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specifications
A precise statement of the set of requirements satisfied by a measurement system or
device.
stability
A measure of the freedom from drift in value over time and over changes in other
variables such as temperature. Note that stability is not the same as uncertainty.
standard
A device that is used as an exact value for reference and comparison.
standard cell
A primary cell that serves as a standard of voltage. The term "standard cell" often refers
to a "Weston normal cell," which is a wet cell with a mercury anode, a cadmium mercury
amalgam cathode, and a cadmium sulfate solution as the electrolyte.
systematic errors
Errors in repeated measurement results that remain constant or vary in a predictable way.
temperature coefficient
A factor per °C deviation from a nominal value or range that the uncertainty of an
instrument increases. This specification is necessary to account for the thermal
coefficients in a calibrator's analog circuitry.
test uncertainty ratio
The numerical ratio of the uncertainty of the measurement system or device being
calibrated to the uncertainty of the measurement system or device used as the calibrator.
(Also called "test accuracy ratio.")
thermal emf
The voltage generated when two dissimilar metals joined together are heated.
thermocouple
Two dissimilar metals that, when welded together, develop a small voltage dependent on
the relative temperature between the hotter and colder junction.
traceability
The ability to relate individual measurement results to national standards or nationally
accepted measurement systems through an unbroken chain of comparisons, i.e., a
calibration "audit trail."
Measurements, measurement systems or devices have traceability to the designated
standards if and only if scientifically rigorous evidence is produced in a continuing basis
to show that the measurement process is producing measurement results for which the
total measurement uncertainty relative to national or other designated standards is
qualified.
transfer error
The sum of all new errors induced during the process of comparing one quantity against
another.
transfer standard
Any working standard used to compare a measurement process, system, or device at one
location or level with another measurement process, system, or device at another location
or level.
transport standard
A transfer standard that is rugged enough to allow shipment by common carrier to
another location.
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Glossary
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