hardware devices that allows for a signal to be processed and viewed in real time. Combining the processing power of the FPGA and the heightened accuracy of transistor-based analog temperature sensors, a modernized data acquisition (DAQ) system could provide linearized real time data. PURPOSE: To design a wireless patch-type transistor-based skin temperature DAQ system that will provide a more accurate and linear set of data for measurement in hot/humid/cold/altitude environments, and will be sufficiently robust for outdoor field studies. METHODS: We designed and built a prototype wireless transistor-based skin temperature DAQ that implements a precision analog temperature sensor to acquire skin temperature and FPGA technology for signal processing. The tested accuracy for the precision analog temperature sensor is ±0.05-0.1°C in a temperature range of 20°C to 42°C. By utilizing FPGA technology, the system will process, pack, and wirelessly send data to a computer for real time monitoring. RESULTS: In preliminary testing, the FPGA system showed an overall lower power consumption in addition to less variability in Voltage (V), the signal upon which temperature measurements depend. Over a 5°C temperature change it was seen that the FPGA system had a variance of 3.7*10^(-11) V, while a thermistor based temperature system had a variance of 1.3*10^(-3) V. In most settings, this will result in a substantially lower power consumption using our new system. CONCLUSION: Our data suggest that our new FPGA approach is superior to traditional skin temperature measurements in its ability to rapidly attain and maintain accurate temperature readings. Next steps include field testing the device over a wide range of temperature, wind and humidity conditions. Funded by USAMRMC; author views not official US Army or DOD policy.