Temp issues

smokinthegoodstuff

smokinthegoodstuff

Member
Hi everyone.

I have a clone/seedling box that i made which is 45cmx40cmx55cm and im running a 80w cfl with a shade in there. I have germed two seeds and chucked them in peat pellets to grow. Now with the temp i have noticed that if the digi thermometer is in the light it shows the temp as 31c but if i put it under the seedling tray like in the shade bit then the temp shows at 21.3c. i also have 2 little computer fans going. What temp should i go off? im a little confused.

Thanks
 
qwizoking

qwizoking

Well-Known Member
Put it at canopy..
A little piece of paper will block light.
But your plants will absorb that radiation just like the thermometer did. How hot the plant is, is more what counts than the air around it. Transpiration will cool off innards and airflow + rh will change how high of temps your plant can withstand. 90°F is really the most you should be ok with it running consistently
 
Rhizzologic

Rhizzologic

Member
I agree with quizo, plus most thermometers aren't very precise. I have 4 of them, digital and analogue and they all give different readings.

Acurite is the worst offender:

Readings on this pos vary depending on temps, below 70f and it's too low, above that and it reads too high. Finally said fuck it and bought an IR thermometer, measures the actual temp of your plants instead of the air around them.

http://bestreviewsadvisor.com/top-10-best-infrared-thermometers/ I use the Nubee one, it's the cheapest out of the top 10 and having tested mine against crushed ice and boiling water (2 reference points) I find it to be right on point.
 
Fluff Up

Fluff Up

Well-Known Member
I use a photographers mercury thermometer every so often to "calibrate" (see how wrong it is) to the digital that lives in the tent, if you want to be sure you need to spend money on the measuring device and analogue is going to be cheapest

@Rhizzologic nice idea with the IR but isn't the temperature of the air more relevant? If the air is too hot the plant will transpire more to keep it's own temperature down (which is the reading you're getting), that transpiration is something you want to keep constant and at a reasonable rate,

and another thing were you boiling the water at sea level because if it was above sea level it was below 100 Celsius . . . that feeling that you want to slap me . . . that's totally justified
 
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Rhizzologic

Rhizzologic

Member
Fluff Up said:
I use a photographers mercury thermometer every so often to "calibrate" (see how wrong it is) to the digital that lives in the tent, if you want to be sure you need to spend money on the measuring device and analogue is going to be cheapest

@Rhizzologic nice idea with the IR but isn't the temperature of the air more relevant? If the air is too hot the plant will transpire more to keep it's own temperature down (which is the reading you're getting), that transpiration is something you want to keep constant and at a reasonable rate,

and another thing were you boiling the water at sea level because if it was above sea level it was below 100 Celsius . . . that feeling that you want to slap me . . . that's totally justified
Click to expand...
Relative humidity is a reflection of air temps, and has more of an effect on transpiration and nutrient intake. Temps regulate relative humidity so I would say that air temps are less important than r/h as long as you can control it. That's why growers who use co2 can get away with higher temps, more nutrients, more light, etc. It's like a well balanced symphony. If the temps of my plant are right, and the humidity is within range, then a few degrees difference in air temp is irrelevant, if I'm not mistaken. But a fucked up thermometer that gives inaccurate readings of air temps can be more of a problem than knowing your plant's actual temp, if your humidity is under control.
 
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smokinthegoodstuff

smokinthegoodstuff

Member
Fluff it up does the mercury thermometer work better in the tent?

Growin dad ive got the two little fans going as a exhaust. I did have one as a intake but changed it and that dropped the temp by about 3 degrees lol.

Rhizzo my mate has one of them but for reading the temp for you baby. Might pinch it and try it out lol.
 
Fluff Up

Fluff Up

Well-Known Member
@Rhizzologic thanks for the explanation, basically it's a triangle chart affair, RH, Air Temp, Plant Temp. When you know 2 of 3 are right then 3 has to be in the right place
@smokinthegoodstuff I leave the mercury outside the tent for fear of dropping it on my plants, dunno what it'll do to the plant or me when I smoke it and I don't much care to find out. What makes mine accurate is it increments in 0.5C every 3mm which makes it very accurate (and slow to get a reading). Mercury is a constant, Chinese manufacturing standards are not ;) Basically an analogue thermometer will remain constant
 
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