The best (most accurate) candy/fry thermometers are wet bulb types - they don't have to be calibrated. Digital or dial type need to be calibrated ... and "infra" will give you the "surface" temperature - not the temp under the surface.
Another nice thing is that they are also fairly cheap.
"It ain't what you don't know that gets you in trouble. It's what you know for sure that just ain't so." - Mark Twain
I have both a wet bulb and a dial type. I prefer the my dial type Taylor because it has an 18" probe, takes up less room in the pot and is easier to read. I've seen some complaints about the lettering coming off some of the paddle type wet bulbs. My mercury wet bulb is over 30 years old and has the lettering inside of a glass tube. Because of condensation problems i had to dry out and reseal the glass tube about 2 years ago and that's when I decided to spring for the Taylor long probe dial type.