How can I calibrate the 2nd thermometer?
What I personally do, is take a plastic or styrofoam cup, fill it half way with water and put it in the freezer until it freezes solid. Then I take it out and leave it on my counter for an hour (+\-) or so until some of it melts enough to submerge the thermometer. Swirl the thermometer around for a minute and it should read 32 degrees. If it doesn't read 32, then you know it's off by how ever much it's reading. Because the true temp is exactly 32 degrees.