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Measuring light intensity in PAR

Discussion in 'Estimative Index' started by jonny_ftm, May 18, 2009.

  1. jonny_ftm

    jonny_ftm Guru Class Expert

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    Hi,

    I'm recently questionning myself on the usefullness of such a PAR meter. Recently, I found rather accessible tools, even if still out of my reach in my opinion for the use of it, at only 300 USD, compared to the usual 1000+ USD range

    Quantum Sensor: Apogee Instruments: SPEC SHEETS

    Anyone knows if they are any good for the price?. Also, they sell two different sensors, standard and amplified and I don't figure the difference between them!!

    Any help on other good accessible PAR meters would be great.

    Many thanks for helping
     
  2. Gerryd

    Gerryd Plant Guru Team
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    Hi,

    The Apogee is a good unit and well worth the investment. Tom has seen that the readings are close to the more expensive li-cor meters......

    Not sure about the amplified version, but you want the unit for electrical light calibration and the remote sensor...

    The sensor is on a cable that can then be placed in the tank.

    When I get home at lunch I will post the model # I got.....
     
  3. VaughnH

    VaughnH Lifetime Charter Member
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    "QMSW-SS" is the model number of the Quantum meter we purchased for our Aquatic Plant Club. It works very well and easily. It is the red one.
     
  4. jonny_ftm

    jonny_ftm Guru Class Expert

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    Many thanks for the feedback

    I'm really thinking to spare and get one soon
    I have some other questions though, as the Apogee site is very poorly documented:

    - is it like PH-meter probes: too much care and a short life?
    - do they need frequent/regular calibrations, how is it done and is calibration expensive or easily affordable?
    - finally, I'm used to the Lux/Watt per gallon scales. What should I target as PAR readings for high light setup, non CO2 setup and in-between to have a balanced growth rate

    many thanks for all your help
     
  5. Gerryd

    Gerryd Plant Guru Team
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    Hi,

    I am unsure how they are calibrated or how often, but I have not done mine....it comes calibrated from the factory.

    You don't need to use the meter unless you are measuring the light. It is not like a ph monitor that stays on 24/7.

    I know Tom posted a reply recently on PAR values for c02 and high light, non-c02, etc. A min of 40-50 micromoles would be required to grow most plants.

    High light IME is >150 micro moles. When I had more than that (275-300) growth was ridiculous and I spend all my time trimming.

    I now go from 30-150 in the tank..............c02 is much easier to keep up with at lower light levels.
     
  6. jonny_ftm

    jonny_ftm Guru Class Expert

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    Thanks Gerryd for the answers,

    So, I'm left with this:
    - do they need special care after/between measurements?
    - expectancy of life of the sensor?
    - frequency of calibrations, and is calibration easy/unexpensive?
    - confirmation of your estimations on PAR intensity for high light setup, non CO2 setup and in-between balanced growth for most our plants


    Sad the Apogee site doesn't adress these concernes.
     
  7. Gerryd

    Gerryd Plant Guru Team
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    Jonny,

    Do us all a favor and send them an e-mail with your questions re: calibration and life expectancy...........

    I will if you don't want to................

    But, you ARE the one with the questions :)

    I have found many vendors to be responsive to e-mail........
     
  8. jonny_ftm

    jonny_ftm Guru Class Expert

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    I'll send them an email and let you know,

    Just felt more confortable with a feedback from people here using this tool, based on their user expierience rather than on a vendor claim. For such an investement, I'd trust better some guys like Tom or VaughnH that tested it than a vendor with such a poor product description site
     
  9. jonny_ftm

    jonny_ftm Guru Class Expert

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    Well, looking better in the site I could find this info:

    Recalibration needed every 3 years, RMA needed to use a nominal radiation source for recalibration. It costs about 55 USD international, not sure if shiping is included, but I doubt it. So, it could be better to order a second sensor rather than RMA for recalibration :-(
     
  10. Gerryd

    Gerryd Plant Guru Team
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    Thanks for researching/posting the info.

    It is a nice unit and easy to use...

    I only need it when I am adjusting the lights or deciding when to replace a bulb......usually every 6 months though......
     
  11. jonny_ftm

    jonny_ftm Guru Class Expert

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    I think I'll get one in the next months. Once I do, I'll post again with my PAR measurements to better understand what to do with the values which I expect will be very different if measured at the ground or water surface.

    Thanks again for the feedback on this unit
     
  12. VaughnH

    VaughnH Lifetime Charter Member
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    The sensor is not at all like a pH probe. It is relatively rugged, dry, not wet, no special storage requirements, not delicate. You obviously wouldn't want to drop the sensor, or bang it against things, but just treating it with respect should be adequate.
     
  13. jonny_ftm

    jonny_ftm Guru Class Expert

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    Many thanks for all those info,

    I'm sure I'll get once in the few next weeks rather than months :)
     
  14. jonny_ftm

    jonny_ftm Guru Class Expert

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  15. Tom Barr

    Tom Barr Founder
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    I compared it against our LI 193 spherical integration bulb senson, no different to speak of in our tanks down to 1.2 meters using MH lighting.

    We taped the probes in pairs on the rod we use and took reaings in 5 of the tanks are 20 cm depth increments.

    Maybe 220 vs 223, not much more than that.

    Regards,
    Tom Barr
     
  16. jonny_ftm

    jonny_ftm Guru Class Expert

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    Only good feedback it seems :)

    They changed the model name, it is now MQ-200 with a different look and supposed to be better optimized. You tested the MQ-200 or older model Tom?
     
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