Title :
A surface acoustic wave mercury vapor sensor
Author :
Caron, Joshua J. ; Haskell, Reichl B. ; Libby, Derek G. ; Freeman, Carl J. ; Vetelino, John F.
Author_Institution :
Sensor Res. & Dev. Corp., Orono, ME, USA
Abstract :
A sensor for the in situ detection and measurement of low concentrations of gaseous mercury is presented. The sensor is based upon a dual delay line SAW oscillator with a gold-coated delay path. Gaseous mercury interacts rigorously with the gold film, forming an amalgam. The resulting increase in film mass is manifested as a decrease in oscillation frequency. Measurement of gas concentration is achieved by differentiating the sensor response at room temperature or by operating the sensing element at a temperature where gas-film reaction kinetics result in equilibrium rates of mercury amalgamation and desorption. This equilibrium value of amalgamated mercury is highly dependent upon the gas concentration. Thus, the delay line oscillation frequency is a sensitive measure of gaseous mercury concentration. Responses of this sensor to gaseous mercury concentrations in the ppb range are presented. The sensor response features are analyzed in terms of response shape, response magnitude, response time, and linearity at 25°C and 200°C
Keywords :
chemical equilibrium; chemical variables measurement; desorption; gas sensors; mercury (metal); reaction kinetics; surface acoustic wave delay lines; surface acoustic wave oscillators; surface acoustic wave sensors; 200 C; 25 C; Hg; amalgamated mercury; delay line oscillation; desorption; dual delay line SAW oscillator; equilibrium rates; equilibrium value; film mass; gas concentration; gas-film reaction kinetics; gaseous mercury; gaseous mercury concentratio; gold-coated delay path; in situ detection; linearity; mercury amalgamation; oscillation frequency; response magnitude; response shape; response time; room temperature; surface acoustic wave mercury vapor sensor; Acoustic measurements; Acoustic sensors; Acoustic signal detection; Acoustic waves; Delay lines; Frequency; Gas detectors; Oscillators; Surface acoustic waves; Temperature sensors;
Conference_Titel :
Frequency Control Symposium, 1997., Proceedings of the 1997 IEEE International
Conference_Location :
Orlando, FL
Print_ISBN :
0-7803-3728-X
DOI :
10.1109/FREQ.1997.638534
