So I'm getting ready for a double-batch brew day on Friday, and since the brew shop is closed today I decided to do some of the little things I've been meaning to do. I just got my hands on a Johnson controller, plus I have a digital probe thermometer I wanted to play with, so I got them together along with the analog dial thermometer I've been using since Day 1 (about 16 months ago). Boiled some water, put in the dial thermo, and it was reading 211F just like I expected . . . but the Johnson and my other probe both read 207. Since I'm at 3500 feet, it finally occurred to me to try to look up how much of a difference there might be between my boiling point and sea level.
As it turns out, water here SHOULD be boiling around 205F-207F, depending on the barometric pressure. In this case, I'm trusting my digital probes over the dial thermometer, and I calibrated it accordingly.
Of course, this also means I've been mashing up to 5 degrees cooler than I thought I was, striking and sparging with slightly lower temps than I wanted, and maybe even fermenting my last batch at 60F instead of 65F. It's better this way than being hotter than I thought, but hopefully I'll be even better off now.