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Alternate temperature dependence #6

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Alternate temperature dependence #6

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8ec0149
Update MQ135.cpp
balk77 Nov 17, 2016
fa69afe
Update MQ135.h
balk77 Nov 17, 2016
cd1206e
Update MQ135.cpp
balk77 Nov 17, 2016
65b7bcf
Update MQ135.h
balk77 Nov 17, 2016
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10 changes: 9 additions & 1 deletion MQ135.cpp
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Expand Up @@ -40,7 +40,15 @@ MQ135::MQ135(uint8_t pin) {
*/
/**************************************************************************/
float MQ135::getCorrectionFactor(float t, float h) {
return CORA * t * t - CORB * t + CORC - (h-33.)*CORD;
// Linearization of the temperature dependency curve under and above 20 degree C
// below 20degC: fact = a * t * t - b * t - (h - 33) * d
// above 20degC: fact = a * t + b * h + c
// this assumes a linear dependency on humidity
if(t < 20){
return CORA * t * t - CORB * t + CORC - (h-33.)*CORD;
} else {
return CORE * t + CORF * h + CORG;
}
}

/**************************************************************************/
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3 changes: 3 additions & 0 deletions MQ135.h
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Expand Up @@ -34,6 +34,9 @@ v1.0 - First release
#define CORB 0.02718
#define CORC 1.39538
#define CORD 0.0018
#define CORE -0.003333333
#define CORF -0.001923077
#define CORG 1.130128205

/// Atmospheric CO2 level for calibration purposes
#define ATMOCO2 397.13
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