Influences of humidity on the preamp of the pressure sensor using a temperature-stable quartz oscillator

The influence of relative humidity on the preamp of a quartz-oscillator pressure sensor was investigated because temperature affects the output from the pressure sensor not only through the quartz oscillator but also through the preamp. The pressure sensor used in this study consists of a quartz oscillator, the output of which is less affected by temperature, and a preamp. The relative humidity dependence of the preamp was obtained by varying humidity at the preamp, while keeping humidity at the quartz oscillator constant. It was found that the fluctuation of the output from the pressure sensor at 10, 20, 30, 40, and 50°Cwas below 0.16% of the average output at maximum, which is smaller than the minimum detection level when used for hydrogen sensing. These results confirm that the relative humidity does not significantly affect the output through the preamp of the quartz-oscillator pressure sensor.