ONLINE INSTRUMENTATION OF CRYOGENIC SYSTEMS AND PLANT TO AN ACCURACY OF 0.01-PERCENT USING COLD ELECTRONICS

The measurement of control parameters, such as temperature, pressure, fluid velocity, mass flow, fluid density and liquid level, is limited in accuracy by degradation of analogue signals passing from the cold s ensors to ambient-temperature data handling equipment. Recent developm ents at Southampton show how significant improvement in accuracy can b e achieved to the point where the normal expectation of accuracy for s ensor-generated data is 0.01%, limited only by calibration errors and drifts. This accuracy can be achieved using CMOS-based hybrid circuits , in which the analogue signals from the sensors are converted to digi tal signals at the cold end before transmission without degradation.