In the last few years, the sensitivity of Forward looking infrared (FLIR) devices has increased considerably. The requirements on the testing stations in production and in the field have changed accordingly. The heart of the test station is the infrared source, usually a "differential blackbody". In order to make much more accurate measurements, the source must be such that:
1. Its temperature and emissivity profiles are as uniform as possible.
2. The differential temperature is as stable as possible in the short term (hours) and long term (months).
3. The recalibration procedures are as simple as possible, reliable and traceable to an international standard.
4. The differential temperature is measured and displayed with high resolution (of the order of 0.001C).
CI has recently developed a new differential blackbody source, based on very stable electronics, and microprocessor based technology, in an effort to meet the modern requirements for this type of instrumentation. The microprocessor is especially useful to automatically take into account systematic temperature gradients between the probe used to control the temperature and the emitter surface, or the emissivity differences between the emitter and reference plate, if needed. CI has also developed new radiometric calibration and uniformity test techniques, which use a particular version of its telescopic radiometers. These radiometers can measure temperature differences of the order of millidegrees near room temperature, and are also based on a special microprocessor programme which translates the detector signal to a temperature reading. This paper will describe some of the common problems encountered in the differential blackbodies, and to some extent, the work recently performed at CI to solve them. A radiometric technique to measure the temperature uniformity and stability will also be described.