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A question about sensor

  1. Nov 18, 2008 #1
    Hi all,

    I have this sensor which monitors the moving of a steel bar (see attached pic). The green part is moving backward and forward (the arrows), the gray is stationary.
    What I would like to know is the principle of this sensor. At first I thought it uses a small led in the gray one and the green passing through will gives signal. But I can not see the led. It may be based on magnetism, but the two are made of plastics... and I am puzzled.

    Any input is appreciated.


    Attached Files:

  2. jcsd
  3. Nov 18, 2008 #2


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    Clarify something for me, please. You said initially that the thing measures the movement of a steel bar, then later that the parts are made of plastic. Do I take it, then, that the green bit is a plastic part that's attached to the steel?
  4. Nov 18, 2008 #3
    Yes, the green part is screwed to the steel bar that is moving.
  5. Nov 18, 2008 #4


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    Science Advisor
    Homework Helper

    It probably is an optical switch but uses an infrared led.
    The LED and photdiode will be inside the grey plastic. Thin plastic is fairly transparent to near IR and it will keep the optical parts clean.
  6. Nov 19, 2008 #5
    Thank you. I have checked and it's a photomicrosensor.
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