VPD is a great thing to learn for optimizing your environment. Chart examples: Check out @SuperiorBuds integration of VPD calculations into his set-up, over here:
I’ve been using the VPD class (ported to C#) for quite some time now. I recently went ahead and made a new page that can render the VPD chart around a specific point (Temp/RH). This will be used to render an overlay on my stream showing the real-time VPD using SensorPush data.
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Thanks again for this @Northern_Loki – this was a big help getting started.
@plant also did something in Javascript:
Loki’s is much more sophisticated and useful; but for anyone who is scared with compiled programs and likes the web I transposed his to plain jane JavaScript. Prints out the tables and nothing more. I used the buck 1981.
Feel free to modify and play with it anyway you like =)
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Formulas for doing the calculation yourself are there as well:
There are several VPD algorithms that are essentially estimations applicable to specific circumstances. Here are a couple that are most applicable (with reasonable error) for the temperature ranges we’d typically consider. It’s been awhile since I looked at this but from what I recall, three steps, here:
Saturation pressure (aka partial pressure of water)
Vapor pressure
Vapor pressure deficit
(1) Saturation pressure
These calculate the “saturation pressure”:
Goff Gratch (1984):
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whe…
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