Michel F. Sultan

Ultrasonic Air Temperature Sensing for Automatic Climate Control - Vehicle Test

An ultrasonic air temperature sensor, intended to help improve automatic climate control (ACC), has been demonstrated in a vehicle. Ideally, ACC should be based on inputs correlated with thermal comfort. Current ACC systems do not measure the air temperature best correlated to thermal comfort — at breath level in front of an occupant. This limits the thermal comfort that ACC can provide under transient conditions. An ultrasonic sensor measures the bulk air temperature, is transparent to the driver, and can use commercially available components. In a proof-ofconcept test, we monitored the thermal transients in a vehicle during cool-down after a hot soak and also during warm-up after a cold soak. The ultrasonic path was along the roof console. The ultrasonic temperature always agreed to ±1 oC with the air temperature measured by a thermocouple at the midpoint of the ultrasonic path. Compared to breath-level temperature, there was good agreement for the winter test but, for the summer test there was a 5 oC constant shift. Thermocouple data taken at the two locations showed the same effect. The ultrasonic sensor is rapid and precise, and it is a good candidate for improving ACC.

Ultrasonic Air Temperature Sensing for Automatic Climate Control - Sensor Development

Automatic climate control could be improved by measuring air temperature ultrasonically. Thermal comfort correlates better with bulk air temperature than with the temperature measured by the in-car sensor. The time of flight of an ultrasonic pulse through the air gives the bulk air temperature. In a proof-of-concept experiment, it is accurate to ′ 0.5 °C from -40 to +60 °C. Two operational modes are demonstrated: pulse-echo in which a single transducer creates a pulse and detects its return from a reflector, and single-pass in which a source transducer creates a pulse that travels directly to a separate transducer.