Model: CDNDTTC $20 While CDN's DTQ450Q handheld digital is our absolute favorite thermometer for spot checking everything during brew day, this DTTC model is a close second and adds a LOT of extra features. First, let's get this out of the way immediately. As a thermometer it is VERY accurate, nearly on par with the pricey Thermapen (see test results). It comes with a long stainless probe on a cord so that the controls/display can be in a more convenient location. It also features a clock, timer, and our favorite feature; high and low temperature alarms.
These thermometers are from my newest and ongoing supplier after carefully evaluating several different brands. These are a great value for the features you get. The most important feature is the recalibration screw on the back so you can tailor the thermometer to be most accurate in the temp range you care most about. They are all stainless and have a glass window for heat tolerance. I have both 2" face and 3" face thermometers depending on your application and I can make them weldless also. See details for more information.
If you want to insert a narrow digital thermometer probe into a a hole in your vessel, a threaded fitting such as a tee or a coupling welded into your vessel, here's how to do it. This fitting has 1/2" OR 1/4 male NPT on one end and will accept up to a .25" diameter probe (see notes). The included orings make a leak free connection. You can also get this as a weldless setup. See more info for application pictures, etc.
Model: CDN - $17 I sell kits with bimetal dial thermometers because people like to install them, but I always recommend to spot check your temps with a more accurate, quick reading digital thermometer like this one prior to walking away from a mash. I've tried half a dozen instant read thermometers and this is by far my favorite. Waterproof, Recalibratable, 5 year warranty, and under 20 bucks! As of April 2012, these units have an improved narrow tip that reads even faster.