Infrared radiation (IR) thermometers measure temperature without contact. The object being measured essentially broadcasts information about its temperature constantly. The physics behind the broadcasting is known as Planck's Law of Thermal Radiation. The IR range falls between the visible portion of the spectrum and radio waves. IR wavelengths are usually expressed in microns, with the IR spectrum extending from 0.7 to 1000 microns. Only the 0.7-14 micron band is used for IR temperature measurement.