| 摘要 |
A dew point sensor comprises a miniature capacitor (3) comprising insulated electrodes on the surface of a chip (1) on which water condenses between the capacitor plates, temperature sensor (4) adjacent to the capacitor (3), on the chip (1), a peltier cooler (2) arranged to cool the capacitor (3), and a microcontroller. The microcontroller is arranged to measure variations in capacitance from condensation and evaporation of water on and from the capacitor plates, to measure the temperature of the capacitor (3), and to control the peltier cooler (2) to maintain the temperature of the capacitor plates to around the measured dew point. In the preferred form the microcontroller is arranged to control the peltier cooler (2) to cool the capacitor (3) to below the dew point temperature, to allow the temperature of the capacitor (3) to increase until water is left predominantly at the edges of the capacitor fingers and to then determine the dew point by allowing the temperature of the capacitor (3) to increase towards the measured dew point at which the rates of condensation onto and evaporation from the fingers of the capacitor (3) are substantially equal. |
