# Thermometer Calibration

Howdy all,

So I just got this NIST-certified thermometer
http://www.arborsci.com/digital-thermometer
in the mail and I used it to check the crappy TruTemp thermometer I’ve been using to brew. Turns out, the TruTemp thermometer reads 7 - 8 degrees higher than certified thermometer across the mash range and at mash out temps.

Now, the TruTemp doesn’t provide an instant read, but it does give a reading significantly faster than the certified thermometer, so I decided to try calibrating it. To do this, I heated up some water to above 172 (as per the certified thermometer), put both thermometer stems in the water at the same location (within a centimeter at most), then recorded the TruTemp reading as the certified reading passed through 172, 170, 158, 156, 154, 152, 150, and 148. I then repeated the process two more times.

Does this seem like a reasonable way to calibrate, and is reasonable consistency across three make-shift tests sufficient to consider the adjusted TruTemp readings to be reliable?

Either way, I’m psyched to discover how off my thermometer has been, as I have been making quite enjoyable beer even though I’ve been mashing in the 140 - 148 range all this time . It also explains why I’ve almost never been able to get my FGs above 1.010 ever since I switched to all grain.

Sounds like you did a good job of testing your thermometer.

How much faster are you talking about? Hard to pin down a time savings that would be worth the less-accurate reading, but I wouldn’t sacrifice a solid measurement for 10 seconds saved.

Awesome, thanks Nighthawk. Seemed like a reasonable approach, just wanted to get the reaction of some more experienced brewers.

Shade, the more accurate thermometer takes no more than 10 extra seconds to give a reading…probably less. I’m thinking 15 - 20 seconds isn’t sufficient time to anything close a full degree from something with the volume of a mash. I might try both for a few rounds and see how things track. The TruTemp is more convenient because I can dangle the probe in and don’t have to hold it until it reads like I do with the lollipop.

I just got this bad boy:

http://www.thermoworks.com/products/low ... 301wa.html

Cheap and adjustable calibration. All of my beers seem to dry out more than anticipated so I’m starting to think my crappy thermometer was reading incorrectly. I checked in a cup of ice water last night and it read perfectly at 32F.

FWIW, my TruTemp thermometer read perfectly at boiling and near perfectly at freezing…but was way off where it matters for brewing (148 - 170).

If your current thermometer was reading like mine (i.e., significantly higher than the actual temp), then yeah, it would definitely lead to drier and thinner beer beer. Really hoping I’ll be able to really control that aspect now…it’s the last frontier before I start experimenting more heavily with subtle variations in grain bills and hop schedules.