Measuring humidity using a CO2 sensor

Discussion in 'Chemistry' started by iljoesjin, Oct 1, 2013.

  1. iljoesjin Registered Member

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    For my graduation project I am looking for a (cheap) sensor which measures CO2 and humidity and someone mentioned it might be possible to measure the CO2-level using only an humidity sensor by using the formula:

    C6H12O6 (glucose) + 6 O2 => 12 H2O + 6 CO2

    I am no chemic (nor a programmer), but I was wondering whether this would actually lead to usable values? And if it is also possible the other way around (measure H2O with a CO2-sensor)?

    The sensor will be used to measure indoor air quality and will provide tips for (manual) ventilation. I am a product designer so I will need to hire someone else to build this sensor for me, but before proceeding I was wondering about the above. Thanks in advance!
     
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  3. arauca Banned Banned

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    I suppose if you use Infrared band there is an absorption of water in air and there is a band on carbonyl for CO2 band . So it you select specific frequency for each gas or vapor you should be able to do it.
     
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  5. origin Trump is the best argument against a democracy. Valued Senior Member

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    That would work if your project has to do with the combustion of glucose. However, it sounds like you are trying to prove what the combustion products are for glucose in which case the measurements of the results are an important part of the poject.
     
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  7. exchemist Valued Senior Member

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    Humidity sensors: http://en.wikipedia.org/wiki/Hygrometer

    CO2 sensors: http://en.wikipedia.org/wiki/Carbon_dioxide_sensor

    From comparing these it is not apparent that there is any one type of device that can be used for both.

    Like Origin I'm mystified by the reference to the reaction you quote, which is that for the oxidation of glucose. I do not see how the fact that water and CO2 are the products of this reaction would lead anyone to think there might be a common means of detecting ambient levels of the two compounds. Surely for that you would need something that responds to the presence of these gases, not just something that generates them when burnt?
     
  8. arauca Banned Banned

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    OH absorption band at 3100---4000 / cm

    CO carbonyl " at 1750

    Are you saying you can not sence this to make a sensor ?
     
  9. exchemist Valued Senior Member

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    No, I'm saying I can read a Wiki article that (a) states humidity is difficult to measure accurately and (b) mentions IR nowhere among the recognised techniques for doing so.

    So it seems either you are the first person to think of it, or it has been thought of but does not work.

    You can draw your own conclusions.
     
  10. arauca Banned Banned

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    No sir I am not the first one , but without searching I thot it was a proper way . As per your challenge , I submit for you this commercial unit which uses IR band
     
  11. exchemist Valued Senior Member

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    Was there meant to be an attachment or a link?
     
  12. arauca Banned Banned

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  13. Captain Kremmen All aboard, me Hearties! Valued Senior Member

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    C6H12O6 (glucose) + 6 O2 => 12 H2O + 6 CO2

    If you burned the glucose in air, you would also get Carbon Monoxide, Carbon, and various Nitrogen Oxides.
    That formula looks like it is a simplified version of a reaction that takes place in plants.

    If you had a sensitive enough Ph indicator, you could measure the acidity of a fixed amount of boiled and cooled distilled water
    after shaking with a fixed volume of air. The CO2 would dissolve in the water to form carbonic acid.
     
  14. arauca Banned Banned

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    If you really want to analogize by wet method . you can burned in air and pass the volatile material into say 0.1 molar solution of KOH or NaOH and back titrate with 0.1 molar Hcl and establish the amount of CO2 you have produced based on the mass of the glucose , all oxygen does not come from the glucose
     

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