A sensor for the in situ detection and measruement 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 mercuary interacts with the gold film,forming an amalgam.The resulting increase in film mass is manifested as a decrease in oscillation frequency.Measurement of gas ocncentration is chieved by operating the sensing element at a temeprature where gas-film reaction kinetics result in equilibrium rates of mercury amalagmation and desorption.This equilbrium value of amalgamated mercury is highly dependent upon the gas ocncentration.Thus,the delay line oscillation frequency is a sensitive measure of gaseous mercury concentration.
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