analysis gravity readings

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analysis gravity readings

Postby balikian » Wed Nov 07, 2007 3:30 am

How do I do the gravity readings in the analysis section. I must be doing something wrong. If I use a refractometer and I take an original reading of 13.5 and a final reading of 6.5, the analysis section says I have a 3.82 ABV, which isn't right. The correct ABV is 6% according to this spreadsheet at morebeer:

http://morebeer.com/public/beer/refractbeer.xls

I must be not setting something to take into account the alcohol in the beer. I would rather use just one tool rather than use that spreadsheet along with Beer Tools.

What am I doing wrong?

cheers!

scott
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RE: gravity readings

Postby wottaguy » Wed Nov 07, 2007 6:45 am

Hello balikian,

Have you tried to use the calculator for % Atrtenuation by going to the menu item Window/Calculators/5 Atten? I have tried it and it seemsto work good.

Hope this helps!

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Postby balikian » Wed Nov 07, 2007 11:31 am

Gives me the same value in there. I am entering an OG of 13.5 and a TG of 6.5 and getting 3.82% That is not right. Is there some constant or something I am supposed to fiddle with? Like enter my values, get the wrong ABV and then set the ABV to what it should be and figure out what I am supposed to adjust things by? That seems weird. Is this maybe fixed in the updated version of this tool? I didn't see anything in the version news bit.
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Converting refractometer readings with BeerTools Pro

Postby jeff » Wed Nov 07, 2007 11:55 am

balikian wrote:Gives me the same value in there. I am entering an OG of 13.5 and a TG of 6.5 and getting 3.82% That is not right. Is there some constant or something I am supposed to fiddle with? Like enter my values, get the wrong ABV and then set the ABV to what it should be and figure out what I am supposed to adjust things by? That seems weird. Is this maybe fixed in the updated version of this tool? I didn't see anything in the version news bit.


The spreadsheet you are referring to uses refractometer brix measurements. In order to calculate your ABV you must first enter your measurements in the Calculators->S.G.->Refractometer calculator. When I enter your brix measurements, the calculator determines your real OG to be 13.17 Plato and TG to be 2.0 Plato. Then plugging these values in the Calculators->%Atten. calculator the ABV is calculated as 5.97%.

The refractometer is a great tool, but it isn't the most accurate choice for measuring terminal gravity because of the effect alcohol has on the readings. It does fine for measuring OG because there is no alcohol in the wort. With that in mind, perhaps you can measure your OG with the refractometer but measure your TG with a standard hydrometer for the most accurate result.
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Postby balikian » Wed Nov 07, 2007 2:46 pm

Thanks Jeff. I was actually going to plan on doing that and someone suggested to keep using it but just make sure the calculations took into account the alcohol for TG. I was reading on More Beer about how to use the refractometer cause the whole TG thing has been bugging me and noticed they had a spreadsheet. Not really understanding the math behind it all (and not really wanting to, I guess) I'm not clear if that spreadsheet takes the alcohol into account. It claims to.

Then the other thing was everything I'd been reading kept saying that brix and plato were virtually identical. Even the history of those scales I read made it seem that the difference was negligible. I'll have to play around with your suggestion of converting brix to plato first and then entering in those numbers.

I'm really happy with this software. You can use as much as you want of it and there seems to be a lot more available as you dig deeper. thanks for the help.
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Postby jeff » Wed Nov 07, 2007 3:23 pm

balikian wrote:Then the other thing was everything I'd been reading kept saying that brix and plato were virtually identical. Even the history of those scales I read made it seem that the difference was negligible. I'll have to play around with your suggestion of converting brix to plato first and then entering in those numbers.


Brix and Plato values pretty close, but only before fermentation begins. Once fermentation begins the presence of alcohol renders the brix measurement inaccurate. The refractometer calculator in BTP helps approximate the actual gravity from the brix reading. For most purposes, the approximation is probably fine for home brewers; but the hydrometer will typically be closer to the truth.
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