Development and Application of an Integrated Dew Point and Glass Temperature Sensor

With the optimization of HVAC system controls for comfort, air quality and energy efficiency the potential for fogging the glass has increased. To maintain occupant safety, a method to predict when such fogging conditions exist is necessary to be able to execute proactive control corrections to prevent fogging. Windshield fog conditions are predicated on windshield surface temperature, cabin relative humidity and the reference temperature of the humidity sensor. This has driven a joint development project between Delphi Automotive Systems divisions to develop an Integrated Dew Point and Glass Temperature (IDGT) sensor. This sensor is a combination of three elements: a glass temperature sensor, a relative humidity sensor, and a humidity reference temperature sensor. Using this sensor package, the cabin dew point is calculated from the relative humidity and humidity reference temperature for comparison with the windshield glass temperature. When the windshield glass temperature drops to or is below the cabin dew point temperature, fog will form on the windshield. Utilizing this information, a proactive automatic climate control system implements corrections before the occurrence of fogging.

This paper discusses the following issues concerning this new technology:

• Sensor design and development.
• A comparison between the existing technologies and the new sensor design.
• Vehicle / system integration of the sensor.