Abstract: A non-contact infrared temperature sensing system for determining temperature values for a series of targets all having a similar emissivity value, which calculates an emissivity value for the targets based on the sensed total heat radiated from one target, an inputted temperature value for that target, and a temperature value for extraneous radiation from that target. The system then computes, for each subsequent target whose heat radiation is detected, a temperature value for each said target dependent upon the emitted component of radiation, and independent of the extraneous component of radiation from that target.