Investigations of Rayleigh wave hydrogen sensors

A kind of hydrogen sensors based on Rayleigh wave devices is presented. Generally, the Rayleigh wave devices are covered by a sensitive layer, such as WO₃, to absorb hydrogen, which can be deposited by Sol-gel method or RF magnetron sputtering method. In the sensing experiment, frequency shift and/or insertion loss variation of the sensors exposed to H₂ with different concentrations are measured at room temperature. As the sensor is with the operating frequency of 120.5 MHz and insert loss of 26dB, about 64 kHz frequency shift and 1.8 dB insertion loss variation are observed for 2% H₂ in natural air.