Study on selectivity enhancement of tin dioxide gas sensor using non-conducting polymer membrane

A non-conducting polymer membrane can be used as a molecular sieve to enhance the selectivity of a tin dioxide gas sensor. A commercial polymer, polyimide XU218 of the Eiba-Geigy company, is coated on the surface of a tin dioxide gas sensor FIGARO TGS842 which was designed to detect methane. The polymer coated sensor is calibrated in a high accuracy testing system which is controlled by a PC with GPIB and mass flow controllers (MFCs). Three gases, hydrogen, methane, and ammonia, are used to investigate the response of the sensor. It is found that the sensor shows a characteristic change in response to ammonia and an almost negligible change in response to hydrogen and methane.