(42S) Menu controlled Dew Point (°C) and Relative Humidity calculations

[Bernd]

Hello,

since I have already benefit so much from the shared knowledge of you guys here, I felt the urge to give back a little of it. So now as this is my first post in this forum I would like to contribute another dew-point program to the community.


About the program

With this program, you can calculate the dew point from air with a given (measured) temperature and relative humidity. Once the dew point for that air has been calculated, you can calculate how the relative humidity would change when the temperature changes.

Please check the attached documentation for detailed information about the program.

And also feel free to comment - I'm sure my programming style is not perfect yet, and a lot of room for optimization - as there's a lot more to learn about programming the smart way.


How it all started

On a hot summer day some years ago, I had opened the windows to my basement to let the hot air from outside heating up my basement. Some hours later, I found that the floor-tiles in the basement were wetted by the dew (which had been contrary to my believe that I can fight the humidity in the basement by letting hot air from outside to come in). At that time, I didn't know anything about dew points, and of course, I didn't know what an h-x-diagram was.

Some years later, I was again confronted with dew point and humidity calculations while being into the design of a data-center. This is when I learned how to read and use h-x-diagrams.

About a year ago, I got to own an old Olivetti desktop calculator which was my first contact to an RPN-like machine. I liked this ingenious way of calculating, and so the next logical consequence led me to discover Thomas Okken's incredible Free42. After having started using Free42 only for normal calculations, soon the desire of being able to program this machine arose. Finally, I really love the way of thinking and calculating in RPN - a big thanks to Thomas for making this possible.

Now with the knowing about the power of HP-42S programming, I found this dew point calculations worth for being my first project.