Sensor for gas analysis based on thermal conductivity, specific heat capacity and thermal diffusivity

We investigate a new method of gas analysis based on the determination of thermal conductivity, specific heat capacity and thermal diffusivity. A silicon micro-wire surrounded by the gas is supplied with transient heat power (sinusoidal or square wave signal). The induced transient changes in gas temperature are detected in several well defined distances from the heater. We demonstrate the detection of CO
₂
in N
₂
with a resolution of less than 1% within the physiological range of 0%-13%. The thermal diffusivity is determined with a failure of less than 5%.