Expected Accuracy when using Non-Calibrated CernoxTM Sensors

Within the ITER-CERN collaboration agreement, task “PROCUREMENT OF CRYOGENIC THERMOMETERS TO MONITOR ITER MAGNETS AND FEEDER TEMPERATURES”, CERN is investigating what would be the expected accuracy when using non-calibrated Cernox™ temperature sensors at 4.2 K. The cernox™ is a resistive type temperature sensor that is capable of measuring the full temperature range of interest for ITER, it is 4.2 K to 300 K. Non-calibrated cernox™ sensors are delivered with a table listing the resistance at the following temperatures: 4.2 K, 77 K and 300 K. CERN has deployed several thousands of individually calibrated cernox™ sensors and they are used to compare the manufacturer data at 4.2 K with their individual calibration performed by CERN. Within a sample size of 5’941 sensors, 99.39% of the population is able to provide a measurement within +/-0.1 K at 4.2 well within the requirements at low temperature specified by ITER.