Diode Temperature Sensor Curve Estimation and Interchangeability for Non-Standard Excitation Currents

Abstract

Diode temperature sensors’ wide temperature range and interchangeability to a standard curve has led to their widespread use in the cryogenic industry. The standard curve for a given model is generated from the calibration of hundreds of diodes from that specific model lot. This is an expensive process and is usually carried out for only one excitation current, typically 10 μA, chosen as a trade off between self‐heating at lower temperature and signal‐to‐noise ratio. There are many applications, however, where either the temperature range is limited or a higher signal‐to‐noise ratio is desired. It’s useful in these cases to use a larger excitation current. Given the non‐linear diode I‐V characteristics, the results for the diode response and interchangeability at the standard curve cannot be arbitrarily generalized to other excitation currents. This research examined eleven diode Lake Shore Cryotronics model DT‐670‐SD temperature sensors. Calibration data for these devices were taken at twenty temperatures ranging from 2 K to 325 K and at seven excitation currents ranging from 1 μA to 1 mA. These data were analyzed to determine the effect of excitation current on the interchangeability as a function of temperature. A method for estimating the standard curve at nonstandard excitation currents is presented.