Thermometer/hygrometer placement

I like to hang my prob in the canopy or just above it. Light will not affect its temp reading to much. Under canopy seems wrong and way above it also seems wrong. going to get different rates for RH and Temp and all that stuff matter where the plants are doing all their work in the canopy. If you canopy is not as levels as in a SCROG net and more like a lot of trees, I would place it where its about middle of the road. tip tops will be different.

I like to keep it intercanopy. This way it's a peak RH% in the room. You can always work in an offset for various concerns. VPD calculations technically need to be based on temprature and RH% at the stomata -- immediately around the leaf -- which will be a few F lower than ambient due to evaporation taking place. Unless using a infrared thermometer on the leaves, an offset will be needed, or just realize your "VPD" will be off from actual. It'll have the same consistency, just a shifted value, so you could learn to react in the same way, regardless. it just won't translate as well to other gardens. you still need to let the plants in your garden guide any fine-tuning. Read the instructions, maybe there is a way to reset the thermometer? if uncertain about accuracy, place it somewhere with a known temperature. if you have 2-way boveda packs could seal it with one of those too as they are +/- 1%. The error of that hygrometer will be +/-5% in all likelihood. The temperatuer will be +/-3-5F. Again, check the manual for specifications. It may need to sit in a new environment for 10-15mins before the readings stabilize, too. No matter where you put it you'll learn how to use it for difference concerns - vpd, avoiding condensation/microbial growth, etc etc

Top canopy for VPD calculation, bottom for testing the circulation fans setup

One of primary drivers of photosynthesis is the temperature held within the leaf, or LST leaf surface temperature, if you measure canopy it will normally fall a few degrees F lower than ambient. I hold 80F which should give me around 77f, optimal at 400ppm, I would give up to 88F under 1500-2000ppm if you aiming for maxing out the curve. Bottom intake, canopy and top of tent should be measured.

Hey bud 😊 I did some test on my grows by placing multiple thermometers at different levels and now I get by by leaving it hanging close to the top canopy of the plant. I was also advised to tape it to the side walls at canopy height but I'd like to keep it at the centre of my tent to get a good overall reading. I still keep multiple devices at different levels as a fail safe but the one hanging above the centre pot is the probe going to my Growhub controller. Hope this is helpful!

I always had couple. Main priority is still canopy top level.