ispindel/ubidots SG Temperature correction

Discussion in 'Homebrewing' started by Beejay, Dec 15, 2020.

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  1. Beejay

    Beejay Pooh-Bah (2,559) Dec 29, 2008 Virginia
    Pooh-Bah

    I recently built an ispindel, and got it working in a lager. My fermentation schedule has a rise in temp before crashing, and the ispindel was basically jumping all over the place on the gravity reading. I've been doing a lot of research into how to correct for temperature, even found a formula for it, but I can't seem to phrase the formula in a way the Ubidots will calculate as a derived variable...

    Anyone have the same issue, or any solutions? Or anyone just good enough at speaking computer math to tell me how to adjust the formula so it works?

    Here is the formula I have found:


    CG = corrected gravity
    MG = measured gravity
    TR = temperature at time of reading
    TC = calibration temperature of hydrometer



    CG = MG * ((1.00130346 – 0.000134722124 * TR + 0.00000204052596 * TR – 0.00000000232820948 * TR) / (1.00130346 – 0.000134722124 * TC + 0.00000204052596 * TC – 0.00000000232820948 * TC))

    Source: https://straighttothepint.com/hydrometer-temperature-correction/
     
  2. riptorn

    riptorn Pooh-Bah (1,776) Apr 26, 2018 Georgia
    BA4LYFE Society Pooh-Bah Trader

    This works for me in Excel.
    1. Create a new spreadsheet.
    2. Cell A1 will hold your measured Specific Gravity reading.
    3. Cell A2 will hold the measured temperature of the wort.
    4. Cell A3 will hold your hydrometer's calibration temperature (either printed on the hydrometer scale or in the hydrometer instructions).
    5. Copy and paste the formula shown below into cell A4.
    =ROUND(A1*((1.00130346-0.000134722124*A2+0.00000204052596*A2^2-0.00000000232820948*A2^3)/(1.00130346-0.000134722124*A3+0.00000204052596*A3^2-0.00000000232820948*A3^3)),4)

    Hope I didn't bugger up the copy/paste.
     
  3. Beejay

    Beejay Pooh-Bah (2,559) Dec 29, 2008 Virginia
    Pooh-Bah

    This totally works in Excel, but Ubidots for some reason won't let me sub out the cells for variables.... grrrr...

    Thank you!
     
  4. Beejay

    Beejay Pooh-Bah (2,559) Dec 29, 2008 Virginia
    Pooh-Bah

    Ok, I think I got it.... turns out Ubidots really doesn't like spaces, and all the copied minus signs were jacking it up.. Will need to do further testing...
     
    riptorn likes this.
  5. Beejay

    Beejay Pooh-Bah (2,559) Dec 29, 2008 Virginia
    Pooh-Bah

    Thanks to the Excel formula I can double check my work pretty easily. For some reason even though I am reading in ºF the formula is working better with ºC for the calibration temp.
     
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