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Psychrometric calculations on the HP 35s (and 50g)

Posted by Maarten Ambaum (Reading, UK) on 22 Jan 2010, 11:14 a.m.

For those who are interested in meteorology, I wrote a very useable HP 35s program that calculates the relative humidity and vapour density when the temperature and wet bulb temperature are known. I post it here as a nice example of practical use for the HP 35s in science. Other standard methods (computer, tables, charts) are relatively impractical in the field.

It is part of the extra resources that I publish to go with a book on thermal physics of the atmosphere; I will not mention any further details here, lest I get accused of plugging my book. The theory behind wet bulb temperature is somewhat involved and it is therefore impractical to describe it in detail here.

The program description and listing can be found in this 1-page article (pdf).

EDIT: I have now added a RPL code to do the same. It is version 1 and does not have the option to work in Fahrenheit (UserRPL apparently does not allow INFORMs with checkboxes or choose boxes, or customized menus), but it does look nicer than the 35s version.

For both versions, see this webpage.

Kind regards,
Maarten Ambaum

Edited: 12 Feb 2010, 10:00 a.m.

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