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Thema: Kh Director falsche Berechnungen

  1. #1
    Registriert seit
    07.01.2018
    Beiträge
    60

    Standard Kh Director falsche Berechnungen

    Lieber GHL. Kann mir bitte jemand erklären wie werden % bei kh Direktor berechnet?
    Bei 0%- kh6,8. mache 20%-kh7,6? . bei 0%-kh6,7 +7%-kh6,8?

  2. #2
    Registriert seit
    22.08.2018
    Ort
    Amsterdam
    Beiträge
    10

    Standard

    Yes please explain.
    I'm having the same issue:

    Correction set to -4%
    KHD: 8,2 while actual KH was 7,7

    Correction set to -8% to compensate
    KHD: now meassures 7,2 while the actual KH has not changed (still 7,7)

    Now I set the correction back to 0%, to check the base measurement. Based on the first mentioned scenario the KHD should measure 8,5 now.
    However the test result is 7,3.

    At the moment the measurement adjustment is all over the place and I don't understand anymore...

  3. #3
    Registriert seit
    18.02.2009
    Ort
    Kaiserslautern
    Beiträge
    7.631

    Standard

    Hi

    with the "adjustment" setting you can trim the shown value. To trim the value makes sense in these cases:

    a) values from KHD differs to other test methods you are used to and you want still see values in a range you are used to but without chaning the "real" KH level

    b) the values are not 100% correct (you would test this with our reference fluid which has a nominal value of 7.5 +/-0.2) - here you could try to improve accuracy with better calibration of the pumps or take the easy solution and just trim the value without working on the hardware

    what does trimming mean?

    the percentage is added respective subracted

    examples:

    1. real measured KH is 10, adjustment is 20% -> this would give you 10 x 1.2 = 12

    2. real measured KH is 10, adjustment is -10% -> this would give you 10 x 0.9 = 9

    It is hard to determine the correct trim (if neccessary at all) when the input (here the actual measured KH) is fluctuating ( = real aquarium water).
    You need a stable basis for this: Use the reference solution to exclude all other factors.
    Once you see acceptable readings when measuring the reference solution you leave the found factor and re-start your actual measurements.
    No support or warranty issues over PM! Please send PMs to the moderators only if you have general problems with using the forum! Thanks for helping us to keep the support efficient.
    Kein Support oder Reklamationsabwicklung über PM! Bitte senden Sie an die Moderatoren nur PMs bei allgemeinen Problemen mit der Verwendung des Forums! Danke dass Sie uns dabei helfen, den Support effektiv zu gestalten.

  4. #4
    Registriert seit
    22.08.2018
    Ort
    Amsterdam
    Beiträge
    10

    Standard

    OK thanks Matthias.
    Then my understanding and application have been correct.

    My KHD has been functioning rock solid and very reproducible for weeks. Measurement after measurement was 8.1 or 8.2 for days. With the adjustment set to -4%.
    I measure twice daily at 7 am and pm, with a sample volume of 100mL.

    However, based on laboratory measurements and my Hanna checker, I know the KHD measurement is still off by 0.4 to 0.5.

    Therefore I set the adjustment to -8%, after last nights measured KH of 8.2.
    This morning the KHD measured 7.2, where I would expect 7.8 or 7.9. Overnight nothing happened or was done to the tank to explain such a difference.

    In short this has happened:
    4/9 19:16 pm: adjustment -4%, KHD -> 8.2 (without adjustment KH should be 8.54)
    5/9 7:16 am: adjustment -8%, KHD -> 7.2 (without adjustment 7.83)
    5/9 10:56 am: adjustment 0%, KHD -> 7.3 (without adjustment 7.3)

    Wouldn't you agree that this does not depend on using a reference to calibrate or not, but is all down to reproducibility and/or the response to the adjustment value?
    The daily KH consumption of my tank is 1.25 KH per day, so even if my doser malfunctioned without me noticing that cannot explain a KH drop of 1.2 within 15.5 hours. Nor do I think it is possible that my KH consumption has increased by 150% overnight.

  5. #5
    Registriert seit
    07.01.2018
    Beiträge
    60

    Standard

    I think that they do not understand what we are talking about,or they don’t want to understand us !!!
    10:00 0%-6,8kh-water sample in bottle
    10:01 20% adjustment- reading 7,6- same bottle with same water- should be 6,8+20%= 8,16
    Next measurement 10:02 0%-reading 6,8-same water sample-0,1 difference-ok
    10:03- +7% adjust- reading 6,8???? How is it possible ? 6,8+7%=7,2 or 7,3 not 6,8!!!

    I have tried it with water sample in bottle.
    Measurement after measurement,adjustment after adjustment.
    Geändert von AdrianF (04.09.2019 um 18:51 Uhr)

  6. #6
    Registriert seit
    22.08.2018
    Ort
    Amsterdam
    Beiträge
    10

    Standard

    I'm still having these issues. It's driving me nuts.

    Today, with hours or less between measurements.
    KH at 0% 8,9 repeatedly measured
    KH at -5% 8
    KH at -1% 8,6
    KH at -3% 8,7
    KH at 0% 8,9
    KH at -6% 8,8

    So the baseline is always the same and random things happen if I change the correction factor.

    Is it by now at least known by now what causes the correction factor to work so unpredictably?

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