OK I'm getting pretty frustrated and could use some advice. I started out using the long metal probe dial thermometers and found that despite calibrating them they were too unreliable. Then I went to a glass, non mercury lab thermometer and I've been using that for a while believing it was pretty accurate. Well now I have some new Blichmann boilermakers and was just down in the kitchen trying to check their accuracy against the lab thermometer in some hot water and low and behold, they were both within 1 degree of each other all the way through the temp spectrum all the way to a full rolling boil maxing out at 219 deg F. So, I also bought a digital probe thermometer as a way to monitor my mash temp at the top of the mash in addition to the Blichmann dial thermometer which will be more towards the middle of the pot, and I thought it would be a good idea to see how it compared to the others. The Digital thermometer read about 4 degrees lower in the 160 degree range and a full seven degrees at boiling, registering exactly 212 at a full rolling boil. Obviously I don't really care about the boiling temp range but a 4 degree difference in the mashing range is in my view significant. Which of these darn things is right?!! Thanks.