pahval
Well-Known Member
afaik, ir sensors like mlx90614 arent reliable enough to get leaf temperature, they have 1 or 2 °C +/- offset, ive found some research paper using thermistor clamped to a leaf as a viable and more accurate alternative, but i havent done any testing as im waiting for my sensor to come from china...As far as sensors that can do that (ir sensors) that could then send the data and incorporate for vpd calcs and stuff, I've personally only heard of one company or product that does that. It was mentioned in one of solventlessbakenvapes videos. He did a consult with a company dealing with this equipment.
edit:
you can see how it looks here:
LT-1P Leaf Temperature sensor - Phyto-Sensor Group
Subminiature touch probe that measures absolute temperature of a leaf.
www.phyto-sensor.com
about vpd calc:
you only need to calculate setpoint temp or rh, and should be enough for plants, lets say you have 1.2 vpd setpoint and 30°C of ambient air setpoint, you then only need proper RH setpoint to calc from VPD, i used this formula (having vpd setpoint, leaf temp and ambient temp):
double e = 2.7182818284590452353602875;
float rhSet = (((0.61121 * pow(e, ((18.678 - leafTemp / 234.5) * leafTemp) / (leafTemp + 257.14))) - vpdSet) / (0.61121 * pow(e, ((18.678 - airTemp / 234.5 ) * airTemp) / (airTemp + 257.14))) * 100);
edit: i should mention i used buck 1996 formula, i found it to be easy to implement in calculations with mcus like esp32 and even arduino, and precise enough to be accurate, for others you can check here:
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