Math formula required

From a Temp and Humidity sensor readings can anyone give me the mathematical formula for converting to" Temp and Humidity" to "Dew Point".
I would like to display

Temperature Humidity Dew Point

Tx

Hello Farticus

Take a look here to acquire the knowledge:

1 Like

From post #2 @paulpaulson , the Formula for Dew point is (Fig-1):
dewPointFormula
Figure-1:

Sketch:

char myData[20];

void setup()
{
  Serial.begin(9600);
}

void loop()
{
  Serial.println("Enter Temperature and Humidity as: TT.TT,HH.HH");
  while (Serial.available() == 0)
  {
    ;
  }
  byte m = Serial.readBytesUntil('\n', myData, sizeof(myData) - 1);
  myData[m] = '\0';
  //Serial.println(myData); //debugg
  char *token;
  token = strtok(myData, ",");
  float ttF = atof(token);
  //Serial.print(ttF, 2); Serial.print(' '); //debugg
  //------------------------
  token = strtok(NULL, ",");
  float hhF = atof(token);
  //Serial.println(hhF, 2); Serial.println(); //debugg
  //----------------------
  float dewPoint = calculateDewPoint(ttF, hhF);
  Serial.print("Dew point: "); Serial.print(dewPoint, 2); Serial.println(" degC");
  Serial.println();
}

float calculateDewPoint(float T, float RH)
{
  float b = 243.12;
  float a = 17.625;
  float y1 = log(RH / 100.00);  //-0.58
  float y2 = (a * T) / (b + T); //
  float dP = (b * (y1 + y2)) / (a - (y1 + y2));
  return (dP);
}

Output:

Enter Temperature and Humidity as (TT.TT, HH.HH): 34.50, 56.75
Dew point: 24.67 degC

Enter Temperature and Humidity as (TT.TT, HH.HH): 45.89, 67.00
Dew point: 38.29 degC

Enter Temperature and Humidity as (TT.TT, HH.HH): 
2 Likes

there's a simpler formula see Dew point - Wikipedia

Thanks Golam. Understand most of the formula except
what is the ln in the expression 243.12*{ln ?????
Thanks

Natural Logorithm.

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