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What is the difference between an Ultrasonic Sensor and a Distance Sensor?

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    An ultrasonic sensor is one type of distance sensor. – Gerben May 20 '17 at 16:39
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    What's the difference between a Ford and a Car...? – Majenko May 20 '17 at 17:30
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An ultrasonic sensor can usually develop and receive high frequency sound waves. They can be used to measure distance by measuring the time of flight of the sound wave.

distance(meters)  = [speed_of_sound(meters/second)][1] x time_of_flight(seconds)
distance(meters) = 343(meters/second) x time_of_flight(seconds)

For example, say the time of flight was 0.01 seconds.

distance(meters) = 343(meters/second) x 0.01(seconds)
distance = 3.43 meters

This is just one way distance can be measured by a processor. Other ways use different types of radiation such as electromagnetic radio and light radiation. Some of these use time of flight. Others use more exotic phase techniques. These types of detectors can be very accurate over long distances. But are usually very costly. They are commonly used for automated car driving.

A completely different approach uses triangulation or parallax of a light beam and a focused linear array light sensor.
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These types of detectors normally operate over short distances and are cheap to make. They are commonly used in places like copier machine to detect objects and paper. Or in automated vacuums cleaners to detect floor edges such as stair drop offs.

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A proximity sensor is a sensor able to detect the presence of nearby objects without any physical contact, see article proximity sensor.

In that article a lot of types are mentioned and ultrasonic sensors are one of them, so an ultrasonic is one of the types of distance sensors.

Types (copied from the above article):

  • Capacitive
  • Capacitive displacement sensor
  • Doppler effect (sensor based on effect)
  • Eddy-current
  • Inductive
  • Magnetic, including magnetic proximity fuse
  • Optical
    • Photocell (reflective)
    • Laser rangefinder
    • Passive (such as charge-coupled devices)
    • Passive thermal infrared
  • Radar
  • Reflection of ionising radiation
  • Sonar (typically active or passive)
  • Ultrasonic sensor (sonar which runs in air)
  • Fiber optics sensor
  • Hall effect sensor
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    You wrote: “A distance (or proximity) sensor uses a beam of electromagnetic radiation”. Not all of them do, and specifically, an ultrasonic sensor doesn't. – Edgar Bonet May 22 '17 at 8:16
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    I edit my answer, thanks for the improvement. – Michel Keijzers May 22 '17 at 8:26

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