| Surface acoustic wave(SAW) gas sensor has been widely used in many domains such as environmental monitoring, clinical analyzing, military and security of civilian areas because of its small size, high accuracy, high sensitivity, easy batch production. Meanwhile, because of the features of small size and low power consumption, the SAW gas sensor is particularly suitable for the design of the portable sensor. Under the stable of SAW sensor’s performance, the researching for how to achieve portability of SAW sensor is also a priority.At first, in this paper, the basic principles of SAW sensor and the sensitive gas sensor detection principle were introduced, and based on the SAW oscillator circuit, a sensor circuit has been designed. A power drive circuit, a control circuit for pre-concentrate device, pump working circuit, microprocessor circuit, LCD display circuit, keyboard control circuit, an alarm circuit will be comprised by the control circuit. The control circuit can simultaneously detect three frequency signals which generated by the front end gas sensor oscillation circuit, through controlling the pretreatment device, pump, we process the three frequency signals and displays the detected information.At the same time, the systematic investigation of sensitive layer depositing by air brush coating technology on SAW based two-port resonators are presented. The acoustic devices are coated with chemo sensitive films of different viscoelastic properties and thickness, as ethyl cellulose (ECEL), poly epichlorohydrin (PECH), and Poly (3,4-bishydroxyethylthiophene)(DKAP). Results are presented on both the apparent quality of obtained polymer layers and their performance in sensor characteristics.Finally, the coating film of SAW devices which described in this paper have been test. Through analysis of the test results, adjusting the process parameters of sensitive layer depositing by air brush coating technology on SAW and then the detection sensitivity of SAW gas sensor will be improved. |
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