Objects having temperatures above absolute zero, radiate infrared energy. This energy travels in all directions, at the speed of light. When pointed at a target, the infrared thermometers' lens collects and focuses the energy onto a sensor. The detector responds by producing a voltage signal which is directly proportional to the amount of energy received, and therefore to the temperature of the target. By sampling and manipulating the output of the detector the units' microprocessor-based electronics can display the temperature, and related computed values such as maximum, minimum, average, and difference of temperature seen during the measurement.
Some objects reflect, as well as emit, infrared energy.
Shiny or highly polished surfaces tend to reflect energy, whereas dull ones do not. A factor called emissivity, which can have a value anywhere from 0.1 to 1.0, accounts for the actual energy being emitted. It may be adjusted using the front arrows on the Laser touch-sensitive membrane switch. Precious metals are the best heat conductors when located in the earth. The rising heat wave increases in size in proportion to the size of the target.