sensors calibration ?

on http://docs.smartcitizen.me/#/start/how-do-i-calibrate-the-sensors there is no info :-o (
anouced temp is about 15°C real is about 20°C.....how to calibrate ?
Same for other sensor (sound, light, humidity.....)
Rgds

Comments

  • Understand that NOx and CO can not be calibrated, bur what about temperature?
    20 degrees C inside, but CitizenKit tells me its 15.
  • Nobody there ?
  • Hi @TechLabLR,

    On the SCK 1.1, the temperature and humidity are measured on the same chip sensor, the SHT21 by Sensirion. The datasheet says that it is pre-calibrated at the factory.

    When I check the JSON post for my SCK, the temperature reading is already in °C. I'm guessing the calculation is being made within the Smart Citizen database.

    Anyone else have an idea?

    -Matt
    SCK 685
  • I confirm Mine give almost °C under real value. If the sensor is really factory calibrated, as sending seem wrong then there must be only few issue directly on sck:
    1 / Chip are refurbished source ( bad, rejected by original manufacturer but sale by third party, this can append for some device with some uncontrolled supplier.....)
    2/ Chip have been solderer in a bad way (check for spec about this point)
    3/ Reading protocol is not good enough and give wrong value, there are some strict delay to respect for reading and so on.....)

    Any comment ?


  • @aitoraloa, do you know if there is a way to check the raw sensor data? Or is there another way to review/ manager the data? Thanks,

    -Matt
    SCK 685
  • @rohwer @TechLabLR Sorry for the late response. You can check the RAW sensor data via Arduino serial monitor. You can also send this RAW data from the SCK to your own server adding a customized formula. As we have said before, the formula in the platform is wrong! It was implemented thinking on a SCK v1.1 inside an enclosure. If you do not have your kit inside an enclosure you temperature will be always under real value. Any help on this aspect will be really welcome as we still trying to find somebody that focuses on calibration. If you are able to find the right formula, please... share it with us! Looking forward to hearing from you. Best. :)
  • edited September 2015
    Well, after some measurements... i found that my SCK (with no enclosure) gives (on average) a temperature -3,4 °C under the "real".

    Using the type for Traw conversion to Celsius, i created a function for a "corrected" Traw (as a function of the given by SCK) which will finally (after beeing used by the conversion type) give the real Celsius result.

    My question is:
    Where -in the code- should i add this type for my corrected Traw
    to be sure that the corrected Traw will be send to SC platform
    in place of the currently false Traw?

    Thanks in advance!
    (and my excuse for my poor english)
    dim

    PS. And, again for humidity, where -in the code- should i add a function for a "corrected Hraw"?



  • edited August 2016
    Hi. Is there someone in this community who knows how to calibrate the sensors? It is mentioned above that some sensors have been already calibrated, but the following article suggest to me that is not that simple:
    http://www.sciencedirect.com/science/article/pii/S092540051500355X

    Thank you for your help!

    Cheers, Marc
  • I'm curious about TechLabLR's post that didn't seem to get a response:
    I confirm Mine give almost °C under real value. If the sensor is really factory calibrated, as sending seem wrong then there must be only few issue directly on sck:
    1 / Chip are refurbished source ( bad, rejected by original manufacturer but sale by third party, this can append for some device with some uncontrolled supplier.....)
    2/ Chip have been solderer in a bad way (check for spec about this point)
    3/ Reading protocol is not good enough and give wrong value, there are some strict delay to respect for reading and so on.....)
    I get incorrect temperature and humidity readings when using the formulas in the SHT21 datasheet. aitoraloa says the formula on the platform is wrong. Isn't the formula given in the SHT21 datasheet? Anyway, it seems like a lot of folks get bad readings. And it seems silly that one would have to buy cheapo thermometers/hygrometers (that actually give correct readings) to "calibrate" the SHT21.

    I've looked at the code and it would seem that #3 above isn't the issue since Hold Master Mode is used. So what about #1 and #2? Most internet searching points to these being the issue with bad SHT21 readings.
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