INTRINSIC (?) REFERENCE STANDARDS

摘要

The term "intrinsic" refers to something that is inherent in the nature of a thing. In metrology, it usually concerns a characteristic property of a material or process. Many international standard scales are now based on intrinsic natural properties rather than on physical artifacts. Such scales include those for time, dimension, temperature, voltage, and resistance. Ideal intrinsic references are reproducible and independent of place, time, or observer. Ideal intrinsic references do not require calibration. They represent quantities and values that are exact by definition. Such references might be exempt from calibration traceability to a national laboratory. Distinguish, however, between the intrinsic properties on which measurement scales are based and physical realizations of particular values of those properties in actual devices for calibration. It must not be casually assumed that a physical reference standard that employs a class of natural phenomenon does, necessarily, impose the standardized value on a calibration subject. Some authentication of real references is appropriate. Some of the problems of practical use of so-called intrinsic references in applied measurement practice will be considered. In particular, I discuss distinctions between validation, qualification, and calibration of intrinsic reference standards and implications for measurement quality assurance. Examples are taken from low, medium, and high temperature intrinsic references.