Miniaturized gas monitoring system employing several SAW sensors

We have developed a compact gas monitoring system which is able to run up to four different SAW sensors. Additionally, four conductivity type sensors can be integrated. Besides the sensors themselves a major part of the device is an ASIC managing system control and data acquisition, i.e. both the handling of several RF signals and the control of the measuring conditions. A PCMCIA interface. has been included providing a standardized connection to a laptop for readout. It enables the data transfer and quick changes in the measuring procedure. The set-up of the system, especially the control of the sensor temperature and the sensor data acquisition, is discussed. At present we have integrated two sensors with differently deposited copper phthalocyanine films on self-designed 80 MHz-SAW filters with additional conductivity probe patterns differently responding to O₃ and NO₂. Additionally, a similar SAW sensor with a hyperbranched polyester film is able to measure NH₃ concentrations. The sensor design and preparation together with the resulting gas detecting properties of these devices are explained. The sensors proved to be capable to detect those gases down to the ppb concentration range. Results obtained with a test device of the gas monitoring system as a whole are discussed. The device comes out as an opportunity for an easy and handy multi-component gas analysis