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Non Contact Tachometer

Discussion in 'General Electronics Discussion' started by steve_venkat, Jun 28, 2017.

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  1. steve_venkat

    steve_venkat

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    May 22, 2017
    I'm trying to build an non-contact tachometer using PIC controller.
    For that I need to know how the beam is produced and what sensor they used from this image.I googled but i can't find the correct part name.Because every one using simple IR sensor to calculate the speed.Please help to find out the sensor or part.
     

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  2. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    The sign on he nozzle indicates a laser emitter and most likely a photodiode or phototransistor is used to detect the reflected light beam.
    It is even possible only an IR LED is being used and the laser sign is only an additional warning as you cannot see IR light.

    The mathematics behind the tachometer measurement is the same as for a simpel LED or IR-diode. You count the number of reflections per second and calculate the number of revolutions per minute from that measurement.
     
  3. shrtrnd

    shrtrnd

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    Jan 15, 2010
    What Harald Kapp said.
    The hand held unit you show produces an output signal, and also reads the reflected back-signal.
    I'm thinking when you talk about a 'sensor', you're wondering what your hand-held unit is counting(?)
    If that's what you mean by 'sensor', it is usually something on the shaft of the device you're trying to read the rpm of, which is whatever the hand-held device would see reflected back from the shaft. Typically a line of whatever type of scribe or paint that the hand-held device can see reflected back at it. Each time the shaft rotates one revolution, that
    reflective line on the shaft is counted by the hand-held device.
    Does that answer your question, or was Harald's explanation what you needed by itself?
     
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