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Old 12-05-2010, 03:30 PM   #1
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Default Digital refractometer

Found this while looking for a ph meter.

http://www.milwaukeetesters.com/MA871.html

Anyone using it? How you like it?



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Old 12-05-2010, 03:56 PM   #2
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How much is it?
Cannot find any pricing for their products.



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Old 12-05-2010, 04:04 PM   #3
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I just did a Bing shopping search and they can cost anywhere from a few hundred to thousands of dollars.

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Old 12-05-2010, 04:31 PM   #4
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The one I listed cost $110

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Old 12-10-2010, 04:11 PM   #5
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Anyone using this?
I'm about to get one but concerned how it reads high lovibond samples.

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Old 12-11-2010, 01:20 AM   #6
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That's one of the advantages of the digital design. The light never actually enters the sample. It is reflected off it. But even in the transmission (Abbe) design the film of beer/wort is very thin. A beer of 127 SRM exhibits absorption (at 430 nm - blue) of 10 A in 1 cm. In a 1 mm path, it is 1 A, in a 0.5 nm path, 0.5 A etc. But refractometers measure at 589 nm (yellow sodium line) where the absorptions will be about 1/5th of the 430 nm values.

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Old 12-11-2010, 03:17 AM   #7
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Quote:
Originally Posted by ajdelange View Post
That's one of the advantages of the digital design. The light never actually enters the sample. It is reflected off it. But even in the transmission (Abbe) design the film of beer/wort is very thin. A beer of 127 SRM exhibits absorption (at 430 nm - blue) of 10 A in 1 cm. In a 1 mm path, it is 1 A, in a 0.5 nm path, 0.5 A etc. But refractometers measure at 589 nm (yellow sodium line) where the absorptions will be about 1/5th of the 430 nm values.
Ok, translating it, it is accurate regardless the lovibond?
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Old 12-11-2010, 03:27 AM   #8
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It should accurately measure refractive index. Whether the refractive index of a highly colored (or any other, for that matter) beer is close to the refractive index of a sucrose solution (what the instrument is calibrated for) of equal sugar content is another question. In general, it seems to work. Sometimes it can be off by 1 Bx or more. That's why I don't think refractometers are good for much beyond monitoring runoff during sparging.

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Old 12-12-2010, 05:54 AM   #9
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Quote:
Originally Posted by ajdelange View Post
It should accurately measure refractive index. Whether the refractive index of a highly colored (or any other, for that matter) beer is close to the refractive index of a sucrose solution (what the instrument is calibrated for) of equal sugar content is another question. In general, it seems to work. Sometimes it can be off by 1 Bx or more. That's why I don't think refractometers are good for much beyond monitoring runoff during sparging.
So do you have one or have used one before?

I like the idea of using one because it gives a number and I don't have to try to stare at a little scale. I'll chart my fermentations to see see how they are coming along but when they're done I'll verify by hydrometer. After compensating for temperature and the individual hydrometer's calibration, the results are right on.
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Old 12-12-2010, 06:41 AM   #10
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Quote:
Originally Posted by Bigscience View Post
So do you have one or have used one before?
How would I know they can be off by a Bx or more if I didn't have one?

Quote:
Originally Posted by Bigscience View Post
I like the idea of using one because it gives a number and I don't have to try to stare at a little scale. I'll chart my fermentations to see see how they are coming along but when they're done I'll verify by hydrometer.
I like the idea too. That's why I got a couple and started checking them out against hydrometer and density meter. I didn't find the agreement that good. Unfortunately I'm overseas at the moment and can't look at my notes or I'd be more specific.

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After compensating for temperature and the individual hydrometer's calibration, the results are right on.
Post fermentation it's necessary to correct for alcohol content so I assume that you are doing that as well. There are several spreadsheets about that will do this for you (e.g the one from MoreBeer which corrects for alcohol and temperature based on original refractometer reading).

One thing I do remember in particular is that the refractive index of beer and the refractive index of sucrose solutions do not change with temperature at the same rate so refractometer ATC, based on sucrose, isn't going to work very well.

Refractometers are, of course, great for monitoring progress of sparging or fermentation. Beyond that, I'm not too keen on them.


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