An Acoustothermic Hydrogen Sensor

It has been revealed in experiments that, based on the thermal influence of gases on the surface acoustic wave propagating in a hot acoustic transmission line, it is possible to efficiently detection hydrogen without using gas-sensible coatings. It order to increase the sensitivity, the acoustic transmission line of the sensor is made of a piezoelectric crystal of В12SiO20 with large temperature coefficient of delay and the total phase shift and delay of the wave between radiating and receiving transducers are increased owing to propagation of this wave through two cylindrical roundings. When concentrations are in a range of 0.1–3.2%, the acoustothermic response to hydrogen by an order of magnitude exceeds responses to O2, CH4, NO, and water vapor of the same concentrations. Owing to the absence of a gas-sensible coating, the long-term stability of detection is high and is less than ±2% during six months.