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 Leaf temp and tent temp

Discussion in 'Pulse Labs' started by Simplicio, Mar 10, 2018.

  1. Simplicio

    Simplicio Smoke Cannabis Live with Friends on AFN

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    Transpiration cools leaf surfaces, so the actual leaf temp is typically less than tent air temp. I've been curious about how much less. There are 5 cheap RH/temp meters placed around the tent near the canopy surface, along with Nano. An infrared gun thermometer was used to measure leaf temperatures. The 5 RH/Temp readings were averaged to get single values, and 4 IR thermometer readings were also averaged. For a total of 33 trials (9 measurements each trial), spread over 5 days, the leaf temp appears to be 7 F lower than the ambient air temp. I saw that many people were assuming 5 F in a few internet posts. This has important implications for VPD calculation. The tent has averaged about 80 F air temp and 60% RH, yielding a VPD of around 1.4 kPa, which is outside the approximate recommended range of 0.4 to 1.2. If the 7 F cooler leaf temp is used instead, then the VPD is 1.1, within the recommended range.

    Being able to set Nano's temp/RH values to match tent values would be very useful.
     
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  2. lunarman

    lunarman Smoke Cannabis Live with Friends on AFN

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    Your post isn't in the Pulse Labs board @Simplicio

    Its in the level up, Grow Room Components. So people from Pulse Labs might not realized you posted this.
     
  3. Simplicio

    Simplicio Smoke Cannabis Live with Friends on AFN

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    Thx for the warning.
    I'll try to cut and paste a new post.
     
  4. Duggy

    Duggy Berries of Blue Staff Member Global Moderator (SA)

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    I'll move your post to Pulse section mate...
     
  5. getpulse.co

    getpulse.co cannanerd AFN Authorized Vendor

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    Thanks @Duggy

    @Simplicio
    Very interesting data you've collected there. Given the meters were placed around canopy level, that is a larger differential than I would have thought.

    Just to clarify, are you suggesting a user-inputted offset in order to make the data reflect the leaf temp?
     
    Last edited: Mar 13, 2018
    Duggy likes this.
  6. okPeet

    okPeet Welcome to the CannaZone AFN Authorized Vendor

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    @Simplicio what kind of lights were you using?
     
  7. Simplicio

    Simplicio Smoke Cannabis Live with Friends on AFN

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    Using a Platinum p-600 in a 3 x 3 tent with lots of air circulation.
    I'd like to be able to adjust the temp and humidity readings by any amount.
    With this capability, Nano could be placed anywhere in the tent, and then have its temp/RH values adjusted to canopy values.
    For example, if tent air temp is 80 F, and leaf temp is 73 F, I'd like to be able to force Nano to read 73 F.
    Also RH readings are sometimes suspect, and it would be nice to be able to calibrate that.
     
  8. okPeet

    okPeet Welcome to the CannaZone AFN Authorized Vendor

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    RH calibration is coming today. I can add a temperature calibration function as well.

    I'd worry about calibrating to a strict offset because leaf temperature changes based on humidity, light levels, where you're measuring the leaf temp, etc. There are a lot of factors that go into it. However, if it is something that's desired, i have no issues providing it!
     
  9. okPeet

    okPeet Welcome to the CannaZone AFN Authorized Vendor

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    Humidity calibration added, check out the release thread.

    https://www.autoflower.net/forums/threads/new-release-2018-03-14-humidity-calibration.64671/
     
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