Graduation Year

2011

Document Type

Thesis

Degree

M.S.M.E.

Degree Granting Department

Mechanical Engineering

Major Professor

Frank Pyrtle III, Ph.D.

Committee Member

Nathan Crane, Ph.D.

Committee Member

Craig Lusk, Ph.D.

Keywords

Modified Wien Oscillator, Pyroelectricity, Signal Amplification, Voltage Output

Abstract

This thesis describes the study of the thermal response of the pyroelectric material named lithium tantalate or LT (LiTaO3) in aid of this material’s possible use for temperature measurement. The temperature range studied was between 5-99 oC. The sensor was excited using a silicon rubber heater. The lithium tantalate sensor and the rubber heater were enclosed such that the temperature would reach steady state faster. The enclosure was a small insulated box in order to reduce any extraneous effects on the sensor. The output signal of the lithium tantalate sensor was then amplified by using four different amplifying circuits and the voltage output was studied. The amplifying circuits included Current Mode, double Current Mode, Voltage Mode, and a modified Wien Oscillator.

Results demonstrated linear dependencies of the voltage output as a function of temperature for the Voltage Mode and the modified Wien Oscillator. Using the modified Wien Oscillator amplifying circuit the slope of the line a 2.1mV/oC and for the Voltage Mode the slope was 1mV/oC. For both cases it was found that the range for the standard deviation of the measurements was 0.5<<1mV and the correlation coefficient R2 was above 0.98. Results are comparable to theoretical results for the same amplifying circuits simulated with OrCAD Family Capture Lite Edition and PSpice 9.2 software.

The data showed that the lithium tantalate sensor could be used as a temperature measuring device for the range mentioned above. The resolution of the data is high enough to be able to be detected with modern measuring devices and the standard deviation is low enough to allow for such measurements. Moreover, the linear dependence of the data allows for accurate measurements at each temperature within the range

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