A New Capsule Platinum Resistance Thermometer for Cryogenic Use

Standards grade platinum resistance thermometers (SPRTs) obtain their high stability in part due to the strain-free mounting of the sensing wire. The space required for this strain-free mounting normally results in thermometers on the order of 6 mm diameter by 40 mm length in size. While these SPRTs are acceptable in many applications, it is desirable to reduce the size as much as possible for cryogenic use where space is of major concern. For over 40 years Minco Products, Inc. provided a smaller alternative with their model S1059, a high-stability cryogenic capsule platinum resistance thermometer (PRT) packaged in a copper canister sized only 3.2 mm diameter by 9.7 mm length. The packaging was compatible for use over the 13 K to 533 K temperature range. Unfortunately, this product was discontinued in 2009. In its absence, Lake Shore Cryotronics, Inc., has worked with Advanced Sensing Products to develop a similarly sized replacement sensor for cryogenic use. The replacement capsule PRT is manufactured using the model S1059 design, but with modifications to reduce the chance of lead breakage at the epoxy-lead interface. Test devices have been fabricated and tested for temperature response and stability upon repeated calibration from 13 K to 330 K. The new sensor design features and performance data are presented in this work.