a meat thermometer touchs the bottom of the pan so it reads the temp of the pan, a candy thermometer is suspended in the liquid and reads the temp better.
Things I learned about making yogurt:
1) candy thermometers are hard to find and a meat thermometer does not work well.
2)milk will fry and fried milk does not taste good
3)fried milk is hard to get off of mom's good pans
4)if the milk is cool enough for the cat to drink out of the pan it is...