read NDIR

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Joined: Tue Jul 23, 2019 10:47 am
Company: IBEC

read NDIR

Post by jburgues » Fri Oct 18, 2019 12:29 pm


In the readNDIR() function, the conversion to ppm is carried out in this line:

// conc(mV) --> concentración(% LEL)
conc = V_conc * sensor_config.m_conc;

Where m_conc 3.125 according to the calibration parameters stored inside the sensor:

Two questions arise:
1) Is the concentration in ppm (as indicated in the function header) or %LEL (as indicated in the comment above the formula shown above AND next to the sensitivity value)
2) Why do you multiply by the slope of the calibration instead of dividing by it (as in the rest of the sensors)?

Could you please clarify if the units displayed in the comments are correct or not.


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Joined: Mon Sep 28, 2009 1:06 pm

Re: read NDIR

Post by libelium-dev » Mon Oct 21, 2019 11:31 am


1) The concentration is in ppm. It's a typing mistake surely due to we copied/pasted the function readPellistorSensor to start to develop the readNDIR function and we forgot to change the comments.

2) There are 4 types of sensors and each one is read in a different way. In the case of the CO2 sensor, it's multiplied since the units of the sensitivity are ppm/mV.


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