A word of caution when using the infrared thermometers, they are "calibrated" based on "black body" emissions. In other words, if you are measuring the temperature of the asphalt in the parking lot, they are spot on. However, on highly reflective surfaces their accuracy can suffer.
I always check mine using a thermocouple as a reference. I check the thermocouple using boiling water. That doesn't vary too much unless you are at a very high altitude. That simply confirms the thermocouple is functioning properly.
Then I compare the temperature reading of the infrared thermometer with that obtained using the thermocouple. If they are within 20 degrees or so, that's good enough for work. After all, the minimum preheat is the minimum temperature. If the infrared reads too low, I just compensate for the error.
I use a RadioShack multimeter with a tong meter attachment for current and a thermal couple for temperature. It may have cost around $50. The infrared thermometer is a Ryobi. It seems to work fine. It wasn't that expensive.
Again, the infrared thermometer can provide erroneous readings on surfaces such as stainless, nickel, or aluminum. Black oxide such as that found on hot rolled steel are spot on.
Bob Wiswesser wrote a very good article on the subject for Inspection Trends a little more than a year ago. You can probably find it in the Inspection Trends archives if you visit the website.
Best regards - Al