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    Temperature and humidity compensated gas value


    Temperature and humidity compensated gas value

    In this post in the knowledge-base the value "sensor compensated gas resistance" is specified and described as follows:

    "The sensor compensated gas resistance provides the gas resistance compensated by temperature and humidity influences"

    However looking at the code(bsec_datatypes.h, line 298) as well as the BSEC integration guide(page 45, top) "BSEC_OUTPUT_COMPENSATED_GAS" is described as " reserved internal debug output" (page 45, top).

    Reading the value from the BSEC library gives an odd value (6.34 Ohm when raw_gas is 369129.03 Ohm), and its accuracy is always 0.


    I would very much like the compensated value, and hope someone can help me get it. 

    Thanks in advance.

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    4 REPLIES 4
    Community Moderator

    Re: Temperature and humidity compensated gas value

    Thank-you for you feedback, there seems to be indeed some mistakes in the documentation that have now been reported.

    Regarding the outputs:

    • since the compensated gas output is another representation for the gas resistance signal, there is no specified accuracy indicator,
    • the compensated gas output is not given in Ohm units but in log10 scaled format, therefore you could try 10^comp_gas_value.

    Re: Temperature and humidity compensated gas value

    Good to know. Then either the library should be updated to return the value in Ohm, or the unit should be changed in the output explaination.

    Calculating 10^comp_gas_value gives a value much higher than the un-compensated.

    raw_gas: 224,186 Ohm
    compensated_gas: 10^(6.167286)=1,469,893.9 Ohm

    humidity: 45.850
    compensated_humidity: 45.618
    pressure: 100,784.844 
    raw_temperature:  27.790
    compensated_temperature: 27.725

    Can anyone with a bit more experience with compensated gas resistance values tell me if that seems right?

    Community Moderator
    Community Moderator

    Re: Temperature and humidity compensated gas value

    That sounds reasonable, especially at 45% humidity. Humidity lowers the resistance value quite a bit.

    The idea of providing this output, is for our customers to use our characterized temperature and humidity compensation, but develop their own algorithms instead of the "Indoor Air Quality" algorithm.

    Re: Temperature and humidity compensated gas value

    Alright. Thanks for your help!