Dew point in Fahrenheit

Projects General Guidance
1

Hi!

Im putting together a weather station for calculating Dew point (among other things) and uploading it to Wunderground.

But im having trouble finding a way to calc dew point. I found the below formula.

But since Wunderground needs the value in fahrenheit, and I get my temp in fahrenheit, it feels silly to convert back and fourth.

In short: Is there a similar formula for calculating dew point in Fahrenheit?

H = (log10(RH)-2.0)/0.4343+(17.62t)/(243.12+t);
td = 243.12H/(17.62-H);

RH = Humidity in %

t=temperature in celcius

td= dew point temperature in celsius

Thank you!

2

Convert the temperature from Fahrenheit to Celsius and use the formula you have.

3

you can fill in the celsius to fahrenheit formula at every place of the dewpoint formula and try to simplify it.

tc = ((tf-32)*5.0/9.0);

so the formulas become...

H = (log10(RH)-2.0)/0.4343+(17.62* ((tf-32)*5.0/9.0) )/(243.12 + ((tf-32)5.0/9.0) );
td = 243.12H/(17.62-H);

simplify ==> so the formulas become...

H = (log10(RH)-2.0)/0.4343+(9.79 * (tf-32) )/(243.12 + ((tf-32)0.555555) );
td = 243.12H/(17.62-H);

so in terms of number of math operations it adds 3 operations. That is exactly the amount of converting C->F.

The conversion on the outputside tdC -> tdF takes one additional operation

td = 243.12H/(17.62-H);
==>
tdF = (243.12H/(17.62-H) * 9/5) + 3;
==>
tdF = 437.4*H/17.62-H) + 32;

so only one additional operator.

FOrmulas not tested, but you should get the idea.