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Testing CO gas sensor — Parallax Forums

Testing CO gas sensor

emmettpatton_nscc2013emmettpatton_nscc2013 Posts: 9
edited 2013-01-14 10:56 in Accessories
I was wondering if there is any thing I can use to test the CO sensor in a classroom setting, using something like a canned air. We're trying to avoid lighting anything on fire to test it.

Comments

  • FranklinFranklin Posts: 4,747
    edited 2013-01-04 07:55
    From the documentation:
    The use of a standard butane hair curler is an easy, safe source to use for a very low carbon monoxide (CO) gas concentration (less than 500 ppm) and can be used during calibration and testing of the CO Gas Sensor Module.
  • Tracy AllenTracy Allen Posts: 6,658
    edited 2013-01-04 14:02
    There is a method to produce milliliter quantities of near 95% pure CO using reaction of concentrated sulfuric acid with formic acid:
    http://mattson.creighton.edu/CO/
    The whole process is chemically dangerous, as noted in the article! :tongue: The article goes on to present an informative series of experiments that can be performed with the resulting syringe full of CO.
  • D.PD.P Posts: 790
    edited 2013-01-06 18:02
    Tracy Allen wrote: »
    There is a method to produce milliliter quantities of near 95% pure CO using reaction of concentrated sulfuric acid with formic acid:
    http://mattson.creighton.edu/CO/
    The whole process is chemically dangerous, as noted in the article! :tongue: The article goes on to present an informative series of experiments that can be performed with the resulting syringe full of CO.

    Thanks for this link Tracy.
  • emmettpatton_nscc2013emmettpatton_nscc2013 Posts: 9
    edited 2013-01-07 07:21
    thanks for the help guys, i think we'll stick to the hair curler haha, im not to confident in my chemistry skills to try the mixture in class :tongue:
    thanks again
  • Tracy AllenTracy Allen Posts: 6,658
    edited 2013-01-07 09:29
    That site at creighton.edu is fascinating, even if you can't use the CO reaction. Lots of what they call "microscale gas chemistry", with explorations and great explanations of everyday and lesser known phenomena that should be of interest for the educator at the high school or college level. I guess you saw some of that David? We can even generate some CO2 for better calibrations!
  • ElectricAyeElectricAye Posts: 4,561
    edited 2013-01-07 12:24
    Tracy Allen wrote: »
    That site at creighton.edu is fascinating, even if you can't use the CO reaction....!

    Very interesting, especially the microwave methods they link to. Thanks!
  • ercoerco Posts: 20,255
    edited 2013-01-07 17:15
    Car exhaust, obviously. You could easily "fill" a tupperware container or 2-liter bottle and carry that indoors. Better yet...

    I live in smoggy LA. I bet our fine city would make you a smoking deal on boxcars full of CO. Just say the word and I'll have my people call your people. :)
  • Tracy AllenTracy Allen Posts: 6,658
    edited 2013-01-08 15:15
    Erco, good deal, we need it, set up the call. You know, everybody up here drives a Prius or a Leaf.
  • ercoerco Posts: 20,255
    edited 2013-01-09 09:16
    @Tracy: Who you talking to? :) I'm convinced there are more Priuses per mile in SoCal than anywhere. Toyota US HQ is in my backyard. I count Priuses when I run. I often see 10-15 per mile. At stoplights, I'm surrounded by Priuses. They're taking over!

    Leafs are increasing, they now lease for $199/month, and we have free recharging at work. Worth considering.

    One of our bigwigs here has a Fisker Karma. Sleek, but a complete embarassment WRT cost, reliability, and efficiency.

    Of course, giant gas-burning SUVs and Hummers still outnumber them 100 to 1... so let's make a deal on some smog!
  • emmettpatton_nscc2013emmettpatton_nscc2013 Posts: 9
    edited 2013-01-10 08:27
    can i have 3 bottles by monday? ;)
  • emmettpatton_nscc2013emmettpatton_nscc2013 Posts: 9
    edited 2013-01-10 08:32
    we're having a hell of a time getting the right reading from this sensor. we re-created the board since we only have the sensor and we are getting a minimum voltage reading of 2.10 v on test points 1 and 2. The documentation says to set it to 0.8v on TP1 and 2 but we cannot reach that. I am wondering if there is a diffrerent and more easier way to hook the sensor up to the basic stamp and get a reading.
  • Tracy AllenTracy Allen Posts: 6,658
    edited 2013-01-12 15:41
    Those calibration results do not make sense. Those voltages both come from variable resistors that have one end attached to ground, so in both cases it should be possible to turn them all the way down to zero. It or the meter must be hooked up wrong. Here is the schematic from the product page.

    Parallax_CO.png

    See TP1 and TP3 in relation to R3 and R4.

    The product page says "out of stock" and "replacement coming before Christmas 2012". We may be able to set up our LA vs SF smog-off any day now!
    Parallax_CO.png
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  • 4x5n4x5n Posts: 745
    edited 2013-01-12 16:23
    Should be able to buy a small tank of calibration gas for a reasonable price. I worked in an engine lab (we tested fuel and oil additives in test engines) and know that cylinders of various calibration gases are cheap but don't know how small of a tank you can get. Who wants a four foot tall tank of CO in their garage.

    Keep in mind that as of the late 90s the various gas sensors (including CO) needed to be calibrated prior to each use.
  • Igor_RastIgor_Rast Posts: 357
    edited 2013-01-12 18:35
    I would say , If you want a reading that makes some sense at all , try bying a K-30 co2 sensor , just a uart connection
    4 wires ( RX, TX, GND + Vcc ), ask for the reading , get the reading . and its accurate for a reasonable cost

    have spend allot of time myself trying to get a usefull reading out of those taguchi sensors ,(picture of proof :smile: )
    2013-01-13 03.26.49.jpg

    At a point I just had enough , Anyway Good Luck . Maybe Its helpfull
    2013-01-13 03.26.49.jpg
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  • Tracy AllenTracy Allen Posts: 6,658
    edited 2013-01-13 14:30
    Igor, the OP is looking to detect monoxide, not dioxide. I don't know of any NDIR CO detectors, and wonder why such a thing is not more common. I know what you mean about stability (lack thereof) of the catalytic sensors.

    Household CO sensors use electrolytic fuel cells, but they too have long term stability problems. The four-electrode cells from AlphaSense appear to take that approach to a higher level of sensitivity and stablilty. They are considerably more expensive than the catalytic sensors, but on a par with NDIR. Low power consumption, much lower than NDIR, and much much lower than catalytic types. I'm working with a group that is evaluating them.
  • emmettpatton_nscc2013emmettpatton_nscc2013 Posts: 9
    edited 2013-01-14 10:09
    discovered the problem for the bad voltage readings, we recreated the circuit with two single op-amp IC's and therefore did not have the common voltage points required. switched the two IC's out for a dual op amp and the readings are making more sense. how ever we have tried the calibration with a can of span gas and also lighting a lighter, still no trip :( going out to get some exhaust from my car right now and see if it will work.
  • ElectricAyeElectricAye Posts: 4,561
    edited 2013-01-14 10:56
    emmettpatton_nscc2013 wrote: »
    ... going out to get some exhaust from my car right now and see if it will work.

    Hope you're not doing it inside a garage. It only takes about 9 minutes for the average garage to build up lethal levels. Make sure you've got LOTS of ventilation.

    CO+poisoning.jpg
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