Membership questions? Log in issues? Email info@brewersassociation.org

Author Topic: Refractometer FG Calculator (now with PHP!)  (Read 5509 times)

Offline a10t2

  • Official Poobah of No Life. (I Got Ban Hammered by Drew)
  • *********
  • Posts: 4696
  • Ask me why I don't like Chico!
    • SeanTerrill.com
Refractometer FG Calculator (now with PHP!)
« on: January 07, 2012, 10:07:01 am »
I've had quite a few requests, so I figured I'd post something to let people know it's finally done.

Refractometer Calculator

Any help with error checking and such would be appreciated. Cheers!
Sent from my Microsoft Bob

Beer is like porn. You can buy it, but it's more fun to make your own.
Refractometer Calculator | Batch Sparging Calculator | Two Mile Brewing Co.

narvin

  • Guest
Re: Refractometer FG Calculator (now with PHP!)
« Reply #1 on: January 07, 2012, 11:28:59 am »
Awesome!  Thanks, I've found your spreadsheet to be very accurate so far.

Offline benamcg

  • Cellarman
  • **
  • Posts: 72
Re: Refractometer FG Calculator (now with PHP!)
« Reply #2 on: January 28, 2012, 01:12:57 pm »
Thanks for the spreadsheet- it definetely helps sort out a bunch of confusion I am having with this instrument.  Can someone explain why a refractometer if only good for pre-fermentation readings. I did not see instructions for only using the refractometer pre fermentation, but now I do notice the "SG wort" label under the specific gravities. Does yeast in suspension bend light that much to throw off the FG readings?

Offline denny

  • Administrator
  • Retired with too much time on my hands
  • *****
  • Posts: 27093
  • Noti OR [1991.4, 287.6deg] AR
    • Dennybrew
Re: Refractometer FG Calculator (now with PHP!)
« Reply #3 on: January 28, 2012, 01:14:06 pm »
Thanks for the spreadsheet- it definetely helps sort out a bunch of confusion I am having with this instrument.  Can someone explain why a refractometer if only good for pre-fermentation readings. I did not see instructions for only using the refractometer pre fermentation, but now I do notice the "SG wort" label under the specific gravities. Does yeast in suspension bend light that much to throw off the FG readings?

It's because alcohol has a different SG than water, which throws off a direct reading.
Life begins at 60.....1.060, that is!

www.dennybrew.com

The best, sharpest, funniest, weirdest and most knowledgable minds in home brewing contribute on the AHA forum. - Alewyfe

"The whole problem with the world is that fools and fanatics are always so certain of themselves, and wiser people so full of doubts." - Bertrand Russell

Offline tschmidlin

  • I must live here
  • **********
  • Posts: 8198
  • Redmond, WA
Re: Refractometer FG Calculator (now with PHP!)
« Reply #4 on: January 28, 2012, 01:35:22 pm »
Thanks for the spreadsheet- it definetely helps sort out a bunch of confusion I am having with this instrument.  Can someone explain why a refractometer if only good for pre-fermentation readings. I did not see instructions for only using the refractometer pre fermentation, but now I do notice the "SG wort" label under the specific gravities. Does yeast in suspension bend light that much to throw off the FG readings?
Denny means the the alcohol has a different refractive index than both water and dissolved sugar, which throws off a direct reading.

If plain water is set to zero (by calibrating the refractometer) you could read a mixture of water with either alcohol or sugar.  But in a mixture of all three you can't tell how much refraction is from alcohol and how much is from sugar.  If you have a base reading before fermentation then you can use an equation to determine alcohol content, but in general a hydrometer is easier and more accurate.  Sean's spreadsheet is very good, most of the others are off significantly in practice.
Tom Schmidlin

Offline denny

  • Administrator
  • Retired with too much time on my hands
  • *****
  • Posts: 27093
  • Noti OR [1991.4, 287.6deg] AR
    • Dennybrew
Re: Refractometer FG Calculator (now with PHP!)
« Reply #5 on: January 28, 2012, 03:46:24 pm »
Denny means the the alcohol has a different refractive index than both water and dissolved sugar, which throws off a direct reading.

Yeah, that's what I meant!  First day off the painkillers, but my mind still isn't working right.
Life begins at 60.....1.060, that is!

www.dennybrew.com

The best, sharpest, funniest, weirdest and most knowledgable minds in home brewing contribute on the AHA forum. - Alewyfe

"The whole problem with the world is that fools and fanatics are always so certain of themselves, and wiser people so full of doubts." - Bertrand Russell