Improved methodology for testing and characterization of piezodelectric gas sensors

Abstract

An apparatus used for generating test vapours, exposing coated piezoelectric crystals and recording the responses in real time is described. In designing the apparatus, special care was taken to prevent any changes in crystal resonant frequency that could be caused by factors other than the presence of chemical stimulus. Two three-way solenoid valves were used to enable the sensor to be exposed alternatively to clean carrier gas and carrier gas containing sample vapour, while keeping the sensor operating conditions as constant as possible. The experimental data were collected automatically and, simultaneously, stored in a computer memory and sent to a recorder. The described methodology provides sensor response curves that are convenient for display and analysing sensor behaviour. Organophosphorus compounds were used for testing.