QCM sensor coated by a sensing film has been studied as a gas-sensing device with high gas selectivity and high sensor sensitivity. One of the problems to be solved for practical applications is that a resonance frequency of QCM sensor drifts due to the influence of humidity. In this study, we investigated a compensation method of the humidity drift of QCM sensor for NH3 gas by using the element coated by the reference film, that was prepared by modifying the phosphate group of zirconium phosphate of the sensing film with sodium hydroxide. The response properties of the reference element were measured. The results showed good agreement with the humidity response of the sensor element without reacting to ammonia gas. It was found that the compensation of the humidity drift was successfully accomplished by calculating the frequency difference between the sensor element and the reference element. The application to small QCM (1.3×0.9 mm) was also presented.
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