The Importance of Hoods/Covers over Temperature and RH Sensors

[Trash_2002]

One thing people often don't realize, me included, is that this more modern and accurate sensors with housings and etc, if they are installed without a hood under the lights the readings will be pretty far off from the reality, because of radiant heat coming from the lights heating the carcass and throwing off our readings over time.

Without the hoods temperatures in f1 and f2 tents get to 29.5c , 3 degrees celcius off from the reality also RH will be much lower without the hood ( almost 8% lower without the hoods in my case), the effects are instantaneous and pretty severe.


This old school probes sensors, they have a different approach with the probe witch doesn't get too much heated with radiation, the area to heat is much smaller and usually its in the vertical position
but its still off by at least +1c then it should.
Now the reading from the internal unit (not the probe), will have the same effect, plastic will absorb heat and throw off temp and RH readings

Jerry rig some hoods on your sensors, you will get much more accurate readings this way.
Cheers!

 

[Trash_2002]

to maintain a proper LST of 77f/25c this is really useful so we don't get crazy with too high temperature wrong readings from uncovered sensors.

we want our sensors shaded, always.

 

[Zill]

Trash,

Would a wet bulb thermometer help?

Zill.

 

[Trash_2002]

Trash,

Would a wet bulb thermometer help?

Zill.

Didn't tested with one but I think Still same effects apply, the wet bulb water compartment will also get hotter than reality if it's under sun/strong lights. And the dry side will also show higher temps than reality. Temp/RH Measurements with a wet bulb thermometer will still be off, not sure by how much.

 

[Zill]

Yes it will. Perhaps delayed a bit.

What about wrapping the probe with a baggie, sticking that in a vessel filled with ambient water under a shade. Might level out the daily peaks and valleys.

 

[3cats]

Didn't tested with one but I think Still same effects apply, the wet bulb water compartment will also get hotter than reality if it's under sun/strong lights. And the dry side will also show higher temps than reality. Temp/RH Measurements with a wet bulb thermometer will still be off, not sure by how much.

More air movement to eliminate hot spots. I used to suck air right off the light with a 4" flex duct hanging within 2 inches of the lamp. I put screws through the reflector to hold it in place fan on full to remove it from the source.

To help balance your readings.

 

[Trash_2002]

More air movement to eliminate hot spots. I used to suck air right off the light with a 4" flex duct hanging within 2 inches of the lamp. I put screws through the reflector to hold it in place fan on full to remove it from the source.

To help balance your readings.

Yep air movement is crucial for the plants, but the hoods on sensors too, radiant heat on surfaces will be lowered but not eliminated with air movement.

 

[Trash_2002]

Yes it will. Perhaps delayed a bit.

What about wrapping the probe with a baggie, sticking that in a vessel filled with ambient water under a shade. Might level out the daily peaks and valleys.

Yep water will take some time to heat, but it will heat at some point. Shade is crucial for accurate readings.

 

[Trash_2002]

More air movement to eliminate hot spots. I used to suck air right off the light with a 4" flex duct hanging within 2 inches of the lamp. I put screws through the reflector to hold it in place fan on full to remove it from the source.

To help balance your readings.

I mean there's mylar/white panda film and etc reflecting radiant heat too to some extent but sensors shading is necessary.

 

[3cats]

Yep air movement is crucial for the plants, but the hoods on sensors too, radiant heat on surfaces will be lowered but not eliminated with air movement.

I could have my plants within 18" under a 1000w hps without issues. The type of a reflective surface will have an impact too won't it. Like a flat white won't have the same heat relection as say your sheet metal reflector.

 

[Trash_2002]

If you search for top of the line green house sensors, or crazy accurate meteorologic sensors they all have hoods, some even have hoods fixed to the sensors from factory.

 

[Trash_2002]

I could have my plants within 18" under a 1000w hps without issues. The type of a reflective surface will have an impact too won't it. Like a flat white won't have the same heat relection as say your sheet metal reflector.

Yep you could, but the question is, should you?
18" from 1000w hps isn't the best use of light
You can have 1200ppfd+ with DE fixtures much further away than that with much better footprint.

The point I'm making here is for accurate measurements from temp/RH sensors.

 

[3cats]

If you search for top of the line green house sensors, or crazy accurate meteorologic sensors they all have hoods, some even have hoods fixed to the sensors from factory.

Okay I'm in a different world my brain wasn't reading right. You're more into the sensor & their readings than the effect on the plants with your reflector. I saw your dangling hps and went off into another thought all together.

 

[Trash_2002]

Okay I'm in a different world my brain wasn't reading right. You're more into the sensor & their readings than the effect on the plants with your reflector. I saw your dangling hps and went off into another thought all together.

That's a dangling sensor hehehe under LEDs. ;-)

 

[3cats]

Yep you could, but the question is, should you?
18" from 1000w hps isn't the best use of light
You can have 1200ppfd+ with DE fixtures much further away than that with much better footprint.

The point I'm making here is for accurate measurements from temp/RH sensors.

I don't want to knock your sensors but after 20 + yrs of growing under hps one gets a feeling for the effects the light has on the plants. As Humphrey Bogart once said " I don't need no stinking sensors" lol. I gots the feel man. lol

Then I put it away the hps and started using led's, still making a few errors but coming along, after 5 years I grew my fuking plants into the lights this one time one strain all foxtailed another I bleached the top, Vegged too long and they stretched too much but ya I'm still learning.

 

[3cats]

That's a dangling sensor hehehe under LEDs. ;-)

Some say I smoke too much. lol

 

[3cats]

Some say I smoke too much. lol

Sittin here smoking a couple of fatties thinking I'm all smart and shit then ooops there goes another brain cell

 

[Trash_2002]

I don't want to knock your sensors but after 20 + yrs of growing under hps one gets a feeling for the effects the light has on the plants. As Humphrey Bogart once said " I don't need no stinking sensors" lol. I gots the feel man. lol

Then I put it away the hps and started using led's, still making a few errors but coming along, after 5 years I grew my fuking plants into the lights this one time one strain all foxtailed another I bleached the top, Vegged too long and they stretched too much but ya I'm still learning.

Yep same thing here after more than 20 years using hps 3 months ago I switched to LEDs, still learning, and getting half the yield that I was getting from hps.

Thing is the real secret code is to get leaf surface temperature to 77f/25c ( with hps this is so fucking easy), but with LEDs there's some fiddling to do (higher ambient air temps higher RH etc), and having accurate sensors readings helps tremendously in that.
Otherwise photosynthesis craw to a halt when LST is too low, and the dreaded magnesium "deficiency" starts to show its face, the yeild with LEDs will suffer A LOT if not on top of light intensity, LST, air temps and RH.

I'm getting my shit together with LEDs now, changing some approaches as we speak, let's see where this take me in the future.

With hps getting a proper LST with high light intensity (1000ppfd) is so much easier, intuitive I should say.

 

[3cats]

Yep same thing here after more than 20 years using hps 3 months ago I switched to LEDs, still learning, and getting half the yield that I was getting from hps.

Thing is the real secret code is to get leaf surface temperature to 77f/25c ( with hps this is so fucking easy), but with LEDs there's some fiddling to do (higher ambient air temps higher RH etc), and having accurate sensors readings helps tremendously in that.
Otherwise photosynthesis craw to a halt when LST is too low, and the dreaded magnesium "deficiency" starts to show its face, the yeild with LEDs will suffer A LOT if not on top of light intensity, LST, air temps and RH.

I'm getting my shit together with LEDs now, changing some approaches as we speak, let's see where this take me in the future.

With hps getting a proper LST with high light intensity (1000ppfd) is so much easier, intuitive I should say.

I thought I'd learned less is more with led's then I kept 1 flowering girl too far away and miniaturized my buds. They still produced buds but all were real small compared to their mothers. I still have to find the sweet spot with tools and not my eyeballs I guess. I use a lux meter just to get base numbers to go by but I thought my judgment could do it eyeballing without tools. Wrong again another mistake thinking I knew what I was doing.

 

[Trash_2002]

I thought I'd learned less is more with led's then I kept 1 flowering girl too far away and miniaturized my buds. They still produced buds but all were real small compared to their mothers. I still have to find the sweet spot with tools and not my eyeballs I guess. I use a lux meter just to get base numbers to go by but I thought my judgment could do it eyeballing without tools. Wrong again another mistake thinking I knew what I was doing.

There's an app called photone free for Android phones, install it and calibrate it against your light ppfd chart, it's pretty accurate and gets us in the ball park.

Light intensity rules everything else we just can't expect same hps yield giving lower light intensity with LEDs that's a fact.

The most important thing is light intensity, than it's Leaf surface temperature (air temps and RH too so we can get our LST just right), co2, water content/drybacks, rootzone health, wind, nutrients.