Where to measure temps in a grow room - Radiant or ambient?

[SolMJ]

Hello 420,

I'm wondering where you should place a thermometer in a grow room for an accurate reading of the temps. It seems that placing them under the light is not ideal because then its only measuring radiant light when in fact its ambient temperature that counts. This kinda makes sense since temps are always measured in the shade. I placed mine on top/side of the reflector & the difference from under the lights is substantial. If this is the right way to do it then all that matters in the canopy is that the lights are not too hot/too close using the hand method. In any case it sounds that plants can handle higher radiant temps better than ambient. Any thoughts??

Thanks

 

[Ricky Bobby]

I have sort of wandered this myself. I keep mine in the upper and outter corner of my room. I figure it's out if the light and the most heat and moisture are going to farther up high and away from the fans and that will give me an idea of the overall picture of what's getting circulated around the room. If it's under the lights, above the reflector or in front of the fan I think you will have false readings

 

[ODtheGreat]

I try for the same level of the top or middle of my plants. Use more than one thermometer even.

 

[Dave Groomer]

Ideally I would say at the top of your canopy. For convenience, mine sits on top of my light. My temps are pretty stable at 84 there. Probably a degree or 2 cooler at the top of the plants.

 

[SolMJ]

So none of you actually place it under the lights. I put mine on top of the reflector earlier & according to the readings (25.8c or 78f) I can easily lower the lights for an extra 10,000lux (lets party!!)...but im worried in case it ends up burning the plants? most people I see place their thermometer under the lights so whats going??

 

[ODtheGreat]

I do have them under the lights. I assume the plants are basking in the light so the thermometer should be to get an accurate idea of how hot your plant is getting. I see how hot it is at the very top nugs and then one that's about where the middle of the plants are. The thermometer in the middle is more shaded. I could be wrong but that's what I've been doing. I've fried a couple plants before getting them too close to the light, that was no fun. So temp is one of my main focuses.

 

[Dave Groomer]

So none of you actually place it under the lights. I put mine on top of the reflector earlier & according to the readings (25.8c or 78f) I can easily lower the lights for an extra 10,000lux (lets party!!)...but im worried in case it ends up burning the plants? most people I see place their thermometer under the lights so whats going??

My LEDs don't get hot enough to burn the plants. Put your hand directly under it. Not to hot. What you need to worry about is getting the full spectrum of lights. Too close and the LEDs wont blend. I would go closer then 12-14"

 

[JoseQuervo]

LOL. You can buy a pile of the indoor / out door thermometers on egay for a few bucks. I got 10 of them for like 15 bucks. I like to keep on sitting on top of each light. And then I have the probe part so it is around the height of the canopy. I also have one hanging in the center or the room about equal from the floor and ceiling, and then I have one sitting on the ground under the plants. I kinda just average it all out, our going by the one hanging in the center of the room for a quick check. I also picked up one of those laser thermometers for about $12 from the same place. Then you just take a bunch of readings in a few seconds.

 

[ConstantGreen]

My favorite way to measure temp is with an infrared thermo gun.

Just pull the trigger and point at the canopy, instant temp reading of the leaves. Scan it around the room to pick up on hotspots. It's so useful for so many different applications. Definitely worth $40 IMO.

But if you're just using a traditional thermometer, I would think closest to the buds/canopy for an accurate reading.

 

[Dave Groomer]

My favorite way to measure temp is with an infrared thermo gun.

Just pull the trigger and point at the canopy, instant temp reading of the leaves. Scan it around the room to pick up on hotspots. It's so useful for so many different applications. Definitely worth $40 IMO.

I have one I use when making oil. Never took it out of the kitchen to check the tents.

 

[ConstantGreen]

I have one I use when making oil. Never took it out of the kitchen to check the tents.

Lol yea I only use it once in a while to check the tent, but all the time when cooking. So awesome just peeking open the oven and reading how cooked stuff is.