Abstract
Department of Electrical Engineering, National Cheng Kung University, No. 1, University Road, Tainan City 701, Taiwan, R.O.C. 1Department of Computer Science and Information Engineering, Cheng Shiu University, No. 840, Chengcing Rd., Niaosong Dist., Kaohsiung City 83347, Taiwan, R.O.C. 2Department of Electronic Engineering, I-Shou University, No. 1, Sec. 1, Syuecheng Rd., Dashu District, Kaohsiung City 84001, Taiwan, R.O.C. 3Department of Electronic Engineering, Cheng Shiu University, No. 840, Chengcing Rd., Niaosong Dist., Kaohsiung City 83347, Taiwan, R.O.C.
Highlights
The speed of a propagating sound wave is very sensitive to changes in air temperature; air temperature is an important factor affecting the speed of sound.[1,2,3,4] Most ultrasonic systems for air temperature measurement are based on the time-of-flight (TOF) method.[5]
2.1 two-frequency continuous wave (TFCW) method The TFCW-based ultrasonic system for measuring temperature stems from the previously described single-frequency continuous wave method.[1]. Increasing the number of frequencies used for phase comparison will increase the temperature range that can be measured
A TFCW prototype was tested in the chamber by comparing a series of phase shift measurements with simultaneously gathered temperature measurements via the RTD
Summary
The speed of a propagating sound wave is very sensitive to changes in air temperature; air temperature is an important factor affecting the speed of sound.[1,2,3,4] Most ultrasonic systems for air temperature measurement are based on the time-of-flight (TOF) method.[5]. When the TOF method is used to measure the speed of sound, its margin of error is primarily due to an amplitude delay inertia phenomenon and the amplitude attenuation of the received signal.[6,7,8,9]. It can be used to evaluate the ultrasound speed by computing the phase difference between the transmitted and received continuous waves. When the distance between the transmitter and receiver is fixed, we can use phase shift information to determine the variations of the ultrasound speed, which vary with air temperature. Huang et al[1] showed that the measurable temperature range when using the SFCW method is approximately 50°C for one wave period when the distance between the transmitter and receiver is 100 mm. The range of air temperature that can be measured when the distance is 1 m is only about 5°C
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