Robust instrumentation for high accuracy temperature measurement

A robust, highly stable, resistance thermometry instrument has been developed for use in the on-board calibration system of a space-borne infrared radiometer. At the beginning of its life, the reproducibility has been demonstrated to be better than 2.5 mK. The instrument uses an AC bridge based on novel miniature inductive components and nonelectromechanical inter-stage switching which results in a unit weighing /spl sim/1.5 kg. Several units of similar design have been built to withstand high levels of mechanical vibration and shock, extended temperature ranges, operation in vacuum and exposure to ionising radiation.