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When, for example, a mass is deposited onto
a resonator (e.g., a quartz crystal microbalance), there is always a
temperature change accompanying the mass change. The temperature change is caused by the
heat of adsorption, and by the heat emitted by the evaporation source. The frequency change due to mass deposition
is due to the combined effects of the mass change and the temperature change.
The dual mode technique yields two equations with two unknowns which allows
the separation of the mass change induced frequency change from the
temperature caused frequency change.
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The mass change alone can be determined
without having to calibrate the beat frequency, f, as a function of temperature. However, by calibrating the f as a function of temperature, one may, for example,
perform surface studies as a function of temperature.
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D. E. Pierce, Y.
Kim, and J. R. Vig, "A temperature insensitive quartz microbalance,“ Proc. 1997 IEEE Int’l Frequency Control Symp.,
pp. 41-48.
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J. R. Vig,
“Dual-mode Oscillators for Clocks and Sensors,” Proc. 1999 IEEE Int’l
Ultrasonics Symposium
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US Pat. No. 5869763,
J. R. Vig and R. L. Filler, "Method of measuring mass change using a
quartz crystal microbalance," Feb. 1999.
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Y. Kim,
“Sensing of organic vapor adsorption on gold using a temperature insensitive
microbalance,” Proc. 1999 IEEE Int’l Frequency Control Symp.
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