How to detect water vapor inside plastic tube

Discussion in 'Electronics Resources' started by eoinclancy1, Jul 15, 2017.

  1. eoinclancy1

    Thread Starter New Member

    Jul 14, 2017
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    Hi Guys,

    Anyone have any experience in attempting to detect the presence of or amount of liquid vapour flowing through a (plastic) tube?
    The vapour is basically a fine particle mist that will flow through the tubing and I can't find any sensors that are dedicated to this purpose. Some sensors use proximity sensors to detect the presence of gas bubbles or just to detect liquid flow.

    Any advice regarding what sensors would be applicable to this purpose would be greatly appreciated.

    (I have done some research into infrared, proximity and humidity so far - nothing promising yet)
     
  2. #12

    Expert

    Nov 30, 2010
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    Merely the presence?
    It must be moving or the particles would fall out of the air stream.
    Got anything on velocity, pressure, or temperature?
    Does it have to be a plastic tube? Is the mixture allowed to go into a chamber and then resume its flow in another piece of tubing?

    In other words, what are you trying to accomplish. This might not even be the best method.
    Better questions get better answers.
     
  3. MrChips

    Moderator

    Oct 2, 2009
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    Have you tried an opto-interrupter?
     
  4. eoinclancy1

    Thread Starter New Member

    Jul 14, 2017
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    The vapour particles will be moving with the aid of a ventilator from which it would be possible to calculate the velocity (l/min) and probably the pressure too. The tube will always be see-through plastic and the flow will not be flowing into a chamber. It will just flow past the 'sensor', get to its destination, and then flow in a different direction.
     
  5. eoinclancy1

    Thread Starter New Member

    Jul 14, 2017
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    The opto-interrupter looks very interesting, thanks!!
    Have you ever seen it used for a similar purpose? Is it based on infrared? And lastly, would it work through the plastic tubing if the distance between emitter and receiver was ~1"?
     
  6. #12

    Expert

    Nov 30, 2010
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    I worked with chemical analysis by color comparison in visible light through various colors of filter in 1972. That was clear tubing, but the colors were very important!
     
  7. eoinclancy1

    Thread Starter New Member

    Jul 14, 2017
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    Hmmm interesting.
    Do you an infrared sensor with an analogue output would give any useful feedback if used on either side of the plume?
     
  8. #12

    Expert

    Nov 30, 2010
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    The stuff I calibrated in 1972 created an analog output, but whether you should use infra-red?
    That's what chemists do. I do analog design.
     
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  9. MrChips

    Moderator

    Oct 2, 2009
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    You can get opto-interrupters for IR range. Plastics and glass tend to be opaque to IR. You want to use quartz glass tubing for IR.
     
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  10. #12

    Expert

    Nov 30, 2010
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    I predict a negotiation on this point.
     
  11. atferrari

    AAC Fanatic!

    Jan 6, 2004
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    The only mist detector I met ever (in the carter of a fast marine engine) measured the level of light which was more or less obscured by the oil mist. BTW, ignoring the associated alarm costed around 1.000.000 USD in crankshaft replacement.
     
  12. muhzd

    Active Member

    May 25, 2009
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    Vibration?Histle?
     
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