Calibration terminology
Accuracy
Closeness of the agreement between the result of a
measurement and a true value of the measurand.
- Accuracy
is a qualitative concept.
- The
term precision should not be used for accuracy.
Adjustment (of a measuring instrument)
Operation of bringing a measuring
instrument into a state of performance suitable for its use.
Please note:
- Adjustment
of measurement instrument is usually made at one or two points and not
even on every range of a multirange instrument.
- After
adjustment the reading of the instrument is not automatically correct but
there will be remaining error which may be significant depending on the
use of the instrument.
- After
adjustment the instrument should fulfill the instrument specifications.
Calibration
Set of operations that establish, under specific conditions,
the relationship between values of quantities indicated by a measuring
instrument or measuring system, or values represented by a material measure or
a reference material, and the corresponding values realized by standards.
- The
result of a calibration permits either the assignment of values of
measurands to the indications or the determination of corrections with
respect to indications.
- A
calibration may also determine other metrological properties such as the
effect of influence quantities.
- The
result of a calibration may be recorded in a document, sometimes called a
calibration certificate or a calibration report.
Repeatability (of results of measurements)
Closeness of the agreement between the results of successive
measurements of the same measurand carried out under the same conditions of
measurement.
- These
conditions are called repeatability conditions which include:
- the
same measurement procedure
- the
same observer
- the
same measuring instrument, used under the same conditions
- the
same location
- repetition
over a short period of time
- Repeatability
may be expressed quantitatively in terms of the dispersion characteristics
of the results.
Reproducibility (of results of measurements)
Closeness of the agreement
between the results of the same measurand carried out under changed conditions
of measurement.
A valid statement of reproducibility requires specification of the conditions
changed which may include:
- principle
of measurement
- method
of measurement
- observer
- measuring
instrument
- reference
standard
- location
- conditions
of use
- time
- Reproducibility
may be expressed quantitatively in terms of the dispersion characteristics
of the results.
- Results
are here usually understood to be corrected results.
Uncertainty of measurement
Parameter, associated with the result of a measurement, that
characterizes the dispersion of the values that could reasonably be attributed
to the measurand
- The
parameter may be, for example, a standard deviation (or a given multiple
of it), or the half-width of an interval having a stated level of
confidence.
- Uncertainty
of measurement comprises, in general, many components. Some of these
components may be evaluated from the statistical distribution of the
results of series of measurements and can be characterized by experimental
standard deviations. The other components, which can also be characterized
by standard deviations, are evaluated from assumed probability
distributions based on experience or other information.
- It
is understood that the result of the measurement is the best estimate of
the value of the measurand, and that all components of uncertainty,
including those arising from systematic effects, such as components
associated with corrections and reference standards, contribute to the
dispersion.
Traceability (of a measurement)
Property of the result of a measurement or the value of a
standard whereby it can be related to stated references, usually national or
international standards, through an unbroken chain of comparisons all having
stated uncertainties.
- The
concept is often expressed by the adjective traceable.
- The
unbroken chain of comparisons is called a traceability chain.