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Chapter 12: F. Calibration 117
2. CALIBRATION STANDARDS
Describe the hierarchy of standards, from
working standards through international
standards. (Comprehension)
Body of Knowledge II.F.2
Calibration standards are known, highly accurate, and verifiable quantities used
as the basis of comparison in calibration processes. Virtually all industrialized
nations maintain a set of calibration standards for the measurement of various
quantities and phenomena.
The National Institute of Standards and Technology (NIST) is the custodian
of measurement standards in the United States. NIST was established by an act of
Congress in 1901, although the need for such a body had been noted by the authors
of the Constitution. NIST has two main facilities and laboratories in Gaithersburg,
Maryland, and Boulder, Colorado, where research into the phenomenon of
measurement, the properties of materials, and calibration of reference standards
is carried out.
There are several levels of calibration standards arranged in a hierarchy. At
the highest level in a calibration standard hierarchy are international standards,
which serve as the basis of trade between nations. At the lowest level in a calibration
standard hierarchy are transfer standards, which serve as the basis of trade
between organizations. Calibration standards at the lowest levels in the hierarchy
are used to support day-to-day operations by technicians and shop floor operators.
Calibration standards in the middle of the hierarchy are generally used by
personnel dedicated to calibration processes working in calibration laboratories.
Calibration standards at the highest levels in the hierarchy are generally used
by calibration specialists and government officials.
Figure 12.2 presents a hierarchy of calibration standards provided, with permission,
by Bucher (2004 and 2006).
• International standards. A standard recognized by international
agreement to serve internationally as the basis for fixing the value
of all other standards of the quantity concerned.
• National standards. A standard recognized by an official national
decision to serve in a country as a basis for fixing the value of all
other standards of the quantity concerned. Generally a national
standard in a country is also a primary standard to which
other standards are traceable.
• Primary standards. A standard that is designed to have or widely
acknowledged as having the highest metrological quality and whose
value is accepted without reference to other standards of the same
quantity. National standards are generally primary standards.
Part II.F.2