Home Forum Support A3: CO2 not adjusting for temp ?

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  • #28847
    quincyfive
    Participant

    Our A3 is giving what appears to be quite erroneous data. This was on the lowest bench of a sauna that doesn’t get above 60°c and comparing to a GasLab 501. We also had two other CO2 sensors nearby with readings nearly identical to the 501. There appear to be two problems; 1) The A3 is reading high with average room temps and 2) is not adjusting for temp changes.

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    #28851
    quincyfive
    Participant

    Here’s a cleaner example with humans. Just a warm up and cool down. CO2 should not have changed.

    #28852
    quincyfive
    Participant

    Let’s try this again… A cleaner example WITHOUT humans.

    #28887
    quincyfive
    Participant

    A response to this would be appreciated. This is a serious issue that calls in to question the accuracy of all uRAD products.

    #28888
    Wolferl
    Moderator

    Hi Quincy,

    CO2 concentration /is/ dependent on air temperature, have a look at this paper.
    Also, the CO2 sensors used (Winsen MH-Z19) are not very accurate, the datasheet states +/- 50ppm + 5% of reading.
    The datasheet also states that the reading is “temperature compensated”…one never knows how good that works inside a device that generates additional heat.
    It is a cheap sensor after all and one cannot expect laboratory-grade precision from them.
    Additionally, that sensor performs some magic self calibration (that could explain the sudden drop to 450 ppm) and can also be calibrated by the MCU.

    HTH & Cheers,
    Wolferl

    #28889
    quincyfive
    Participant

    Wolferl, that is not acceptable. Our Gaslab 501, IQ Air Visual Pro ($239) and AWAIR Element ($149) all provide accurate CO2 readings that are in agreement with each other and that properly compensate for temp changes. Your readings are off by multiple 100’s of PPM, not just 50 or 5%. Your device costs 2x to 4x more than these others, it should be better, not worse.

    “…one never knows” – YOU should know. You are the manufacturer.

    “that sensor performs some magic self calibration”. Some magic? You are the manufacturer of a device that you are selling. You should fully understand exactly what your vendors are doing. Others who use this same sensor are getting accurate results from it, why are you not?

    #28890
    Wolferl
    Moderator

    Hi Quincy,

    No need to be rude here, dude. I am /not/ the manufacturer, I’m just a customer like you are. I just wanted to point out how this system works.
    If you are not happy with its performance, talk to Radu.

    Cheers and EOD for me,
    Wolferl

    #28891
    quincyfive
    Participant

    Apologies @Wolferl. You are listed as Mod and I assumed that you work for Radu.

    “If you are not happy with its performance, talk to Radu.” – Exactly why I posted in the support forum that he normally frequents. This is beyond my individual happiness with this device as it calls in to question the accuracy of every device made by uRAD.

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