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December 14th, 2016, 08:18 PM   #1
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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.
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December 14th, 2016, 08:38 PM   #2
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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

$Brix =((143.254 \text{sg}-648.67) \text{sg}+1125.81) \text{sg}-620.389$
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December 19th, 2016, 08:38 PM   #3
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Brix Calculations

Quote:
Originally Posted by romsek View Post
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?
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December 20th, 2016, 09:34 PM   #4
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Quote:
Originally Posted by AshBox View Post
So I have to use this equation?
if you want to replicate the expression in method 1 yes.
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December 21st, 2016, 08:49 PM   #5
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Brix Calclation

Quote:
Originally Posted by AshBox View Post
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`
Thanks from AshBox
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