New Technologies for Noise Thermometry with Applications inHarsh and-or Remote Operating Environments

摘要

Johnson noise thermometry (JNT) utilizes the fundamental properties of thermal fluctuations inconductors to measure thermodynamic temperatures. Because the technique is a primary method, asopposed to a secondary or artifact method, the sensor response does not require calibration. Aninnovative JNT method now being developed at NIST links the measured thermal voltage directly tothe as-maintained electrical units via an AC Josephson Voltage Standard. A pulse-driven array ofJosephson Junctions serves as a Quantized Voltage Noise Source (QVNS) using digital synthesis togenerate pseudo noise. The QVNS output noise can be precisely matched in noise power to that of theJohnson noise in a resistance temperature probe without the use of attenuators. The new NISTmethodology conveys key advantages from a primary metrology standpoint and can also extend thepractical application range for JNT systems. These advantages make it well suited to the mostdemanding process measurement applications such as in high-temperature, high-radiation, or remoteenvironments where artifact thermometer servicing requirements can compromise the process or addexcessive costs.