Temperature and humidity compensated gas value

[tobiaspryning]

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.

[handytech · Accepted solution]

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.

[tobiaspryning]

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?

[o_o]

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.

[tobiaspryning]

Alright. Thanks for your help!