The Cyclops Model 878 is a spherical black body source. It consists of an inner black sphere seated inside a spherical furnace, and is suitable for use as a radiation source for infrared thermometers.

The inner sphere has a nominal diameter of 230mm, and is accessed by an optical sightings tube. The black body furnace can be supplied in one of two constructions, one providing an aperture size of 17mm, and one of 45mm.

The emissivity of the material is 0.98. The outer case viewing hole has an aperture of 17mm as standard. An aperture of 50mm is available by special order, giving an apparent emissivity in relation to the wall greater than 0.999.

The infrared calibrator can be adapted for thermocouple operation by replacing the inner sphere with an equalizing black one and using a different control sensor.