About 25 years ago, I first visited the Instrumentation Labs at Oak Ridge National Laboratories (ONRL) at the invitation of the late Bob Shepard. Bob was a pioneer in many areas of temperature measurement and at that time was the Chairman of ASTM Committee E20 on Temperature. He was also head of the lab at ORNL.
He introduced me to Johnson Noise Temperature (JNT) measurement and showed me a prototype device that they had developed at Oak Ridge to implement the method as an possible alternate means to verify the calibration in situ of thermocouples in a nuclear reactor environment.
While the method was very complex, Bob was convinced it would eventually become commercially viable, if for no other reason than it was a fundamental technology related to the Absolute Thermodynamic Temperature Scale (Kelvin Scale) and required no calibration.
Work has continued to this day at ORNL and elsewhere. More recently, the staff at the National Institute of Standards & Technology (NIST) Thermometry Group have been producing some remarkable results, prototype devices and a raft of technical papers on the subject.
First a description about this unique temperature measurement method that has been studied for more than 30 years.
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