Need idea to develope h2 gas sensor circuit

Discussion in 'General Electronics Chat' started by rdevendrakumar1989, Aug 9, 2012.

  1. rdevendrakumar1989

    Thread Starter New Member

    Aug 9, 2012
    7
    0
    Hai Friends,

    Am decided to develope H2 gas sensor. Give me an idea to develope the circuits.I found there are 2 detection methods are there.. 1. Calorimetric Detection - Gas concentration Vs. Temperatutre Rise
    2. Conductivity Detection - Gas concentration Vs. Electrical conductivity Change.. Give me the idea
     
  2. ikalogic

    New Member

    Nov 26, 2004
    3
    0
    I think the second option is the way to go. I never done this before, but seems to me like a simple job for an opamp/comparator....
     
  3. rdevendrakumar1989

    Thread Starter New Member

    Aug 9, 2012
    7
    0
    Thank u for ur quick reply.. R u have an idea to develope the circuit
     
  4. MrChips

    Moderator

    Oct 2, 2009
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    3,357
    This is not for the easily intimidated.

    You need Electrical Conductivity.
    Also you need two sensors in a bridge configuration and a temperature sensor.
    The bridge output is non-linear and a function of temperature and every other gas. So you need to measure the other gases as well, especially CH4, CO2 and CO.
     
  5. wayneh

    Expert

    Sep 9, 2010
    12,093
    3,031
    Neither of the proposed methods is specific to hydrogen and simply won't work.

    You might be interested in reading this or this (see the section on detection).
     
  6. MrChips

    Moderator

    Oct 2, 2009
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    Not sure how you came to that conclusion. I have numerous H2 detectors working in the field.
     
  7. rdevendrakumar1989

    Thread Starter New Member

    Aug 9, 2012
    7
    0
    Hai Friends,
    We can sense H2 gas by two methods...
    1. Calorimetric Detection - Gas concentration Vs. Temperature Rise ( Produced by the heat reaction on a catalytic)
    Note : Its should be independent of coverage area for better response


    2. Conductivity Detection - Gas concentration Vs. Change in electical conductivity ( Reaction of gas on the solid surface)


    LEL of H2 is 4% .. so we cutoff the system before its reach that limit.. so 0- 80% LEL enough for us..



    Step :
    First purchase H2 sensor and make circuit for our own..



    Help :


    What are the h2 gas sensor suit for our requirement?
    Give an idea to create circuit..


    Thank You
     
  8. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,170
    395
    Figaro Engineering Inc is a good start. I was concerned about longevity as product required a heater; sample has been under test since 1972- guess it passes. Used TGS 109 for monitoring furnace room, check emissions of my old motor home, & as a fire detector, [it beat out a comercial smoke detector ]. Sensitivity of 109 about the same for H2 as propane.
     
  9. cork_ie

    Member

    Oct 8, 2011
    348
    58
    I would agree with Bernard - an existing sensor is the way to go. Figaro stuff is good and their H2 Sensor is likely a lot cheaper than anything you could possibly make. http://www.figarosensor.com/products/821pdf.pdf is specifically designed for H2 and has good sensitivity and ability to discriminate from other gases.
    Price from RS http://radionics.rs-online.com/web/p/gas-detection/5390005/ in Europe is €68-00 for 1 and €61-00 for 15+ units , RS are not noted for being the lowest priced supplier of anything and there is a good chance you will find them cheaper elsewhere.
    Of course that is only the bare sensor you will have to build a circuit around it to provide the heater supply and display/record the H2 value.

    I am sure that if the 821 sensor suits your needs that some good people here will help you with the external electronics
     
    Last edited: Aug 11, 2012
  10. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,170
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    Are you looking for a sound- light alarm, relay closure, or meter reading, on given concentration? I used a PUT & SCR for a latching alarm, & comparator & relay for another. Used a time delay for heater warmup.
     
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