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123 lines
2.8 KiB
C
123 lines
2.8 KiB
C
//
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// FILE: temperature.h
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// VERSION: 0.1.1
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// PURPOSE: temperature functions
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//
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// HISTORY:
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// 0.1.0 - 2015-03-29 initial version
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// 0.1.1 - 2017-07-26 double to float (issue #33)
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//
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#ifndef TEMPERATURE
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#define TEMPERATURE
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#include "WProgram.h"
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#define TEMPERATURE_VERSION "0.1.1"
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//Celsius to Fahrenheit conversion
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float Fahrenheit(float celsius)
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{
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return 1.8 * celsius + 32;
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}
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//Celsius to Kelvin conversion
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float Kelvin(float celsius)
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{
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return celsius + 273.15;
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}
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// dewPoint function NOAA
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// reference: http://wahiduddin.net/calc/density_algorithms.htm
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float dewPoint(float celsius, float humidity)
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{
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float A0= 373.15/(273.15 + celsius);
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float SUM = -7.90298*(A0-1);
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SUM += 5.02808 * log10(A0);
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SUM += -1.3816e-7 * (pow(10, (11.344*(1-1/A0)))-1) ;
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SUM += 8.1328e-3*(pow(10,(-3.49149*(A0-1)))-1) ;
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SUM += log10(1013.246);
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float VP = pow(10, SUM-3) * humidity;
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float T = log(VP/0.61078); // temp var
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return (241.88*T) / (17.558-T);
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}
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// delta max = 0.6544
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// 5x faster than dewPoint()
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// reference: http://en.wikipedia.org/wiki/Dew_point
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float dewPointFast(float celsius, float humidity)
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{
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float a = 17.271;
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float b = 237.7;
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float temp = (a * celsius) / (b + celsius) + log(humidity/100);
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float Td = (b * temp) / (a - temp);
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return Td;
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}
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// http://www.ccacac.com/wp-content/uploads/2010/06/Humidex-Graph.pdf -
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float humidex(float celsius, float DewPoint)
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{
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float e = 19.833625 - 5417.753 /(273.16 + DewPoint);
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float h = celsius + 3.3941 * exp(e) - 5.555;
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return h;
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}
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// TF = temp in F
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// R = humidity in %
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float heatIndex(float TF, float R)
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{
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const float c1 = -42.379;
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const float c2 = 2.04901523;
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const float c3 = 10.14333127;
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const float c4 = -0.22475541;
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const float c5 = -0.00683783;
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const float c6 = -0.05481717;
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const float c7 = 0.00122874;
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const float c8 = 0.00085282;
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const float c9 = -0.00000199;
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float A = (( c5 * TF) + c2) * TF + c1;
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float B = (((c7 * TF) + c4) * TF + c3) * R;
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float C = (((c9 * TF) + c8) * TF + c6) * R * R;
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return A + B + C;
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}
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// less constants => faster but slightly inaccurate
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// TF = temp in F
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// R = humidity in %
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float heatIndexFast(float TF, float R)
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{
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const float c1 = -42.379;
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const float c2 = 2.04901523;
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const float c3 = 10.14333127;
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const float c4 = -0.22475541;
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float A = c2 * TF + c1;
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float B = (c4 * TF + c3) * R;
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return A + B;
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}
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// integer version
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// TF = temp in F
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// R = humidity in %
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int heatIndexFastInt(int TF, int R)
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{
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// consts multiplied by 1024
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long c1 = -43396;
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long c2 = 2098;
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long c3 = 10387;
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long c4 = -230;
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long A = c2 * TF + c1; // so A is x 1024
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long B = (c4 * TF + c3) * R; // and B too
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return (A + B + 512) / 1024; // division becomes a shift; +512 is for rounding
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}
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#endif
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//
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// END OF FILE
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//
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