Analysis of Mechanism of Dew Point Measurement Using a Colpitts Oscillation Circuit

Abstract

In this paper, based on the phenomenon that Colpitts oscillation circuit is hard to work when condensation occurs on the surface of the quartz crystal, a new dew point measurement device is developed, and it is mainly composed of a quartz crystal and a Peltier module. This measurement way is both rapid and reversible compared to the traditional methods. Wet sensitive characteristics of the quartz crystal, which is regarded as the humidity sensing element in Colpitts oscillator, is analyzed. The electrical parameters of the quartz crystal are changed due to proactive condensation, then vibration of oscillator will stop if the magnitude of the reactance of the quartz crystal is lower than the reactance threshold of the Colpitts circuit. Combining the theoretical analysis with experiment data, it indicates that the Colpitts circuit is feasible to measure dew point.