Stability of Cernox® temperature sensors stored at room temperature over a 29-year period

Abstract

Many cryogenic applications critically depend upon accurate temperature measurement for success. In certain applications, including aerospace missions, temperature sensor components are procured years in advance of the mission’s launch date in order to accommodate installation and ground-based testing. Once installed there is little opportunity for recalibration, so the stability of the sensor stored at room temperature over extended time periods becomes vitally important. One of the most common cryogenic temperature sensor types used in aerospace applications is the Cernox Resistance Temperature Sensor manufactured by Lake Shore Cryotronics, Inc., and has been commercially available since 1993. For 29 years a set of 35 sensors manufactured from two of the initial production wafers has been stored at room temperature in ambient atmosphere. These sensors have been periodically recalibrated over the 1.4 K to 325 K or 4 K to 325 K temperature range as appropriate to provide an estimate of the long-term stability of these sensors when stored at room temperature. Data for each temperature sensor were analyzed in terms of equivalent temperature shift between each subsequent calibration and its initial calibration in 1992. The data show that the overall 29-year average stability for devices from these two Cernox wafers roughly follows a stability of ±10 mK for temperatures below 10 K and 0.07% of temperature for temperatures above 10 K. Data for an additional nine Cernox devices from an actual JWST production build lot showed they all exhibited stabilities better than ±8 mK for T < 10 K and (ΔT/T) < ±0.075% for T > 10 K.