With designs consisting of a single ultrasonic

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Unformatted text preview: eans of ultrasonic barriers. Similarly it is possible to detect transparent, reflecting or jet black objects, where optical proximity sensors may fail. Even very thin transparent film of a thickness of approx. 0.01 mm can be detected head-on by means of ultrasonic proximity sensors. 7.3.4 Minimum possible distance of object As a proximity sensor requires a minimum processing time to detect the ultrasonic echo, it cannot operate within a certain blind area. In the case of short distances, "secondary lobes" of the ultrasonic sound cone can lead to error pulses. With designs consisting of a single ultrasonic transducer, completion of oscillation must be achieved after emission (see Fig. 7.1.2), before the echo pulse can be registered. © Festo Didactic GmbH & Co. KG • FP 1110 113 7. Ultrasonic proximity sensors 7.3.5 Position of object Similarly as with light, ultrasound is deflected on flat surfaces. In this case, an ultrasonic sensor does not receive an echo signal. Objects with smooth, even surfaces, can no longer be detected if the d...
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