| 摘要 |
<p>Described is ultrasonic distance-measuring equipment in which an emitter generates a signal in the form of a pulse which is reflected and converted by a receiver into an electrical echo signal. By measuring the travel time between emission and reception of the signal, the distance separating the emitter and receiver is determined. Since the intensity of the echo signal relative to that of the emitted signal depends on the nature of the reflector and the distance separating the emitter and receiver, inaccuracies can occur in the analysis of the echo signal. These are avoided by changing a switching threshold or by changing the echo-signal amplification, or by modifying the emitted signal as a function of the previously received echo signal.</p> |
