Hello,
I am taking readings in the greenhouse with a temperature and Humidity Meter that is measuring in Celsius and Relative Humidity. However, in an attempt to better understand the effect of humidity on the plant I would like to add a column to the chart that illustrates the VPD (vapor pressure deficit).
I have looked around for sources on this subject and found a thread on this site which brought me to the forum...
http://www.excelforum.com/excel-gene...x-formula.html
The formula is not giving me the results that I would expect as most greenhouse VPD readings to be between 2 and 8. see chart below.
2014 03 25 Humidity VPD.PNG
[code]A -10440.397
B -11.29465
CC -0.027022355
D 0.00001289036
E -0.0000000024780681
F 6.5459673
TC SEE TABLE
TR [°R]*=*([°C]*+*273.15)*×*9⁄5
VPsat 10 VPsat B10: =EXP(A/TR+B+CC*TR+D*TR^2+E*TR^3+F*LN(TR))
[code\]
when I use the following numbers I get VPD of 0.32093
Temperature Humidity Rankine VPD
19.109 °C 17.4 %RH 526.06 0.32093053
this looks incomplete as I am looking for VPD and this formula says VPsat. Do I need another step here?
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