As usual, bludawg has some sage advice.
I remember my early smokes. Had a a wireless digital thermometer, the one that came on the smoker, and a thermapen, and none of the numbers matched up. So I calibrated, I stressed out, I set alarms on the remote thermometer to wake me up multiple times in the middle of the night if temps got more than 20 degrees either way of 225, etc. So stressful and not anything that bbq should be.
You'll drive yourself crazy worrying about temps and how accurate the readings are. Remember, this is bbq, stuff that people have been doing practically forever without any technology whatsoever, not splitting the damn atom. If you have a clean fire, some heat, and some smoke, your meat will be done when it's done, and it will taste farking amazing.
Granted, technology has enabled us to achieve some sort of consistency with a little more ease, but the same can be said for just having practice. The more you smoke, the less you find yourself relying on thermometers, worry about how accurate they are, etc. You just start to realize that if you build a fire a certain way, cook something for about so long, and know what meat feels like when it's done, you'll still end up with a damn good end product even if there isn't a thermometer within 100 miles.
So, like others have said, calibrate one if you need to for a reasonable reference, and then just throw the meat on and have a few cold ones. The meat will still cook, and the less you worry about it, the better it will taste.