Another part of the discussion at the IFSQN web site was on using IR Guns to measure the temperature. Following is one of my replies in regards to the issue:
IR thermometers are a great product if used correctly, but many people don’t know how to use them correctly.
They are not like lasers taking the temperature at a specific point. You do not point them at a spot and see the temperature at that spot. It is more like a flash light where the area it covers spreads out.
So imagine shining a flash light from your freezer door into the freezer and having half the room light up. That’s what you are measuring the temperature off with the infrared.
Cheaper ones have a much wider spread while the more expensive ones have a narrower beam. The narrower beam allows you to be more selective in what you are measuring (a single item or part of a a larger item) or be further away. But chances are the average user has no idea about this, stands a comfortable distance away and is measuring an item and half a dozen things around it.
They also have the risk of reflection with certain materials.
Like I said, great product if used correctly.