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Near field (~D /λ) (1) 2 Far field (2) Fig. 16.6.1: Sound emission characteristic of an ultrasonic proximity sensor 266 © Festo Didactic GmbH & Co. KG • FP 1110 16. Solutions Exercise 7.2 Deflection of ultra-sonic sound waves
Because the same principle applies for ultrasonic waves as for light beams, i.e. the
angle of incidence equals the angle of reflection, a deflection of ultrasonic waves by
90° is possible.
The reflector must be carefully adjusted. As deflection causes dissipation, multiple
deflection should be avoided. Exercise 7.3 Sensing of boxes on a conveyor belt
The device used (range 20 – 100 cm) is adjusted in such a way that it just fails to
detect the base of an empty box. In this way, a signal is generated when a filled box
passes. The signal is independent of the height of the box or the filling level. The
presence of a box is signalled by means of a short signal as the sound cone passes
through the side of the box. 16.7
Solutions to exercises
from Chapter 8 Exercise 8.1 Range of air ba...
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- Spring '12