The Mikron M305 blackbody calibration source works between 100 and 1000℃ and has an emissivity of 0.995. It is used to calibrate the electrical response of the photodetectors developed in our laboratory when their spectral irradiance distribution follows the Planck´s law. This measure of absolute responsiveness (with black body) can be performed in an optical cryostat between 12 and 300 K, using quartz (SiO₂), ZnSe or Ge windows that are respectively totally transparent in the visible, partially transparent or totally opaque.