Cheaper Refractometer Correction?

[cdrew23]

I am looking at getting a modestly priced refractometer, and came across this listing on homebrewfinds -

http://www.ebay.com/itm/RSG-100ATC-Black-Brix-Beer-Sugar-Wine-Wort-SG-0-32-Refractometer-SOFTCASE-/220976517877?pt=LH_DefaultDomain_0&hash=item33733a12f5

It states in the description that at higher gravity readings, the brix and SG scales do not correspond.

I was curious if anyone knows of a reliable method to correct this refractometer for higher gravity readings? Is the Brix scale accurate and the SG scale off or do they both become skewed at higher gravities?

Any help would be greatly appreciated - thanks
Drew

 

[BrewKnurd]

Well, according to the disclaimer, the SG scale is calculated based on SG = 1 + 0.004*Brix, which is a simplification. If that's the only source of error, then you could just take the Brix and use a more accurate formula: SG = (Brix / (258.6-((Brix / 258.2)*227.1))) + 1

But the other thing to keep in mind with refractometers is they are designed to measure the concentration of sucrose. Given that wort is not a pure sucrose solution (not even close), there will also be differences between the Brix reading you would get with a hydrometer and a refractometer.