Thesis - University Access Only
Master of Science (MS)
Department / School
Bulk and surface acoustic wave devices have been studied as temperature sensors since the early 1960s. Advantages of acoustic temperature sensors are a high resolution, frequency output, and ease of integration with other acoustic sensors. A disadvantage is the need for hermetic packaging which slows sensor response time and increases cost, but is necessary to prevent sensor contamination. Surface skimming bulk wave (SSBW) devices have more recently been studied for signal processing applications and have been found to be less sensitive to aging and much less sensitive to surface contamination than other acoustic devices. Although they have temperature coefficients of up to 40 PPM/°C, there have been no studies of SSBW devices as temperature sensors. The objectives of this work were to study the temperature characteristics and contamination sensitivity of a 150 MHz quartz SSBW device as a temperature sensor, as well as calibration methods. Calibration procedures are an important concern in applications where the temperature sensor must be located close to its electronics and where the electronics are not subject to the temperature being measured. The SSBW ATS was found to have very low sensitivity to contamination as compared to SAW or APM devices. Microscopic levels of contamination should produce temperature deviations of less than 0.01 °C. The temperature coefficient of frequency was found to be 32 PPM/°C with a deviation from a second order curve fit of about 0.2 °C while the 3 Hz short term stability of the SSBW oscillator could provide a temperature resolution of about 0.001 °C. Although the ATS was successfully calibrated with two of the techniques where the ATS was remotely located with extension cables, removing the cables required single point re-calibration. When the cables were coiled up with the sensor electronics, errors of about 1 °C resulted due to the movement of the cables. These results suggest that 'non-hermetically sealed SSBW devices could be used as temperature sensors where integration with another sensor or a digital output is desired. An in-situ calibration procedure is needed to eliminate the need for single point re-calibration after the ATS is placed in its application.
Library of Congress Subject Headings
Acoustic surface wave devices Thermometers
Number of Pages
South Dakota State University
Wold, Cyle E., "A Surface Acoustic Wave Thermometer" (1999). Electronic Theses and Dissertations. 665.