AC characterisation of thermal flow sensor with fluid characterisation feature

We have investigated the determination of flow speed and simultaneously gas concentration in a binary gas mixture. The fabrication process and characterization of a sensor element, based on the thermal principle, is presented in this paper. The sensor is equipped with an unsymmetrical 1D-array of temperature sensors and a heater. Time modulated heating is used to extract flow speed from thermal gas properties. Phase shift determines the thermal conductivity of the gas mixture. The accurate flow velocity can be calculated from amplitude measurement afterwards. Thermal conductivity can be already determined with an accuracy of 90%.