How's this for stability? I have a warm exhaust from a 12,000w portable ac unit in my 4x4 tent that blows directly into my 4x8 every 15-20 minutes when it cycles on. Plants don't care about stability, they strive in chaos. They love a warm, dry climate provided they have enough food, h2o & co2
VPD is hocus pocus at best. I haven't found anyplace that can say how it's actually calculated. you don't need to know trig to do simple arithmetic, or be able to see and understand cause and effect. Use that crap to fine tune a proven system maybe, but I don't think it's of much use to confuse noobs with it; I guarantee that a good mentor to teach a proven system to somebody, will get them much better results than any "vpd tools" you give them. I'm not saying they don't have uses. The main use I see for them is tracking and logging data points (which I'm not anal retentive enough to care about). But to believe that that vpd shit is the end all of cannabis growing, is mistaken. How are you measuring leaf temp? A cheap infrared thermometer?... ain't going to cut it, they're not accurate enough. If it's not an accurate measurement then your vpd number isn't true. If the rh/temp probe isn't calibrated properly, same thing. I have multiple hygrometers and thermometers, but none of them agree with one another.... Which ones do I use? Who's vpd chart do I use?, there are different ones of those... Even then you have to have very accurate instruments and very controlled conditions with very little room for error. So now, you've got your $200 inferred thermometer - how and where are the temp and rh measured at? 1 spot? or several then averaged? Same with leaf temp; do you take it at the top of the canopy? Or maybe top middle and bottom and then average?, but how many leaves do you test? 1,3,9,14? How about fans, blowers and ac; on or off? and is it the top of the leafs or undersides? which finger(s)? etc etc... Just so many variables , that personally I doubt it has much use other than setting arbitrary base lines, perhaps a placebo effect on the grower and maybe help with some diagnostics by knowing symptoms of too high/too low vpd, etc...
63/23% is outside, 75/85% is my 4x4 tent, 83/53% is my 4x8 tent, 77/39% is at my bedside
This is from The National Weather Service (Notice it's just vp and not vpd)
Next 3 are from:
https://www.dimluxlighting.com/knowledge/blog/vapor-pressure-deficit-the-ultimate-guide-to-vpd/
This is something I've been saying forever:
lmfao.... "...formulas are beyond the scope of this article." This says all I need to know about vpd. Unless you're in very controlled conditions, I say the numbers you get are like divining rod feedback.... hocus pocus, voodoo shite.
all natural not made up.
