The accuracy of digital infrared thermometers is directly related to its distance-to-spot ratio. In this rule, there is a direct relationship between distance and the area being measured. The larger the area, the farther is the distance. Alternatively, the smaller the area being measured, the shorter is the distance between the thermometer and the object being measured. This plays well into the measuring range of digital infrared thermometers. For example, if an object has a size of 6 inches and the infrared thermometer has a DS ratio of 12:1, then you can actually position the thermometer some 72 inches or 6 feet away from the object and would still be guaranteed an accurate reading. If you move the thermometer a few inches farther, then you are not only measuring the 6-inch ‘spot’ but also its immediate surroundings. If this immediate surrounding is cooler than the ‘spot’ this will have an effect on the accuracy of the temperature reading. As such, if one is to understand the measuring range of IR thermometers, then one clearly has to understand the underlying principle of the distance-to-spot ratio.