dew_point.cpp

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#include "dew_point.h"
 
#include <cmath>
 
namespace sensesp {
 
// dew point
 
DewPoint::DewPoint() : Transform<std::tuple<float, float>, float>() {}
 
void DewPoint::set(const std::tuple<float, float>& input) {
  // Dew point is calculated with Arden Buck Equation and Arden Buck valuation
  // sets For more info on the calculation see
  // https://en.wikipedia.org/wiki/Dew_point#Calculating_the_dew_point
 
  float const temp_celsius = std::get<0>(input) - 273.15;
  float const relative_humidity = std::get<1>(input);
 
  // valuation set for temperatures above 0°C
  float b = 17.368;
  float c = 238.88;
  const float d = 234.5;
 
  // valuation set for temperatures below 0°C
  if (temp_celsius < 0.0) {
    b = 17.966;
    c = 247.15;
  }
 
  float gamma =
      log(relative_humidity *
          exp((b - (temp_celsius / d)) * (temp_celsius / (c + temp_celsius))));
  float const dew_point = (c * gamma) / (b - gamma);
 
  this->emit(dew_point + 273.15);  // Kelvin is Celsius + 273.15
}
 
}  // namespace sensesp