Don't give up on that unit just yet. Focus for the time being on what it's good for rather than what you see now as its deficiencies. You'll learn to like it. I'm coming to the conclusion that most home brewers spend way too much time obsessing on "numbers" that, in the major scheme of things, should be better thought of as "goals" rather than "absolutes."
I confess. Guilty as charged, Your Honor!
As long as our numbers are somewhere in the right Zip code for the style we're brewing, does it really matter whether the brix is 13.3, 13.5, or 13.8? That converts to 1.054, 1.055, 1.056. Or looked at a different way, it's the measure of a single unit of scale on a hydrometer. And that assumes that your hydrometers are in fact properly calibrated, the sample is correctly measured at the calibration temperature, the hydrometer is floating freely and vertically in the sample jar and not adhering to the cylinder with hydrostatic friction and free of any gasses that may be 'floating' it above the true specific gravity. Additionally, are you able to see through the muck to clearly discern the meniscus, and if so are your eyes sharp enough to see where the meniscus touches tangentially to the graduated scale?
Like just about everyone else, it gives me great satisfaction to hit my numbers. It reinforces that what I'm doing is both predictable and repeatable, at least from an empirical measure. But if I can't taste the difference between the recipe I brewed last fall with the same one I brewed last week then why should I get all wrapped around the axle? Last year's Helles might have been (calculated) to be 5.4% ABV but this year it's 5.7% (calculated, once again!). RDWHAHB. Should it concern me if I can't taste the difference? Is the ATF gonna' crash through my front door and drag me away in chains? Can my ego survive the shame that, from a "numbers" standpoint, I'm an abject failure as an amateur brewer? As long as I'm not in another time zone and I fit within the style guidelines (if I'm even trying to meet style guidelines), then all is well within my world.
After dropping my manual refractometer that I'd used for at least 6 years for both wine making and beer brewing, I got the Milwaukee brix digital as a replacement last fall. I pull a 3~4ml sample of wort or must with a 5ml pipette and put it into a shot glass, so probably about 1/10th of the volume I'd need for a hydrometer cylinder. Then I agitate it by stirring rapidly with the pipette to dissipate any dissolved gasses, allow any solids to settle out and cool to 20C +/- 5C. I haven't actually measured the volume of the sample that fills the well of the unit, but it's probably right around 1ml, which is about what I'd use to flood the platen of my former hand held refractometer. I also found, by taking parallel readings with narrow range hydrometers, that the Milwaukee digital was at least as accurate as the hydrometers, which is to say +/- 0.2 SG unit measure (i.e., 1.044 ~ 1.046), even as it gives a value reading down to 0.1 degree brix, so I can't definitely say which is more accurate.
That said, with hydrometers the errors can come primarily from calibration, temperature and visual interpretation. With refractometers the principal errors would be calibration, temperature outside the range of ATC compensation, and the calculated value of specific gravity conversion from refractive index (RI) to SG. Since in the Milwaukee unit calibration is so simple and easy to automatically accomplish, and ATC is read directly from the sample temperature in the well, those possible data errors mostly non-existent. The variables in formulae that convert RI values to SG are understood and "baked in" to the math, so any inaccuracies would be mostly linear, consistent over any sample, and extremely minor relative to the possible sum of errors when using a hydrometer. Even the grossest of cumulative hydrometer errors aren't something we, as home brewers, need to be too concerned with, unless we:
"measure with a micrometer, mark with a grease pencil, cut with an axe, fit with a sledge."
If we needed the precision accuracy to replicate identical beers with every batch, we'd all hire a staff of chemists with a lab full of sophisticated (and very expensive) equipment. But we're HOME brewers, not professionals, and we're not trying to produce the same product with barely measurable differences consistently day in and day out. We're hobbyists who get a kick out of creating a variety of beers that are not only as good as what BMC cranks out, but even BETTER. We chase the illusive butterfly of replicating something on par with the local microbrewery we frequent with our beer loving friends. Even with the most sophisticated equipment setups, we'll never reach that level of Nirvana, but it sure is fun to try.
