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Thread: Do I need to Calibrate?

  1. #1
    Regular Vistor cmacld's Avatar
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    Do I need to Calibrate?

    A few days ago I installed the PMK on my system. Having a par meter is new to me. At what point should i be reading measurement?

    Right now i get no reading until my blue LEDs have ramped up to 20%.
    Shouldn't there be at least some reading with any low light level.
    I do understand that the reading is skewed by the short wavelength of light, but when i had the meter out in a lighted room i also go no readings there, it wasn't until i physically put a direct light source above it that it read.

    Seem right?

    The real question is should I calibrate it to read lower light levels?

    Thanks for any time and input!!

    Cheers,
    Chad
    Cheers,

  2. #2
    Regular Vistor cmacld's Avatar
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    No one has any experience here?


    Cmac

  3. #3
    Master Control Freak RussM's Avatar
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    PMKs w/ PAR sensors are tested & calibrated before shipment. Without a known reference lighting source, you really can't calibrate it. The only thing a user can do is adjust the zero point a small amount if it shows a low reading in total darkness.

    What you see is similar to my own experience. Being designed to measure PAR vs being a general luminosity sensor, the PAR sensor is particular about the spectrum. In my brightly-lit office (standard T8 fluorescent tubes), my PMK only reads around 10 with the PAR sensor in air points up towards the light. If I hit the sensor with a moderately strong regular white LED flashlight at about 6", it only reads about 120. Hit it with an Orphek AzureLight (blue LEDs) from the same distance, and it reads over 500.
    Please do not send me PMs with technical questions or requesting assistance - use the forums for Apex help. PM me ONLY if the matter is of a private or personal nature. Thanks.

  4. #4
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    Is there anyway we can confirm what we "should" have as far as PAR, i have two AI Vega's and getting some low #'s, although my lights are on pretty bright.

    It drops down to zero even when there is light (i know not all light spectrum is equal) But over the past 4 days it has averaged at 42.71 and had a Max of 172.... (the PMK is at the bottom of my tank (92gl corner) right under one of the lights).

    My Vegas are brightest from 12pm to 8pm getting 75% on the blues, 45 on the green an red, and 56% on the white....so how can i tell if this is an actual accurate #...

  5. #5
    Regular Vistor
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    Quote Originally Posted by DrPaul84 View Post
    Is there anyway we can confirm what we "should" have as far as PAR, i have two AI Vega's and getting some low #'s, although my lights are on pretty bright.

    It drops down to zero even when there is light (i know not all light spectrum is equal) But over the past 4 days it has averaged at 42.71 and had a Max of 172.... (the PMK is at the bottom of my tank (92gl corner) right under one of the lights).

    My Vegas are brightest from 12pm to 8pm getting 75% on the blues, 45 on the green an red, and 56% on the white....so how can i tell if this is an actual accurate #...
    does the sensor need to be pointed directly up? or can it be slightly askew?

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