Thermal dewpoint sensing: A new approach for dewpoint detection and humidity sensing

This paper describes a novel approach to the detection of dew point temperature of water vapor in gases (air) based on a thermal principle. The core of the sensor is a silicon chip with a thin membrane (600times600times0.9 mum³) containing a heater as well as a thermopile for temperature detection. The membrane has a very low heat capacity and is cooled down with a Peltier-cooler located underneath the membrane. When the dew point of the surrounding water vapor is reached, water begins to condense on the membrane and changes its heat capacity. This change in heat capacity is detected by dynamically heating the membrane and recording its temperature response by using the thermopiles. Two different types of the sensor were developed and characterized. Based on a first configuration, dew point temperatures down to 45 K below ambient temperature can be measured with a maximum deviation of < 0.2 K. This configuration is optimized for the detection of residual moisture in technical gases. The second configuration was designed to measure dew point temperatures in the high humidity range of up to 100% relative humidity (RH) for climate control applications. It is able to measure the dew point temperature with a deviation of less than 0.5 K.