The acquisition of thermal radiation for measuring the temperature of aluminium is one of the most difficult measuring tasks. On the one hand, aluminium is a very poor heat radiator. On the other hand, the surface properties and thus the emissivity of aluminium can vary greatly. Based on patented measurement value processing and constant light technology, KELLER ITS has developed a pyrometer that can reliably detect and evaluate even the smallest infrared radiation. For this purpose, the devices have a high-intensity lens, a highly sensitive photodiode, extremely low-noise signal processing and an adaptive software algorithm to compensate for the influence of ambient temperature.