Theoretical Analysis of SAW Device and Application as Temperature, Humidity and UV Sensors
Date Issued
2011
Date
2011
Author(s)
Tsai, Chi-Ju
Abstract
In this research, IDT is developed on piezoelectric substrate LiNbO3, Quartz and
LiTaO3. The insertion loss of the device is measured and is compared with the
impulse-function model. In the temperature experimental result, the center frequency
of SAW device is shifted from temperature perturbation.Tthe sensitivity of the SAW
device for temperature is in the order of 10-2°C.
In general, the velocity or insertion loss of SAW device is affected by
acoustoelectric interaction and mass loading. Consequently, Zinc-Oxide is developed on
LiNbO3 substrate in order to generate photoelectric effect with UV light. In this research,
a SAW device with UV detecting area is fabricated, the light wave length between
330nm and 400nm is analyzed, and a sensitivity in the order of W / cm2 is found. It
is note that the dynamic response of SAW light sensor is excellent for 400nm light
length. By combing slanted finger interdigital transducers and plural optically active
areas, an array photodetector can be achieved. This array photodetetor can obtain
multiple UV light intensities within a single measurement.
Finally, we discuss the effect of liquid loading and the vapor in the air condense
into dew on the SAW device surface, A humidity sensor is developed by using cooling
chip to cool down the SAW device to the dew point temperature. By measuring the dew
point temperature and room temperature, the humidity is obtained from SAW humidity
sensor with high accuracy.
Subjects
SAW device
UV sensor
Slanted IDT
Temperature-humidity
Zinc-Oxide
Type
thesis
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