Research of radiosonde humidity sensor with temperature compensation function and experimental verification

• A sandwich-plate capacitive humidity sensor, integrated with a snake-like platinum-resistance heater, was fabricated.
• Finite-element analysis method was used to obtain the temperature distribution of sensor surface when the sensor is heated.
• Comparison method is combined with capacitor charging and discharging method to measure humidity sensor capacitance.

In order to avoid radiosonde humidity sensor condensation and eliminate the humidity value influence due to board capacitance distribution in high-altitude environment, a sandwich-plate capacitive humidity sensor, integrated with a snake-like platinum-resistance heater, was designed. Finite-element analysis method was used to obtain the temperature distribution of sensor surface when the sensor is heated. Then, the function relationship between environment temperature and heating power was obtained. A measuring circuit was designed based on the humidity sensor characteristics and ground experiment results show that the humidity sensitivity is about 2.3RH%/pF, hysteresis is about 0.7%F·S, repeatability is about 1.9%, measurement uncertainty is about 4%, and time constant is about 0.5 s. Atmosphere aloft experiment results show that the humidity sensor which is described in the paper has good response time and desirable repeatability. Moreover, the condensation problem can be avoided effectively. The research results provide theoretical basis for carrying out comparison experiments.