Abstract: An IR temperature sensor comprises a sealed housing containing an inert gas atmosphere and enclosing a detector for conversion of heat radiation into an electrical signal, an optical system which images the heat radiation emanating from an object onto the detector, a heat-conducting temperature equalization element which maintains the detector and the optical system at a common temperature, and a temperature sensor which measures the temperature of the temperature equalization element. The sealed housing protects the sensor from the external environment and maintains uniform temperature between the optical system and the sensor.

Abstract: A pyrometer for measuring the electromagnetic radiation emitted by an object comprises a first detector to which the radiation is delivered through an optical system as well as a second detector to which the radiation emanating from a reference element is delivered through the same optical system. The temperature of the reference element is monitored and a rotary optical modulator periodically enables and disables the delivery of radiation to the detectors. The output signals from the two detectors are processed to determine the difference therebetween. The sensed temperature of the reference element is taken into account as a part of determining the difference between the two detector output signals. In this way it is possible for the characteristic radiation of the optical system largely to be suppressed. The optical modulator comprises a semi-circular disk having a polyethylene terephthalate substrate coated on each side with metal. The disk is rotated through 180.degree.