A novel method for the evaluation of the kinetic parameters of the sensor
response to a gas is described in this section. The theoretical study of the
phenomenological model described in Section 2 made it possible to propose
this method. The core of the method is the controlled periodic variation of
the gas composition in the atmosphere. It was theoretically demonstrated by
[4] that the oscillations of the gas coverage on the surfaces are determined by
the rate parameters of the chemical reaction. Since main characteristics of the oscillations can be evaluated within a few initial periods, the gas
detection time can significantly be reduced without a loss of the information.
The transition from the clean air signal to a saturated response to gas is
not required for the definition of the sensor output in the novel method. An
experimental implementation of the method is related to significant
modification of the existing equipment. Therefore, some essential aspects of
the methods are theoretically studied in present work.
The gas coverage on the surfaces is supposed as the key parameter in this
study. Such approach allows extending the findings of the study to various
types of the sensors. This is because the gas coverage on the surfaces
determines not only the functioning of the resistive gas sensors but also is
essential in any other types of the sensors in which the response depends on
the chemisorption of gas.
The key description of the oscillations of the gas coverage (4) was
derived within the phenomenological model supposing that the clean air is
replaced by an atmosphere in which an amount of a target gas is periodically
varied. According to (4), simple periodic variation of the gas concentration
in air (3) produces complicated oscillations of the gas coverage on the
surfaces of metal oxides. Two components are distinguished in these
oscillations. One of the components defines the oscillations of the coverage
with decreasing amplitude while another component represents oscillations
characterised by constant amplitude. The weight of the components depends
on the rate parameters of the surface chemical reaction.