thermometer question

Discussion in 'Growing Marijuana Indoors' started by qz420, May 14, 2006.

  1. I heard that to get an accurate reading of the temp. the thermometer shouldn't be in any kind of direct light. Is this true?

    I have 2 thermometers in my grow box right now and they both read a different temp. one I have is at the top of the grow box where the tallest part of my plant is, and the 2nd one is ontop of my bubble bucket. the low one reads 79 and the top one reads 85. I think the one at the top of the grow box reads higher temps cuz its in direct light while the bottom one is shaded by leaves. So which of these is a more accurate temp???
  2. 79 + 85 / 2

    average them... just a guess.
  3. That temp difference may not be artificial from direct light on one thermo -- the top of the box should be expected to be warmer. Heat rises and also is generated by the light at the top. You actually have a gradient of temperatures throughout your box.

    Your concern should be the higher temp of the two on the high end and the lower temp of the two on the low end, those represent the extremes of your box's conditions. You could try shading the upper thermo in its present location to see if that makes a difference, otherwise I would take it at face value.

    85 is more than the ideal 74-78 or so range but still should not be too stressful for the plants.
  4. hey toasty, u just posted your 420th post!! You should celebrate :)
  5. This whole 'accurate' stuff you hear about is in comparison to the weather forecasts.
    There they display the temps based on thermometers in the shadow.
    If you want to test 'accuracy' of a thermometer, compare with another termometer, so switch the one at the top of your box with the one at the bottom.

    In your case both temps are probably 'correct'. After all, your plant is directly shone upon. I'm certain you are familiar with the concept of sunshades inside a house...:D

    This is because there are two types of heat : radiation heat and direct contact heat. For the first we use sunshades to counter it, for the second we have insulation material with air/gas bubbles/pockets inside it.

    Big temperature differences inside your box, whilst allmost unavoidable, means your internal air circulation is not optimal.
  6. Oh, the irony...if I acknowledge your comment my counter goes to 421...and just did.

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