Modelling of thermal processes in catalytic gas microsensors implementing a measurement of combustible gas concentration

Abstract

Thermal processes in catalytic gas microsensors consisting of the micromachined sensitive and reference elements are considered. The modelling procedure for determining the weighted mean temperatures in the elements of the microsensors is proposed. The 2D structure of each element is divided into the regions. The heat differential equation for the regions has the identical form and takes into account two ways of heat power generation: by heater and by catalytic layer. The specific heat power generated in the regions by the heater is determined from consideration of the processes in the Wheatstone bridge circuit with the catalytic gas microsensor. To find the specific heat power generated in the regions with the catalytic layer during oxidation of combustible gas the similarity theory is used. The temperature distribution in the regions is found by using the eigenfunction method and iteration procedure which allows the temperature dependencies of the parameters to take into account. For the catalytic gas microsensor implementing a measurement of methane concentration the following characteristics were determined: the output voltage of the bridge circuit with the catalytic gas microsensor as a function of the methane concentration in air; the dependencies of the weighted mean temperature of the micro-hotplate for each element and the heat power generated in elements on the methane concentration.