Measure the radiation left by the warm surface of a human hand pressed on a wooden desktop! This radiometer is sensitive! It will measure the energy in a beam of radiation and is calibrated in Watts per meter. The detector is a thermopile consisting of a series of tiny thermocouples wired in series. The detector has a flat spectral response from .3 µm in the ultraviolet range to 15 µm wavelength in the infrared range. The detector area of about 2 mm2 is small enough to measure the energy in a laser beam. For broad sources of radiation, the instrument is sensitive through a 60º cone angle.