Gas diagnosis by a quantitative assessment of the transient response of a capillary-attached gas sensor

A numerical comparison of the transient response of a capillary-attached gas sensor (CGS) to an unknown target gas (TG) with those previously recorded for reference gases, afforded TG identification. A CGS was fabricated by hermetic attachment of an 80 mm long glass tube of 2 mm internal diameter to a zinc oxide based resistive gas sensor. The normalized transient responses of the fabricated device to hydrogen, methanol, ethanol and butanol were recorded as references. The response to an unknown TG was then compared with the reference profiles after normalization. The means of comparison was the calculation of the square error integrals of the recorded response with respect to the reference profiles. The TG was identified by selection of the reference gas corresponding to the least square error integral calculated. The device could identify an unknown contamination among the references available. The method was proved to be applicable to a wide concentration range. Numerical examples, based on the actual test results, are presented.