A Study of the Interrogation System for Wireless Surface Acoustic Wave Sensor

• Main Authors: Chun-Hsiao Li, 黎俊霄
• Other Authors: none
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/46109741140320277010

碩士 === 國立中正大學 === 光機電整合工程所 === 93 === Applying SAW sensor in smart spindle must select wireless sensor technology, Which is equal to use wireless technique to send the signal. In the case of smart spindle, since the interrogative distance is fixed and inductive coupling is in the range, therefore the signal consumption is pretty low. From the above condition, in this research, I use inductive coupling to achieve the wireless signal transmit. Since the SAW sensor got the variation of sensing quantity, the center frequency would vary, so it is necessary to set interrogation system to got the information of variation. Interrogation system is compose of general commercial IC, it could divide into two parts, measure amplitude and measure frequency. On Measure frequency, measure frequency is used to demodulate the high frequency sensing signal to DC signal. The signal stands for the frequency of sensing signal. On measure amplitude, using circuit to measure the peak value, the output signal stands for the value of sensing amplitude. After that, using A/D card or DSP card to pick signal information from interrogation system. By curve fitting, we can get the variation of the signal from central frequency and get the further information of sensing quantity. In this research, by using the way of changing temperature and wireless framework, we measure the variation of center frequency of the SAW sensor, and the experience result tells us, each degree of the temperature increase, the center frequency of the SAW sensor decade about 585Hz. Comparing with the theoretical quantity 553Hz, there is an error about 5.78% between them.