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Ultrasonic Sensor
The Ultrasonic Sensor is a digital sensor that can measure the 
distance to an object in front of it. It does this by sending out high-
frequency sound waves and measuring how long it takes the sound 
to reflect back to the sensor. The sound frequency is too high for 
you to hear.
Distance to an object can be measured in either inches or 
centimetres. This allows you to program your robot to stop a certain 
distance from a wall.
When using centimetre units, the detectable distance is between 3 
and 250 centimetres (with an accuracy of +/- 1 centimetres). When 
using inch units, the measurable distance is between 1 and 99 
inches (with an accuracy of +/- 0.394 inches). A value of 255 
centimetres or 100 inches means the sensor is not able to detect 
any object in front of it.
A steady light around the sensor eyes tells you that the sensor is in 
Measure Mode. A blinking light tells you that it is in Presence Mode.
In Presence Mode, this sensor can detect another Ultrasonic Sensor 
operating nearby. When listening for presence, the sensor detects 
sound signals but does not send them.
The Ultrasonic Sensor can help your robots avoid furniture, track a 
moving target, detect an intruder in your room, or ‘ping’ with 
increasing volume or frequency as an object gets closer to the sensor.
For more information, see Using the Ultrasonic Sensor in the EV3 
Software Help.
EV3 Sensors
Ultrasonic Sensor
Detectable distance
NOTE:
Since the Ultrasonic Sensor 
depends on reflection of the sound 
waves it may be ineffective at detecting 
surfaces that are textured or objects that 
are rounded. It is also possible for 
an object to be too small for the 
Ultrasonic Sensor to detect it.
EV3 TECHNOLOGY