Hey guys, so sorry for the late reply here, very busy lately.
Originally Posted by zzARzz
I'm not sure if you've already done this, but it may be a case where you need to calibrate both thermometers in boiling water (adjust them until they read the water boiling point for your elevation, since you're in CO). If the mashtun thermometer is removable there is usually a nut beneath the dial that the stem comes out of. A small wrench will allow you to calibrate the reading to your boiling point once you submerge it in the boiling water.
Calibrating the digital one to match your analog should at least eliminate any suspected variance due to your equipment.
When I mash in I take 5 readings from different areas in the bed and if there are large differences between them (i.e. hot/cold pockets) I'll stir it really well until they're within a couple of degrees of each other, then seal it up.
I had not considered attempting to calibrate...actually I didn't even know that was a possibility. I'll definitely look into doing so though.
Originally Posted by cluckk
After you stir are you giving a rest to allow the temperatures to stabilize before checking temperature? After the stir there will be pockets of higher and lower temperatures. Let everything sit for a couple minutes before checking the temperature. Also, if you add heat it will take a couple minutes, even after the heat is cut off, for the temps to stabilize. The bottom will get hotter faster and that grain will have to exchange heat with other grain, even if you stir it.
The difference between thermometers is a different problem. Have you tried boiling plain water to see which reads closer to 212F (100C)? I have two probe thermometers. One came with my burner and the other I bought at my LHBS. The one that came with my fryer is regularly 10-15F lower than the other and reads a full boil as being 200F or so. Needless to say I don't use this one for the mash.
I wasn't totally sure what I should be doing in terms of stirring and trying to get an accurate reading. When I was doing my last mash I tired to sort of shove the thermometer down into the grain bed with the stirring spoon in order to try and get a more realistic reading. I'd let it sit there and everything seemed fine. However, after I'd stir it I'd see a huge spike in temp which gave me cause for concern that I might be overheating the mash. I'd kick the heat down a bit stir as much as possible then stick the probe back in and the temp seemed to level off. However I'd have to repeat this process every 10-15 minutes when I stirred and the spikes in temperature gave me cause for concern. I'm trying to find a way to get the right, constant amount of heat without such spikes.
I also have not attempted to test or calibrate the different thermometers yet based on my location. I'm guessing that I should probably do so. I'm also considering buying a new digital probe thermometer as the one I have is somewhat crappy and doesn't work well with the receiver that I have (allowing my to monitor temp without being near the mash if needed). Do you guys have any suggestions on a solid thermometer that you like to use?