Fast quartz resonant sensors for high humidity range 60–95% RH

Aiming at solving the problem of high-humidity measurement, an original humidity sensor is described. It is based on the resonant sensing principle. The sensor is composed of a quartz crystal and a Peltier module. Proactive approach is taken to produce condensation in the surface of the quartz crystal. The electrical parameters of the quartz crystal is changed due to dew condensation and then the resonant circuit stops oscillating. The time required until the circuit stops the oscillation is the dew condensation generated time and it is considered as a parameter evaluating humidity. The results show that relative humidity is detected as function of the time required until the oscillation stops and a good linear relationship in the range of 60–95% RH. It proved that the sensor is highly stable, sensitive, fast recovery and low-cost, and the response time and the dewetting time all less than 10 s.