Turning wet and dry bulb temperatures to Humidity and dew point 2

[Farrar]

I need an excel form or formula to calculate Relative Humidity and Dew Point Temperatures by supplying form with Wet and Dry Bulb Thermometer temperatures... Please Help

 

[DRWeig]

Here's a good 'un:

http://www.ringbell.co.uk/info/humid.htm

There's also a free iPhone app, Kele Calculator.

Good on ya,

Goober Dave

 

[IRstuff]

Is your search engine broken?

Is this site's seach engine broken? If so, report problems to toe "Contact Us" link at the bottom of each page.

TTFN

FAQ731-376

 

[walz]

These Formulas are not very simple

I have written a code in VB to run in Excel. Please download the xla file attached(Excel Addin) and follow the following steps

1. Copy it to some folder on your C
2. Open Excel (i assume that you are using Excel 2007, if not it would be somewhat similar steps to do it in 2003). Press Microsoft button and goto Excel Options.
3. Goto Formula Tabs and enable iterative calculation option. Set Max Iterations to 100 and max change to 0.001
4. Now within the same Excel Options, goto Addins tab, click the button Go... in front of Manage
5. Addin Popups, now click browse and goto the location where you have saved this file. Select it and click OK

6. Now You are ready to use the psychrometric formula.
7. Click fx on the formula bar and select the category user-defined.

8. This formula is based on SI Standard Units.
Namely..... Altitude (m), Temp (Deg C), RH (%), W (humidity ratio) in g/kg, Enthalpy in kJ/kg

First field has to be the altitude height (in meters as mentioned above)

Second field has to be Dry Bulb Temp (in DEg C)

Third Field could be any other known parameter amongst WB, W, DP, or Enthalpy (H)

Fourth Field is symbol of third field (This way you tell it that what is the second parameter other than DB). Use it with " mark e.g., "WB"

Fifth Filed is the parameter you want to calculate ... also should be with quotation mark e.g., "DP"

here are all the symbols used for the parameters

a. DB (Dry Bulb Temperature)
b. WB (Wet Bulb Temperature)
c. DP (Dew Point Temperature)
d. H (Entahlpy)
e. W (Humidity Ratio)

No for example given with following

Alt = 10m
DB = 25 C
WB = 16 C

You need to calculate the Dew Point (DP)

here is how you need to write the formula

=psychro(15,25,16,"WB","DP")

Finished ... Enjoy

Note: Instead of direct value input in the formula you can also give the cell referrences of these three inputs

 

[willard3]

So......... you can't find a psychrometric chart? Got all 6that stuff on it and it's a lot easier to use than a computer program.

 

[walz]

Agreed .... its all easy to do any kind of calculations by using a chart.

I did needed it to create spreadsheets with enormous dynamic data, where parameters needed to changed every now and then and going back to chart again n again becomes tediuos. This way i really saved my hours of time.

 

[kapo84]

I have run into this problem various times. One of my colleagues forwarded me this Excel based Psych chart which is written in VBA. You'll have to dig into the code and copy out what you need to make your own formula but it is by no means difficult as long as you have a basic knowledge of VBA.

Enjoy!

** That is a neat add-in tool walz... very useful!

Kapo

 

[kapo84]

Walz,

I don't see the formula "psychro" when I installed your add-in... the only one that resembled your description above was a formula names "fatafut"... it returns a result of -1 regardless of the parameter values.... any ideas?

 

[walz]

Sorry Kapo...

i uploaded my practice file by mistake ..

here is the final one....with the function "psychro"

 

[kapo84]

Works great walz!