You’ll notice over time that I never shut up about digital thermometers. I love them. I have a bunch of them. I don’t think any cook (indoor or outdoor) should be without one. And don’t rely on the crappy dial things most manufacturers install in the lids of their smokers. First off, they are typically wildly inaccurate and inconsistent. Secondly, you have no way to check them. Trust me, go with a digital.
I always say that if you aren’t using a thermometer, you’re just guessing.
I still stand by that, but what if your thermometer isn’t accurate? Aren’t you still guessing at that point?
It’s a valid point. If you don’t know whether or not your thermometer is telling you the truth, you’re still guessing.
That’s why it’s important to check your thermometers regularly. By regularly I mean twice per year or so. It’s easy to do, it’s fairly quick, and then you KNOW if your thermometer is working properly or not.
I always recommend owning two thermometers: 1.) A probe thermometer that will allow you to monitor pit temperature as well as the internal temperature of the meat you’re cooking, like this…my current favorite:
2.) An instant-read thermometer to get nearly-instant temperature readings for when you’re cooking at higher temperatures and things change more quickly, like this here:
Before I get into the tests, I also want to let you in on a little secret. Although I keep using the word accurate, it really doesn’t matter if your thermometer is accurate. It really doesn’t. If you test out your thermometer and it reads 10 degrees high, fear not. Run the test a few more times. Did it read 10 degrees high each time? If so, you’re fine. You don’t need your thermometers to be accurate…you need them to be consistent.
Essentially, it doesn’t matter if your thermometer is 10 degrees (or more) off, as long as it’s always 10 degrees off. Then you can adjust accordingly. Just fold a small tag like a piece of duct tape or something around the base where the probe plugs into the thermometer (or on the body of the thermometer if it’s an instant-read) and write (+10) on it. This way you know that particular thermometer reads 10 degrees high. Do this for all of your thermometers that are off, even by one or two degrees.
If you’re cooking chicken breasts and you want to pull them off the heat at 165 degrees F, and you’re using a thermometer that reads +10 degrees high, you’ll know to pull the chicken when your thermometer reads 175 degrees F. Make sense?
Okay then, on to the tests.
Yes, tests. Plural. There are two tests I do, one hot and one cold. You can do one or the other, but I like to do both, since they’re on opposite ends of the spectrum.
All these tests do is supply you with a known value to measure off of. In the first test, you’re going to use your thermometer to get a reading of boiling water. In the second test, you’re going to use your thermometer to get a reading of freezing water. Before you begin these tests, make sure you know at what temperature water boils and freezes at where you live.
If you live at sea level, water boils at 212 degrees F and freezes at 32 degrees F. If you live at higher altitudes, the atmospheric pressure is lower, and the temperature at which water boils is also lower. If you live below sea level, the atmospheric pressure is higher, resulting in a higher boiling temperature. You will find that the freezing point of water remains mostly constant, except in extreme circumstances. Here’s a nifty calculator that will tell you the boiling point of water for your location:
So there, now you have your known values. Now you can begin your tests.
*Please note – I prefer to use a pot to boil water as opposed to using a microwave. I’m not the most science-y of folks, but I know that superheating CAN occur when heating water in a microwave. Superheating is a phenomenon in which a liquid is heated beyond it’s boiling point without actually boiling. It goes over my head and I don’t fully get it, but I know that it can happen, so I avoid it to eliminate the chance. Plus, when you do it in the microwave, the temps will begin to fall once you pull it out of the microwave, which will affect your readings, especially if you’re testing multiple thermometers.
My advice is to stick with the old pot and water method. Once the water begins to boil, the water begins its transition to steam, and the temperature stops rising.
*Second note – If you’re going to perform both tests, don’t do them one right after the other. Allow the thermometer time to return to room temperature before performing the next test. Metal probes will retain heat and/or cold for a bit and going directly from boiling water to freezing water (or vice versa) will affect your readings. And it will probably damage the probe.
Okay, so now we can begin the tests:
Test 1 – Put some water into a small pot, bring it to a boil, and place your thermometer in the water (don’t let the tip of the thermometer hit the sides or bottom of the pot), leaving it there until you get a stable reading. It should read 212 degrees F (or whatever the boiling temperature is for water where you live). Make a note of the reading for that particular thermometer and mark it appropriately. Repeat for each thermometer that you use.
Test 2 – Fill a glass with ice cubes and then top it off with cold water. Give it a stir for a few seconds, and then let it sit for 3-5 minutes. Give it another stir, then insert your thermometer into the glass, once again being careful to not touch the sides or bottom of the glass. The temperature should read 32 degrees F. Record the difference and mark your thermometer appropriately. Repeat for each thermometer that you use.
Some of the higher end thermometers will allow themselves to be calibrated, where you can adjust the thermometer to the known reading if it’s off. Most consumer-grade thermometers don’t have this capability though, although that’s perfectly fine. As I said above, the accuracy doesn’t matter as much as the consistency.
If you’re testing a new thermometer, I recommend performing the tests multiple times to ensure that it’s being consistent. Otherwise, just do this every six months or so, unless you suspect something has gone awry with one of your thermometers.
Thanks for reading!