I am prepping for my first brew in 10 months. I expect to make some mistakes and run into some speed bumps, so I'm doing most of the prep a day in advance. One thing I decided to do is check the calibration of my refractometer, hydrometer, and thermapen. The thermapen and refractometer needed essentially no adjustment. The hydrometer was a bit off.
I sampled distilled water at 68*F. My hydrometer claims to be calibrated for 60*F. It read 1.003 and according to the beersmith adjustment it should read 0.999.
Now I could just subtract 0.004 from any reading, but it also occurred to me that I could just find out what temp my hydrometer is really calibrated for and enter that into beersmith.
To do this, I put my hydrometer in warm water and saw a reading below 1.000 as expected. I allowed the water to cool until the hydrometer read 1.000, and used my thermapen to learn that my hydrometer is calibrated for about 89*F. I was able to verify this using beersmith by entering a measured gravity of 1.003 at 68*F and adjusting the calibration temp until the actual gravity read 1.000. This occurred between 87*F and 91*F.