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Old 08-07-2011, 09:22 PM   #1
BeezBrew
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Oct 2008
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I've been having issues with gravity readings using my refractometer and hydrometer. They both seem to be off by at least 5 gravity points which i find unacceptable. So i decided to make a reference solution by adding 1/4 lb of table sugar to a pint (1/8 gallon) of water and measured the gravity. Theoretically, the gravity of this reference solution should be 1.092 (correct me if i'm wrong, went by the ppg of table sugar in John Palmer's book).

The hydrometer measured 1.092 on the dot at 80F while my refractometer measured 1.078. WTF? Both my hydrometer and refractometer read 0 with both distilled water and tap water. Is my refractometer broken, or am i missing something?
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Old 08-07-2011, 11:07 PM   #2
Kaz
 
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Are their scales calibrated at the same temperature, or more likely, the refractometer is temperature compensating and the hydrometer is calibrated at 60F Are you measure the gravity at the hydrometers' temp?
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Old 08-08-2011, 12:37 AM   #3
BeezBrew
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Both are calibrated to the same temperature. I read both at ambient temp. in my apartment, which right now is around 80 degrees. I just don't understand why the refractometer is off so much. The model number is RSG-100/ATC which means it has a temperature compensation component. So i'm not sure temperature would even be a factor as along as it within the 10-30 degrees celcius range.
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Old 08-08-2011, 03:05 AM   #4
Rolly
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Not sure if it helps, but I just posted an identical thread earlier today because I'm having this exact problem with exactly the same refractometer (same model number). Both the hydrometer and refractometer read 1.00 gravity in distilled water. but when I'm measuring wort the refractometer is close to 5 gravity points lower than the hydrometer.

Maybe we got a bad batch of refractometers, because I've always heard they were a lifesaver, but so far for me it's just a PITA.

 
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Old 08-08-2011, 04:17 AM   #5
BeezBrew
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Good to hear i'm not the only one. I received mine as a gift last X-mas, so not sure what their return policy is or if its even possible. I'm kind of tired of trying to figure it out.
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Old 08-08-2011, 09:06 PM   #6
RoadKing
 
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Try using the Brix scale and use Beersmith or a spread sheet to convert it.
It seems the Specific gravity scale is skewed especially at higher SG"s
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Old 08-08-2011, 11:01 PM   #7
Malticulous
 
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I've come to the conclusion that the refractometer has no place in my brewery. There was another thread not too long ago...
http://www.homebrewtalk.com/f128/hyd...5/#post3132856

I'm tempted to calibrate mine with a 1.050 sugar solution.
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Old 08-08-2011, 11:09 PM   #8
Beezy
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The more I hear the more I don't want. I am getting great eff so I just extract a tad more wort than I need for my pre-boil and SG. For the FG test, I do one after a week and half or two weeks and I like to taste the sample so I don't feel as I waste any wort. Hydrometers are cheap, they work. Spend my money on something better.

 
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