Available in a range of sizes and shapes and with a variety of features, when shopping for digital infrared thermometers there are numerous factors that you should keep in mind.
In very simple words, not all objects emit infrared energy equally. The type of surfaces and other factors can influence the amount of infrared energy that is emitted. While some devices have a fixed emissivity, others can have an adjustable one. To decide which one is best for you, keep in mind your intended application.
Distance-to-spot Ratio/Field of View
If your application requires you to have to stand at a distance from the object being measured, then you should consider buying a device which has the appropriate distance-to-spot ratio.
By keeping these factors in mind you will be able to purchase a digital infrared thermometer that can meet your application specific requirements.