Become a TFP Supporter Pool Math Forum Rules Pool School
Results 1 to 5 of 5

Thread: Yokugawa pH/ORP Free Online Handbook - Very Detailed

  1. Back To Top    #1

    Join Date
    Mar 2011
    Location
    Tucson, AZ
    Posts
    11

    Yokugawa pH/ORP Free Online Handbook - Very Detailed

    I found this online, and it contains a wealth of pH and ORP info including temperature corrections, equations, etc.. Most is way beyond me, but I liked the the use of red cabbage or mushrooms to measure pH. Title is 'Back to the pHuture'. Yokugawa mfrs industrial instrumentation.

    The link is: https://www.yokogawa.com/eu/an/analy...H_Handbook.pdf

    The PDF file size is 5.3 Mb.

    Parched
    10K gal, Aqua Blue Pebblesheen, Purex 1/2 HP WhisperFlo pump-3x cartridge filter-gas heater, 2wh Jacuzzi Tracker, TF100, Technopool RX+pH ctrllr, Heliocoil solar panels

  2. Back To Top    #2

    Join Date
    Mar 2007
    Location
    San Rafael, CA USA
    Posts
    12,082

    Re: Yokugawa pH/ORP Free Online Handbook - Very Detailed

    That's an excellent document. While the information on the pH electrode is excellent and indeed pH electrodes follow the Nernst equation such that pH (negative log of hydrogen ion activity) and voltage are linearly related, that is NOT true for real ORP sensors. The RT/nF that they call the Nernst number tells you the mV per doubling of hypochlorous acid concentration in chlorinated pool water. The half-reaction of hypochlorous acid getting reduced to chloride ion is a 2 electron reaction and using n=2 implies 9 mV per doubling. However, actual ORP sensors all have much higher mV per doubling (usually 20 to 28) and they vary depending on the sensor manufacturer. This implies an "n" electron transfer of LESS THAN 1 electron. For example, this post describes ORP going from 700 to 640 mV when the FC goes from 3-4 to below 2. That's at least 60 mV per doubling (or halving) of chlorine concentration and implies an "n" of only 0.15 electrons!

    You've had reasonable results from using your ORP sensor because you regularly calibrate and don't have as many interfering factors. You also replace your sensors annually.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

  3. Back To Top    #3

    Join Date
    Mar 2011
    Location
    Tucson, AZ
    Posts
    11

    Re: Yokugawa pH/ORP Free Online Handbook - Very Detailed

    Interesting- I wonder if, in a real pool, other reactions (chloramines, ...) could also account for such a difference by producing a 'gain' effect as FC varies.

    I noticed that as the pH electrode ages (w/o calibration), it tends to read a higher-than-actual pH, causing the controller to add excess acid. The ORP sensor ages by becoming less responsive (under-reading), so that more chlorine gets added (after reading the handbook, maybe also by seeing a lower pH). This shows up in the test kit readings, and helpfully fails towards a more sanitary pool.

    I was also intrigued by the semiconductor pH sensor, but couldn't find much info on it.

    Parched
    10K gal, Aqua Blue Pebblesheen, Purex 1/2 HP WhisperFlo pump-3x cartridge filter-gas heater, 2wh Jacuzzi Tracker, TF100, Technopool RX+pH ctrllr, Heliocoil solar panels

  4. Back To Top    #4

    Join Date
    Mar 2007
    Location
    San Rafael, CA USA
    Posts
    12,082

    Re: Yokugawa pH/ORP Free Online Handbook - Very Detailed

    It happens in standard chlorinated water, not just in a pool. If you look even at George Clifford White's "Handbook of Chlorination and Alternative Disinfectants", you will find all kinds of inconsistencies even in pure water with only chlorine added. There is no ammonia or organics added so there are no chloramines. See this post for some of the craziness associated with ORP. The Figures in White's book varied in mV/doubling from 10 in distilled water to 12-20 in pools to 35, 30-40, 15-20 in three different figures of non-pool chlorinated water. The absolute ORP level (i.e. the offset) varied as well as the slope.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

  5. Back To Top    #5

    Join Date
    Dec 2013
    Location
    SF, CA, USA
    Posts
    40

    Re: Yokugawa pH/ORP Free Online Handbook - Very Detailed

    aargh, the detail! thank god there are a few blank pages for notes.
    plumbing up wall-mounted equipment and plenty gauges below a 500G wooden outdoor hot tub.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •