Ask a Mechanical Engineer: Motion Sensor Work Underwater?

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Discussion Overview

The discussion revolves around the feasibility of making motion sensors work underwater, exploring various technologies and considerations related to their functionality in aquatic environments.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant inquires about the possibility of underwater motion sensors and expresses uncertainty about water interference.
  • Another participant suggests that a combination of a video camera and software could be used to detect motion underwater, although notes that light conditions may limit effectiveness at greater depths.
  • A participant mentions Doppler shift flow meters as a related technology that measures the velocity of bubbles or particles in fluids.
  • It is noted that existing underwater motion sensors operate based on Doppler shift, contrasting with typical infrared motion sensors.
  • Questions are raised regarding the specifics of the water movement, required range, and size of moving targets, indicating that these factors could influence sensor performance.
  • Discussion includes the impact of environmental conditions, such as waves producing variable Doppler shifts versus a flowing river producing a constant shift.
  • The role of ultrasonic pulses or chirps is mentioned, with emphasis on how changes in echo can indicate changes in the environment.

Areas of Agreement / Disagreement

Participants express varying views on the technologies and conditions that affect underwater motion sensing, indicating that multiple competing perspectives remain without a clear consensus.

Contextual Notes

Participants highlight limitations such as the dependence on environmental factors, the impact of light at different depths, and the specific requirements for motion detection, which remain unresolved.

Mark14
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I was looking to get any advice from a mechanical engineer about motion sensors. Would it be possible to make a motion sensor work underwater? i wasn't sure if the water would interfere. Thanks for anything, if this isn't an appropriate place for this question i would appreciate if anyone has a better forum to ask on. Thanks!
 
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I'm not an ME and I don't know about different kinds of motion sensors but I can guarantee you that you can make an underwater motion detector with a combination of a video camera and software to detect changes in the image. This obviously would not work as the light got dimmer and dimmer at depths.
 
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Doppler shift flow meters are one example of similar tech. They measure the velocity of bubbles or particles in fluids.
 
Yes there are underwater motion sensors. Like Billy said, their functioning is based on Doppler shift. Usual motion sensors use infra red.
 
How is the water moving? What range do you require? How big are your moving targets?

Waves would produce variable doppler shifts, a flowing river would produce a constant doppler shift.

The echo of an ultrasonic pulse or chirp will depend on the position of nearby objects. If the record changes then the environment has changed.
 

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