Thermometer location

What's the best way to measure temperature in a grow? If you put the thermometer in the light, the light's radiance can give you a much higher reading than even the ambient air temp. If you put the thermometer below the leave canopy, the temperature reading is much lower. Measured at the roots, the temp would be different again. So for the purpose of managing temps within accepted parameters, where is the best place in the grow to measure temperature, at the leaf surface, below the leaf canopy, or at the roots?

I suggest 2 therm locations 1 being at canopy level (hang it from the light or ceiling) and 1 at the exhaust.

the air temperature guidelines for weed are for a thermometer at the top of the plant canopy but shaded from direct light.

Yeah, that^

so how important is the shade on the therm? i mean, i keep mine right at canopy, but i keep it in the light, because if the light is causing radiant heat on the therm, its causing that same radiant heat on the plants is it not?

KlosetKing said:

so how important is the shade on the therm? i mean, i keep mine right at canopy, but i keep it in the light, because if the light is causing radiant heat on the therm, its causing that same radiant heat on the plants is it not?

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it's just the way temps were originally measured in order to separate the effects of radiant heat and air temperature. regardless of radiant heat, if the air temp is above about 85 f the plant's biology slows down. regardless of air temp, if the radiant heat is too high the plant's leaves will burn. so both air temp and radiant heat are important.

desertrat said:

it's just the way temps were originally measured in order to separate the effects of radiant heat and air temperature. regardless of radiant heat, if the air temp is above about 85 f the plant's biology slows down. regardless of air temp, if the radiant heat is too high the plant's leaves will burn. so both air temp and radiant heat are important.

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thanks for the clarification rat! +rep