Ultrasonic sensor

The ultrasonic sensor is a sensor, made available by LEGO Mindstorms, which can detect objects within a range of 5 to 255 cm. The sensor is shown in the picture below.

The sensor works as follows:

When the nearest object to the sensor is further than 255cm away, the sensor gives the maximum output '255'.

The distance from which the sensor first detects an approaching object depends on:

• The ultrasonic reflectance of the object, which is a function of the object's size and composition. The sensor detects large hard objects from a greater distance than small soft ones. For example, the sensor might detect a pane of glass at 255 cm and a hand puppet at 150 cm.
• The angle of incidence of the object relative to the sensor. The sensor detects objects directly in front of it at greater distances than objects off to the sides.

References

• [1] Ultrasonic Sensor Specifications and Use