A PULSED ULTRASONIC DISTANCE MEASUREMENT SYSTEM BASED UPON PHASE DIGITIZING

A pulsed ultrasonic distance measurement system (UDMS) for use in air is described. A new method of timing is presented that is based upon the transmission of a binary-frequency shift-keyed (BFSK) signal followed by data acquisition and signal processing of phase-digitized information from the received signal. The method reduces many of the problems that arise when dealing with the nonideal behavior of ultrasonic transducers. One of the major advantages is the ease with which the method may be implemented while maintaining high accuracy, since amplitude sampling is not required. Comparison with common ranging techniques is presented, which shows the inherent noise immunity of the new method. A test setup is described, and results given, demonstrating the underlying principle and accuracy. The system measures. distances of up to 5000 mm with an accuracy of +/-1 mm.