Unformatted text preview: eviation is for instance more than
±3° – ±5° of the vertical alignment to the proximity sensor. With objects of a rough or
irregular surface a wider angle is possible, whereby the ultrasonic wave length, the
surface finish and distance are also relevant. 3° - 5° 3° - 5° 45° 1 2
3° Sand (1) Liquid (2) Fig. 7.3.2: Effect of the object surface when using ultrasonic sensors 114 © Festo Didactic GmbH & Co. KG • FP 1110 7. Ultrasonic proximity sensors 7.3.6 Effect of ambient temperature, humidity, air pressure
Ultrasonic speed depends on air temperature by approximately 1,8 ‰ per °C.
Because ultrasonic proximity sensors are invariably not temperature compensated,
a slight change in switching point may occur as a result of ambient temperature. The
humidity content of air at a temperature range below 40 °C effects a maximum
change in the speed of sound by 1.4 % between a relative air humidity of 0 % and
100 %. Natural changes in atmospheric air pressure do not cause any significant
changes in the speed of sound. Only at high altitudes does the speed of sound
decrease slightly. 7.3.7 Diverting the u...
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This note was uploaded on 11/01/2012 for the course CHEMICAL 102 taught by Professor Jamesrodriguez during the Spring '12 term at Universidad Politécnica de Cartagena.
- Spring '12