Tent temp vs leaf temp help please
- Thread starter bd6187
- Start date
FirstCavApache64
Well-Known Member
What are you measuring with that says 82 degrees and where in the tent is it positioned? You should be taking your temp readings at the top of the canopy and a cheap IR temp gun will give you leaf surface temps for VPD calculations.
bd6187
Well-Known Member
I used a regular thermometer and set it under the light the same height as the top of the plants
MissinThe90’sStrains
Well-Known Member
Air circulation will help stabilize your overall temps. Remember, hot air rises and cooler air settles. Temperature is a measure of the average, and it can vary within your tent.
FirstCavApache64
Well-Known Member
I used to use a cheap humidity and temp sensor from Amazon for years. It was set at the top of the canopy and held to the tent pole with a magnet. I got a Bluetooth combo pack recently that has 3 sensors for temp and humidity and the base station. I have the sensor set at canopy level and it's pretty accurate. I'd try to check the accuracy of both the thermometers you're using as 10 degrees is a big difference between the two.
PopAndSonGrows
Well-Known Member
Get one of these to check leaf surface temps. Best way to know what the actual temp is on your plant vs the air temp around them.
coreywebster
Well-Known Member
No you dont want to read under direct light.
Your wanting to measure air temps.
Google Stevenson screen.. that's how the meteorological society measure air temp while preventing interference from light
Thermometer should be above light line or shaded from direct light
coreywebster
Well-Known Member
There's a difference between air temp, radiant heat and LST
medidedicated
Well-Known Member
I thought my temps were mismatched from crammed space, good to know!
Will move my caliber. I see so many, put it right where canopy is.
Jjgrow420
Well-Known Member
Microclimates are real in cramped spaces where it will be warmer or hot above and cold below, if you don't have good air circulation. It can cause dew which can lead to other problems like bud rot, mold, mildew etc.
medidedicated
Well-Known Member
It is 88F on the thermo and 74F leaf teamp, like no matter where I place it.
The light range covers the whole canopy so I put it above the light and waiting for results.
I got micro climates yea. I need 2.5x2.5 to grow comfortably, 3x3 for photoperiod.
Billy the Mountain
Well-Known Member
Under LED lights, leaf surface temps should be ~2-3 degrees cooler than the ambient air due to transpiration.
One of your readings is likely erroneous.
medidedicated
Well-Known Member
I read, if recalled correctly that with leds, vpd ranges in cooler temps can cause a 10F difference and that it improved with upping temps which worked in my case.
Caliber is over a year old but did not think the thermo needed calibration or could be but like one said, having it grilled under the light and being black may absorb heat.
I know 5F offset between objects and plants is normal but this is 10F + but crammed too, micro climates. I use laser gun pew pew haha I am stoned.
Billy the Mountain
Well-Known Member
"vpd ranges in cooler temps can cause a 10F difference"
- ???
One suggestion would be to use the same meter (IR gun) and measure a painted surface (similar IR emissivity) and a transpiring leaf. The difference will be far less than 10°.
medidedicated
Well-Known Member
I could not find the post again, it was a commercial size grow and brand that had that and resolved the leaf temp reading issue by turning up humidity and air temps.
Turning up temps shortened the gap but it is still there. Will try that out. Or use a better device/probe.
medidedicated
Well-Known Member
My caliber is reading much closer to leaf temps now. Learing something every day lol. 80F and leaf temps are 71 - 73 - 76F, 5 degree offset like they say should be.
Caliber placed above the light beams.
This is about as tedious as monitoring ph lol.
Caliber placed above the light beams.
This is about as tedious as monitoring ph lol.
Yeah, I'm stoned. What is a caliber?
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medidedicated
Well-Known Member
Hygro meter. If you were joking, I suck at sarcasm, if you weren’t, I see people just call them that, hydro slang lol.Yeah, I'm stoned. What is a caliber?
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ALPHA.GanjaGuy
Well-Known Member
I don't follow? You had to put your thermometer/hygrometer above the lights?
If that is what you mean then you are just seeing the temps at the top of the tent not at the top of your canopy so that temp may not be the temp the plants are seeing depending how much temps vary in your tent
medidedicated
Well-Known Member
Yea, I put it above the light but it is a small space so it is hard to avoid. I consider that a better reading and kept it there since.
Edit it is actually just under the light but above the beam of light.
One said it can interfere with readings having it under the light. I did not read the link, I just put two and two together.
It reads like 10F hotter under the light. That makes leaf temps 75 and room temp 90 or 92F. That makes vpd analysis harder.
I think one is saying vpd is about measuring room temp/rh and leaf surface. Rh reads more steady too now.
You aren’t putting in what the micro climates are or the temp of the hygrometer itself.
Even if not, it is always going to be hotter right under the lights but the vpd has no slot for “temps between colas or layers of canopy.”
Correct me if I am wrong, I just thought I learned something critical here.
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