« on: November 26, 2014, 05:51:48 PM »
As a an engineer who had to calibrate his transducers every day, I have a comment on refractometer calibration.
Using your water of choice, distilled is often recommended, use that and set to zero Brix. You have zeroed the instrument. What about the gain? For a refractometer, you can check a 10% sugar solution (~1.040) by mixing water and sucrose, instructions are on the net. You might be surprised that the reading is off, I was. Then I tried 15 Brix and it was dead on. Diluted that to 10%, and it was off the same amount.
Adjusting the zero does not give you the gain (slope), and checking the gain at multiple points will show you if your instrument in linear. One learns this from every day practice over the years (until you are no longer doing hands on work).