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 December 14th, 2016, 09:18 PM #1 Member     Joined: Oct 2016 From: labenon Posts: 33 Thanks: 4 Brix Calculations Can any one help me to solve this? I have been working on my spreadsheets and have reached a confusing cross road intersection regarding Brix calculation. This because there seems to be more than one way of calculating it with a resulting different answer. Method 1. Calculating °Brix from SG is based on an expression from a polynomial fit to a large data set: brix = 143.254 * sg3 - 648.670 * sg2 + 1125.805 * sg - 620.389 Method 2. Brix = (((182.4601 * SG -775.6821) * SG +1262.7794) * SG -669.5622) The error is in the decimals, though it may appear insignificant it has implications in other calculations which are derived from the Brix answer. I am getting confuse with decimals.
 December 14th, 2016, 09:38 PM #2 Senior Member     Joined: Sep 2015 From: CA Posts: 1,105 Thanks: 576 the two expressions are significantly different I've seen the idea behind method 2 used to reduce numerical error in evaluating polynomials but the numbers don't match up with the polynomial in method 1. what method two should look like is $Brix =((143.254 \text{sg}-648.67) \text{sg}+1125.81) \text{sg}-620.389$
December 19th, 2016, 09:38 PM   #3
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Brix Calculations

Quote:
 Originally Posted by romsek the two expressions are significantly different I've seen the idea behind method 2 used to reduce numerical error in evaluating polynomials but the numbers don't match up with the polynomial in method 1. what method two should look like is $Brix =((143.254 \text{sg}-648.67) \text{sg}+1125.81) \text{sg}-620.389$
So I have to use this equation?

December 20th, 2016, 10:34 PM   #4
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Quote:
 Originally Posted by AshBox So I have to use this equation?
if you want to replicate the expression in method 1 yes.

December 21st, 2016, 09:49 PM   #5
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Brix Calclation

Quote:
 Originally Posted by AshBox Can any one help me to solve this? I have been working on my spreadsheets and have reached a confusing cross road intersection regarding Brix calculation. This because there seems to be more than one way of calculating it with a resulting different answer. Method 1. Calculating °Brix from SG is based on an expression from a polynomial fit to a large data set: brix = 143.254 * sg3 - 648.670 * sg2 + 1125.805 * sg - 620.389 Method 2. Brix = (((182.4601 * SG -775.6821) * SG +1262.7794) * SG -669.5622) The error is in the decimals, though it may appear insignificant it has implications in other calculations which are derived from the Brix answer. I am getting confuse with decimals.

Hi, You can use this formula.

°Bx = (((182.4601*S -775.6821)*S +1262.7794)*S -669.5622)

Or I have also found this information, I hope it will help you somehow!

The Brix value can be obtained from the polynomial fit to the ICUMSA table: Bx = (((((11758.74*nD -88885.21)*nD + 270177.93)*nD - 413145.80)*nD + 318417.95)*nD -99127.4536) where nD is the refractive index, measured at the wavelength of the sodium D line (589.3 nm) at 20 °C`

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