Stable Heating Technology for Catalytic Combustion Hydrogen Gas Sensor Using Quartz Resonators

In this paper, we focus on heating technologies for gas sensors. To discuss the requirements of heating accuracy of the sensor quantitatively, the effect of temperature error on the sensitivity of the sensor was evaluated. A Au thin film was used as a catalytically inactive heater for the sensor. The design and fabrication of this novel sensor with a Au thin-film heater is discussed. To stabilize the properties of the heater, the effect of annealing on the resistivity and temperature coefficient of resistance of the heater at 120 degrees C was verified by experiment. Additionally, a heater control circuit using op-amps was designed. Using the controller, accurate heating with a temperature error within 0.16 degrees C was obtained. As a result, constant sensitivity in a hydrogen gas concentration range of 0-2 vol.% was provided, and the ability to detect a concentration of 0.01 vol.% was demonstrated.