An Investigation of Long-Term Stability of a Precision Platinum Resistance Thermometer up to 660°C

Document(s): 

An Investigation of Long-Term Stability of a Precision Platinum Resistance Thermometer up to 660°C (116.39 KB)

A new precision (secondary) platinum resistance thermometer with an upper temperature limit of 661°C and an inconel protection sheath was developed at Hart Scientific five years ago. In order to verify the long-term stability of these thermometers at high temperatures, a few were tested for stability at 665°C over 20,000 hours. The drifts of the thermometers’ resistance at the triple point of water were as good as the equivalent of 0.002°C after the thermometers were exposed to 665°C for over 1000 hours. After long-term exposure to high temperature, the thermometers were calibrated to determine whether they still met the requirements of ITS-90. In this paper, the test results of some of these thermometers are presented. Some issues that may affect the stabilities of the thermometers are discussed. And the stabilities of some customers’ thermometers returned for routine calibrations are also reported.