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Old 06-27-2006, 11:19 PM   #1
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Default Temp Correction Formula for Hydrometer

Does anyone have a temperature correction formula for hydrometer. I found this one but its not working when I check against the tables I've found.

=1.313454-0.132674*t+2.057793*2.71828-3*t*2-2.627634*2.71828-6*t*3

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Old 06-27-2006, 11:28 PM   #2
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This one works but is only accurate from 59 to 167F

=-2.52-0.0252*t+0.00112*t^2

The one I posted first is supposed to be accurate way above that.

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Old 06-27-2006, 11:43 PM   #3
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Here ya go- quick, easy, and no math!

http://hbd.org/cgi-bin/recipator/rec...ydrometer.html

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Old 06-27-2006, 11:48 PM   #4
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I was begining to think that this thread needed to go into an "Advanced Techniques" section of the forum.

/I think I finally beat HB99 with the smart a$$ comment.

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Old 06-28-2006, 12:01 AM   #5
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Thanks but I'm trying to put it in a spreadsheet so I need the equation. But it doesn't matter because my hydrometer only goes down to .99 which means I can only test wort at about 120F anyway. Though the correction isn't that big so I guess I could get pretty close at 170F.

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Old 06-28-2006, 01:07 AM   #6
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There is a formula in Papazian's book, but I'm not sure where my copy is right now. If I find it I will post it.

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Old 06-28-2006, 02:27 AM   #7
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Quote:
Originally Posted by jcarson83
Does anyone have a temperature correction formula for hydrometer. I found this one but its not working when I check against the tables I've found.

=1.313454-0.132674*t+2.057793*2.71828-3*t*2-2.627634*2.71828-6*t*3
Maybe you just typed the wrong thing, but that should be:

=1.313454-0.132674*t+2.057793*2.71828-3*t^2-2.627634*2.71828-6*t^3

where ^ means "to the power of"

Other than that, I really have no idea what the above means. What is t? Do you add the above result to what you actually read? I don't get it...
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Old 06-28-2006, 12:05 PM   #8
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t is Temperature. Yes you add the result to your reading. As the wort increases in temp it becomes less dense so unless it is cooler than 59F the result will be a positive number. The longer equation is supposed to allow you to correct results at higher temperatures.

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Old 06-29-2006, 04:19 AM   #9
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Okay. I guess it's fairly useless to me without converting, as we use Celcius here in Oz!

I have a maths degree, and I find something a bit strange about the two formulae. Are you sure that the 't' you use isn't measured from some temperature other than zero in one or both of the formulae?

The reason I ask is that it doesn't make sense to have completely different numbers in a formula that is supposed to be accurate to higher temps. The first few terms should be the same; it should just have some higher-order terms (terms proportional to t^4, t^5 etc.)

In fact, looking back at your original formula, it seems really strange as written. Perhaps try typing it out again? For example
-2.627634*2.71828-6*t^3 to me means:

-(2.627634*2.71828) - (6*t^3)

That seems weird. Why aren't all the constant terms just incorporated together?

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Old 06-29-2006, 11:47 AM   #10
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Quote:
Originally Posted by Brewsmith
I was begining to think that this thread needed to go into an "Advanced Techniques" section of the forum.

/I think I finally beat HB99 with the smart a$$ comment.
Ya got me there BS! Too much math in this post to get interested...I just add +1 or +2 and I'm done. Can't see all the fuss about large formula's when it's not necessary.

My chemistry is simple too! H2O is water and K9P comes from a dog.

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Keep It Simple Smarta$$!!
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