High Temperature Moisture Sensor

Discussion in 'The Projects Forum' started by stubbornTryHard, Jun 10, 2013.

  1. stubbornTryHard

    Thread Starter New Member

    Dec 19, 2012
    7
    0
    Hello,

    I am struggling to find a suitable sensor for my requirements, so though I'd throw it 'out there' to see if anyone has any ideas.

    So far, I have developed a wireless 'Pottery Kiln Temperature Logger', utilizing Arduino Pro Minis.
    This is great as a first 'serious' project for me, and seems to be working fine.

    However, one of the critical stages in firing such a kiln, revolves around knowing when all the excess water has been driven out of the clay.
    The old fashined way is to hold a small piece of mirror or a steel spoon over the vent .. and see how much condenstion is generated (it can be a lot!).

    Obviously it'd be nice if I could get this reading captured electronicaly along with my temperature readings.

    So, some critical points ...

    • The exhaust air coming out of the kiln when water is being driven off, will be at around 200 -250 degrees Celcius.
    • After the water has finshed, the exhaust gases will continue to rise up to 1100 degrees Celcius.
    Give the first statement, the sensore has to be operational at <=250 celcius.
    Given the second statment, I will have to either move the sensor out of the heat area after 200/250 Celcius, or if tolerant, leave it in place.


    Finally, may I just point out that this is a personal/hobby project ... I simply cannot justify £500 on an industrial unit.




    Well, that's me .... if anyone has any bright ideas ... I would of course love to hear rom you !




    Many Thanks
    Simon
     
  2. wayneh

    Expert

    Sep 9, 2010
    12,140
    3,054
    You might be able to build yourself a capacitance probe. Basically you set up an oscillator. The oscillation frequency depends on the capacitance of a probe placed in the test gas. Changes in humidity cause a shift in capacitance and thus oscillator frequency, which the electronics detect and display. Pretty tough for a DIY, IMHO, but maybe.

    Actually the condensation approach is pretty darn good. If you could control the temperature of the surface, and cool it until moisture forms, that gives a direct measurement of dew point and everything you need to know. As a simple test, you could hold the surface at a set temperature and use it as a visual pass/fail test. For instance, if no moisture condenses on a surface held at 80°C, go forward. This would be much easier to DIY.
     
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