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specific gravity - refractometer

PostPosted: Mon Feb 21, 2011 8:52 am
by jimmiec
This weekend I used one of the new refractometers with the specific gravity scale. It looks like its accuracy is OK for lower specific gravities ( < 1.040) but not for higher gravities, according to <a href="">Morebeer</a>. This weekend, the refractometer was reading an OG of 1.076 with a brix of ~20.2. From the Morebeer spreadsheet, the calculated OG is 1.084. Could we confirm the accuracy of the refractometer (with specific gravity) and spreadsheet with a hydrometer sometime? I don't have an hydrometer anymore.

PostPosted: Mon Feb 21, 2011 5:43 pm
by yeastmeister
Yep, I will try soon. I checked the spreadsheet, promash, and beersmith. All gave a slightly different output. Both beersmith and promash include a refractometer calibrating. I see their default is different, so that may be why they are different. But neither of them came out as high as the spreadsheet.

PostPosted: Tue Feb 22, 2011 6:25 am
by yeastmeister
Ok, it appears as though both promash and beersmith agree once you set their refractometer calibration parameters the same. Apparently, each program comes with a slightly different default calibration.

Obviously, the spreadsheet is doing the same by entering in the calibration equation they came up with for their specific refractometer. Each one will be slightly different.

So, while the spreadsheet is an approximation, you can use either promash, or beersmith, follow their directions on refractometer calibrations, and make a calibration for your specific refractometer.

So, for 20.2 brix, the spreadsheet gives 1.084, whereas both beersmith and promash give between 1.080 and 1.082 depending on their default calibrations.

Keep in mind that hydrometers are doing the same thing. Just approximating. I haven't really seen many "precision" hydrometers for that level of brix. Most of the precision ones I have seen are for near the terminal gravity range.

The only actual way to measure specific gravity is with a good high quality milligram scale and a Pycnometer. I have the equipment to do it correctly, but its just so much easier to take a refractometer reading and use that.
Image from Wikipedia

PostPosted: Wed Feb 23, 2011 4:35 pm
by aleguy
Damn B3!!! They should have built the correction into the scale on the refractometer instead of making you go to a spreadsheet program. I was thinking about buying one until I found out they crapped out. Might just as well get a normal refractometer if I have to use a computer program anyway. Much cheaper. Why pay more for something as useless as that??? :evil:

PostPosted: Wed Feb 23, 2011 4:39 pm
by jimmiec
Morebeer is working with the makers to have it corrected and said they would be the first to have it available sometime in 2011.