METHOD AND APPARATUS FOR ACCURATELY MEASURING THE DISTANCE TO A SURFACE

摘要

The device relates to measuring the distance (G) to a surface (S) of an object using ultrasonic energy pulses. An ultrasonic energy pulse (35,36) is directed toward the object and the time is measured for the reflection to return so as to determine the distance (G) to the object. A reference ultrasonic pulse (37,38) is directed through a fixed and known distance to provide a reference measurement. To enhance the accuracy of the measurement, the air in the region traversed by the ultrasonic pulses is mixed by directing a swirling flow of air (73) in this region so that the temperature of the air in the path of the reference measurement is more nearly representative of the temperature of the air where the distance measurement is taken.