Wireless Thermal Convection Accelerometer on a RFID-Tag with Heater and Thermal Piles Deposited by E-Beam

Abstract

This paper proposes an innovative method to make a thermal convection accelerometer on an active RFID tag, thus the device is a wireless acceleration sensor and can save more power. The heaters and the thermal piles are deposited by E-beam focused on a target of mixing powders of metals on the RFID tag. Thus the new device is very easy to make. Besides, a hemi-cylindrical chamber and inert xenon (Xe) gas are used to replace the traditional rectangular one with carbon dioxide (CO2). The gas molecular weight of Xe is three times larger than CO2, so the xenon gas inertia is larger and can yield quicker response. Moreover, the proposed hemi-cylindrical chamber is more stream-line in nature, thus it is with less drag effect. Note the device sensitivity when using rectangular chamber and CO2 gas is better at low acceleration. However, the performance is not only begin to decrease for acceleration larger than 18G (1G=9.8 m/s2), but even less than that using Xe gas for acceleration larger than 28G. Contrarily, when using the hemi-cylindrical chamber the device is without the above effects. Comparison of device response for step-input acceleration of 32G is also made; when using rectangular chamber and Xe gas the device response time is 31μs, but it is 60μs for the case with CO2 gas. However, when using hemi-cylindrical chamber and Xe gas the device response time is 15μs, it is about 20.2% of CO2 (74μs). Thus it is better to use either Xe gas or hemi-cylindrical chamber.