Electrical Field-Enhanced Capacitive Transducers for Humidity and Moisture Control Systems

Humidity and moisture are difficult parameters to measure and control in greenhouses and in bulk stored grain. Greenhouse control systems with distributed sensors can manage dynamic environments to enhance crop yield, prevent disease, and conserve energy. Psychrometers are too complex for multi-zone climate control. At high levels of humidity, hygrometers have problems with accuracy, stability, and rapid response. Control systems with chemically resistant humidity sensors and condensation alarms can maintain optimum multi-zone climates for specific crops. Since the sensors measure moisture external to a low-moisture absorbing coverlayer, they can be used to control the moisture content of agricultural commodities and imported foodstuffs. Applications also exist in the grain drying, tempering, milling, and baking industries. Transducers were developed during Phase-I to measure humidity, moisture, and to anticipate condensation. Testing confirmed a unique capability to measure humidity in condensing environments and the moisture content of bulk stored grain. The sensors are resistant to harsh chemicals and insensitive to surface contamination. They will be optimized to reduce manufacturing costs using batch fabrication and calibration methods. Devices fabricated on small silicon chips will have an implanted temperature sensor.