Just as an experiment, I recently wanted to test the accuracy of home thermometers. I have one expensive digital, three with a dial of the top, and two with liquid in a glass tube. My results showed different readings on every one of them..and these were NOT cheap thermometers. Since I do several stage step mashing where accuracy is the key at each step, I now find myself wondering how many others may think they are dead on the numbers while actually being up to 7-10 degrees off. Any suggestions as to how to do a sanity check with a known temperature to calibrate them? Are there shops for such calibration? Maybe even, a thermometer that is guaranteed to be accurate and reliable?