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The system that establishes
the relationship between a measuring device
and a traceable reference standard. Calibration
may include detecting, correlating, reporting
or eliminating discrepancies in the accuracy
of the measuring instrument.
A standard of known accuracy. The standard
should be traceable to the national standard
of the country concerned. In the United
States that is the National Institute of
Standards and Technology (www.nist.gov).
Gage Repeatability and Reproducibility.
The combined effects of measuring systems
repeatability and reproducibility:
The change in bias over the
operating range of a measuring instrument.
See Measurement Systems Variation.
| Measurement
Systems Analysis |
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Measurement systems include variation and
error, just like any other process. When
a characteristic is measured the readings
that are recorded include this measurement
error.
It is easy to overlook this and assume
that measurements reflect the true value
of the characteristic. This can result in
fruitless attempts to improve the process
when the apparent variation is caused by
variations in the measuring system. Measurement
Systems Analysis should be an essential
precursor to introducing Statistical
Process Control, or using Design
of Experiments
The variation of the measurement system
is generally divided into repeatability
error and reproducibility error, hence Gage
R&R studies.
Errors that affect the accuracy of the
measurement include bias, linearity and
stability.
| Measurement
Systems Capability |
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Short term estimate of the Measurement
System Variation.
| Measurement
Systems Variation |
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See Gage R&R
See Measurement Systems Analysis
See Number of Distinct Categories
| Number
of Distinct Categories |
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A measure of the number of distinct (non-overlapping)
categories that can be distinguished by
a measuring system:
Used in attribute agreement
analysis. It is the percentage of the number
inspected where there is agreement. It can
be used to compare appraiser with each other,
appraisers with a standard or appraisers
with themselves on repeated inspections.
| Precision
to Tolerance Ratio |
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The ratio of the precision of the measuring
system to the allowed tolerance:
| Precision/Total
Variation Ratio |
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The ratio of the precision of the measuring
system to the total variation:
See Precision to Tolerance Ratio
See Precision/Total Variation Ratio
See Calibration Standard
In Measurement Systems Analysis, the variation
when one person measures the same item several
times, using the same measuring equipment.
In Measurement Systems Analysis, it is
usually taken to be the variation in the
average measurement that occurs when two
or more people measure the same items using
the same measuring technique. It may also
be used to compare different measuring devices
at different locations.
Smallest readable unit of a measuring instrument.
With measurement, the change in bias over
time. More generally the degree to which
the parameters of a process are stable over
time.
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