Author Topic: Improved Refractometer Correction calculator  (Read 5751 times)

Offline Big Monk

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Re: Improved Refractometer Correction calculator
« Reply #165 on: February 21, 2018, 04:13:06 AM »
This is crazy.  We're all getting different answers.  Novotny and Old Cubic are most accurate for mine all the way across.

I modified my sheet to calculate attenuation and alcohol for each correlation and entered in stats from 12 sessions. Novotny Linear and Cubic and Old Cubic WAY undershot every batch and returned unrealistic attenuation and ABV Numbers.
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Offline dmtaylor

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Re: Improved Refractometer Correction calculator
« Reply #166 on: February 21, 2018, 04:18:19 AM »
This is crazy.  We're all getting different answers.  Novotny and Old Cubic are most accurate for mine all the way across.

I modified my sheet to calculate attenuation and alcohol for each correlation and entered in stats from 12 sessions. Novotny Linear and Cubic and Old Cubic WAY undershot every batch and returned unrealistic attenuation and ABV Numbers.

And I get the opposite, from 5 data points though, not 12.  Maybe I'll change my tune after 12.
Dave

The world will become a much more pleasant place to live when each and every one of us realizes that we are all idiots.

Offline Robert

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Re: Improved Refractometer Correction calculator
« Reply #167 on: February 21, 2018, 04:24:51 AM »
This is crazy.  We're all getting different answers.  Novotny and Old Cubic are most accurate for mine all the way across.
I'm almost ready to propose a surprisingly commonsense solution.  We need no correction beyond our well-known factor for our own instrument for wort.  Simplify brew day by using refracto.  Ignore mid fermentation.  Use a hydro for FG, but wait until time tells you you're probably there.  You can surely afford one hydro size sample even on a small batch.  I have a vague recollection this is how we homebrewers first got interested in refractometers.
Rob
Akron, Ohio

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Offline DeeGood888

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Re: Improved Refractometer Correction calculator
« Reply #168 on: February 21, 2018, 10:17:29 AM »
Need to bookmark this  ;D

Offline Big Monk

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Re: Improved Refractometer Correction calculator
« Reply #169 on: February 21, 2018, 12:52:30 PM »
This is crazy.  We're all getting different answers.  Novotny and Old Cubic are most accurate for mine all the way across.

I modified my sheet to calculate attenuation and alcohol for each correlation and entered in stats from 12 sessions. Novotny Linear and Cubic and Old Cubic WAY undershot every batch and returned unrealistic attenuation and ABV Numbers.

And I get the opposite, from 5 data points though, not 12.  Maybe I'll change my tune after 12.

Just to satisfy my own curiosoty Dave: Why the fudge factors in your old cubic and Novotny linear calculations? Is it just that those modified values are just closer than the New cubic and New Linear calcs so you call that good?
“We are what we repeatedly do. Excellence, therefore, is not an act, but a habit.”   Aristotle

“To my big brother George. The richest man in town.” Harry Bailey

“Stand and be true.” Roland Deschain

Check us out at www.lowoxygenbrewing.com

Offline dmtaylor

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Re: Improved Refractometer Correction calculator
« Reply #170 on: February 21, 2018, 01:13:02 PM »
Just to satisfy my own curiosoty Dave: Why the fudge factors in your old cubic and Novotny linear calculations? Is it just that those modified values are just closer than the New cubic and New Linear calcs so you call that good?

Yes.  Trying to fit the line better, assuming the curvature is correct but vertical placement is not.  Call my versions "the Taylor formulae" if you prefer.  Originally, I had applied fudge factors to Terrill's formulae based on Terrill's own analysis... but found those fudgers unnecessary to fit my own data set.  The reasons for doing so were sound enough for me to go ahead and use fudgers for other formulae where necessary.  See writeup from Terrill here, where he suggests his own New Cubic averages high by about 0.0007, but the Old Cubic was low by about 0.0017... so I added those fudge factors into my own spreadsheet originally right off the bat, then tweaked from there based on the line in my spreadsheet marked "New ABS Method" with a goal of zero of course, which unlike Terrill's "Mean discrepancy" which blends negative and positive values, my method uses absolute value distances from the goal line, yadda yadda.  Anyway...... here's Terrill's own analysis of the accuracy of his own formulae:

http://seanterrill.com/2011/04/07/refractometer-fg-results/

I guess you could say, I am attempting to normalize the playing field, instead of allowing each formula to average too high or too low.  Let's assume the curvature is correct but for some reason the people taking measurements aren't calibrating their hydrometer accurately, or whatever, which would result in a consistently high or low correlation.

There you have it.  I'm finally done editing this post (edited it about 6 times in the past 8 minutes).
« Last Edit: February 21, 2018, 01:21:17 PM by dmtaylor »
Dave

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Offline Robert

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Re: Improved Refractometer Correction calculator
« Reply #171 on: February 21, 2018, 01:28:57 PM »
^^^^^
Wherein Terrill says:

"In situations where the FG needs to be known precisely, testing with a properly calibrated precision hydrometer remains the best option."
Rob
Akron, Ohio

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Offline Big Monk

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Re: Improved Refractometer Correction calculator
« Reply #172 on: February 21, 2018, 01:30:07 PM »
Just to satisfy my own curiosoty Dave: Why the fudge factors in your old cubic and Novotny linear calculations? Is it just that those modified values are just closer than the New cubic and New Linear calcs so you call that good?

Yes.  Trying to fit the line better, assuming the curvature is correct but vertical placement is not.  Call my versions "the Taylor formulae" if you prefer.  Originally, I had applied fudge factors to Terrill's formulae based on Terrill's own analysis... but found those fudgers unnecessary to fit my own data set.  The reasons for doing so were sound enough for me to go ahead and use fudgers for other formulae where necessary.  See writeup from Terrill here, where he suggests his own New Cubic averages high by about 0.0007, but the Old Cubic was low by about 0.0017... so I added those fudge factors into my own spreadsheet originally right off the bat, then tweaked from there based on the line in my spreadsheet marked "New ABS Method" with a goal of zero of course, which unlike Terrill's "Mean discrepancy" which blends negative and positive values, my method uses absolute value distances from the goal line, yadda yadda.  Anyway...... here's Terrill's own analysis of the accuracy of his own formulae:

http://seanterrill.com/2011/04/07/refractometer-fg-results/

I guess you could say, I am attempting to normalize the playing field, instead of allowing each formula to average too high or too low.  Let's assume the curvature is correct but for some reason the people taking measurements aren't calibrating their hydrometer accurately, or whatever, which would result in a consistently high or low correlation.

There you have it.  I'm finally done editing this post (edited it about 6 times in the past 8 minutes).

Understood. I'm backfitting old data so it will be nice to log the next 8-10 sessions with fresh eyes and see where I land.
“We are what we repeatedly do. Excellence, therefore, is not an act, but a habit.”   Aristotle

“To my big brother George. The richest man in town.” Harry Bailey

“Stand and be true.” Roland Deschain

Check us out at www.lowoxygenbrewing.com

Offline Robert

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Re: Improved Refractometer Correction calculator
« Reply #173 on: February 23, 2018, 02:10:46 AM »
I have a new set of precision Plato saccharometers arriving tomorrow.   Over time I will try to provide you guys some more data.  Will confirm my correction factor and post any measurements on this thread.

EDIT Perhaps it would be more helpful if I just posted raw data for batches where available:  OG,  mid, and FG  WRI  and saccharometer readings.  Let me know if it would be of any use.
« Last Edit: February 23, 2018, 02:31:24 AM by Robert »
Rob
Akron, Ohio

"There is always a well-known solution to every human problem -- neat, plausible, and wrong."  -- Mencken

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Offline Pricelessbrewing

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Re: Improved Refractometer Correction calculator
« Reply #174 on: February 26, 2018, 02:20:19 AM »
I have a new set of precision Plato saccharometers arriving tomorrow.   Over time I will try to provide you guys some more data.  Will confirm my correction factor and post any measurements on this thread.

EDIT Perhaps it would be more helpful if I just posted raw data for batches where available:  OG,  mid, and FG  WRI  and saccharometer readings.  Let me know if it would be of any use.

Give me all of the data!

Offline Robert

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Re: Improved Refractometer Correction calculator
« Reply #175 on: February 26, 2018, 02:33:39 AM »
I have a new set of precision Plato saccharometers arriving tomorrow.   Over time I will try to provide you guys some more data.  Will confirm my correction factor and post any measurements on this thread.

EDIT Perhaps it would be more helpful if I just posted raw data for batches where available:  OG,  mid, and FG  WRI  and saccharometer readings.  Let me know if it would be of any use.

Give me all of the data!
Will do.  Brewed Pils yesterday, will probably get a mid fermentation reading mid week, FG by next week.  I'll post a batch of data then. These pro brewery saccharometers are very easy to read; refractometer is an eye strain by comparison!  But I have confirmed the correction I've been using.
Rob
Akron, Ohio

"There is always a well-known solution to every human problem -- neat, plausible, and wrong."  -- Mencken

Il meglio è nemico del bene.

De gustibus non est disputandum.

Non illegitimes carborundum.

Offline hackrsackr

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Re: Improved Refractometer Correction calculator
« Reply #176 on: February 26, 2018, 04:45:43 AM »
I have a new set of precision Plato saccharometers arriving tomorrow.   Over time I will try to provide you guys some more data.  Will confirm my correction factor and post any measurements on this thread.

EDIT Perhaps it would be more helpful if I just posted raw data for batches where available:  OG,  mid, and FG  WRI  and saccharometer readings.  Let me know if it would be of any use.

Give me all of the data!
Will do.  Brewed Pils yesterday, will probably get a mid fermentation reading mid week, FG by next week.  I'll post a batch of data then. These pro brewery saccharometers are very easy to read; refractometer is an eye strain by comparison!  But I have confirmed the correction I've been using.

Link to the saccharometers?


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Offline Robert

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Re: Improved Refractometer Correction calculator
« Reply #177 on: February 26, 2018, 05:20:53 AM »
^^^^
Here's the link.

Brix Saccharometer (7.5-16) https://www.amazon.com/dp/B01H3X2NUG/ref=cm_sw_r_cp_apap_OiXfhDZFmyj7T

  It may just give you one, but look down to "frequently bought together. "   There's a deal on the 0°-8.5°P and 7.5°-16°P; above that is, for most of us, mash density where we want to use a refractometer,  but they have one more at higher range if you keep searching.  This is a high grade professional brewery instrument. No buyer's remorse at all.

EDIT  Just a point of information,  you need a 14" test jar and a ~175-200ml sample.

Further point of info: these are marked at gradations of 0.1°P and there is a built in thermometer and correction scale, of course.
« Last Edit: February 26, 2018, 05:36:08 AM by Robert »
Rob
Akron, Ohio

"There is always a well-known solution to every human problem -- neat, plausible, and wrong."  -- Mencken

Il meglio è nemico del bene.

De gustibus non est disputandum.

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Offline hackrsackr

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Re: Improved Refractometer Correction calculator
« Reply #178 on: February 26, 2018, 05:29:17 AM »
^^^^
Here's the link.

Brix Saccharometer (7.5-16) https://www.amazon.com/dp/B01H3X2NUG/ref=cm_sw_r_cp_apap_OiXfhDZFmyj7T

  It may just give you one, but look down to "frequently bought together. "   There's a deal on the 0°-8.5°P and 7.5°-16°P; above that is, for most of us, mash density where we want to use a refractometer,  but they have one more at higher range if you keep searching.  This is a high grade professional brewery instrument. No buyer's remorse at all.
Awesome! Thanks, Robert.


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Offline Petr

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Re: Improved Refractometer Correction calculator
« Reply #179 on: March 01, 2018, 12:49:47 AM »
I would just like to mention that the main benefit of my formulae is that it does work for fermenting wort. For the well-attenuated beer, Terrill's and my result aren't too different. I would say they're within an experimental error.