The amount of infrared radiation emitted from an object depends on its temperature. The new Hanna HI 99551 and HI 99556 infrared thermometers employ this technology to measure surface temperature. Infrared measurements are extremely practical with a fast response time, typically around 1 second. Another main advantage is the non-intrusive nature of the measurement. This feature is particularly attractive in the food industry since it translates itself into substantial savings by leaving products intact, especially those sealed or pre-wrapped. In order to measure the temperature, simply point to the product or the spot and hold down the appropriate key. The measured value will be immediately displayed on the LCD. This type of non-intrusive measurement is also useful when the surface temperature is high, for difficult-to-reach places or due to hygiene requirements. The way the Hanna HI 99551 and HI 99556 are designed with the wrist-strap and HOLD feature makes measuring easy. These features coupled with their fast response time, makes these meters particularly attractive for food distribution, retailing and supermarkets. The operator responsible for checking the temperature can perform more measurements during the same time frame. Both HI 99551 and HI 99556 run on a common 9V battery with low battery warning. The optional Hanna rubber boots will make the meters truly shockproof. If in addition to surface measurement, you must check the core temperature too, then HI 99556 is the ideal solution for you. Simply attach an optional external probe to the meter and you will have a 2-in-1 infrared-thermistor thermometer. If you require your meter to measure in Fahrenheit, simply replace " -00 " with " -01 " at the end of the part number.