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accuracy
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The difference between a measurement reading and the true value of that measurement.
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anvil
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The fixed, nonadjustable block on a micrometer. The face of the anvil is used as the reference from which the dimension is taken.
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auditor
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An individual outside of an organization who objectively evaluates the effectiveness of a company's quality system.
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calibration
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The comparison of a device with unknown accuracy to a device with a known, accurate standard to eliminate any variation in the device being checked.
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calibration laboratory
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A controlled test environment where higher-level calibration is performed. These calibration results should be traced back to NIST.
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calibration record
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A document displayed with a measuring instrument that contains information about its calibration. Calibration records help maintain accuracy and traceability.
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calibration report
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A document that contains information about a particular calibration procedure. Calibration reports maintain traceability.
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correction factor
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The amount of deviation in a measurement that is accounted for in the calibration process. The correction factor can be added to the measured value, or the measuring instrument can be adjusted.
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dial indicator
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A measuring instrument with a contact point attached to a spindle and gears that move a pointer on the dial. Dial indicators have graduations that are available for reading different measurement values.
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drift
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The actual change in the measurement value when the same characteristic is measured under the same conditions, with the same operator, at different points in time. Drift indicates how often a measurement needs recalibration.
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error
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The amount of deviation from a standard or specification. Errors should be eliminated in the measuring process.
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gage block
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A hardened steel block that is manufactured with highly accurate dimensions. Gage blocks are available in a set of standardized lengths.
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hierarchy
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A group of items classified lowest to highest according to ability. The hierarchy of measurement standards is classified according to quality.
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international standard
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A measurement standard recognized by international agreement and used as the basis for assigning values to other standards.
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ISO 9000
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A collection of documents that lists requirements for the creation and implementation of an effective quality system.
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ISO 9001:2000
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The section of the ISO 9000 standard containing the list of requirements. ISO 9001:2000 is the auditable section of the standard.
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light wave
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The pulsation in space that transmits light energy. Light wave values are used to determine primary standards.
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machine tool
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A power-driven piece of metalworking equipment for cutting or forming metal.
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master thread gage
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A gage that is used to calibrate thread ring gages. The master thread gage inspects the internal threads of the ring gages.
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measurement standard
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A recognized true value. Calibration must compare measurement values to a known standard.
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metrologist
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A scientist of measurement. Metrologists test the highest-quality standards.
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micrometer
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A hand-held measuring device used to inspect the dimensions of parts. The typical micrometer is accurate within 0.001 in. or 0.02 mm.
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National Institute of Standards and Technology
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An organization required by law to maintain national standards. This organization is formerly known as the National Bureau of Standards.
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precision
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The ability of a process to repeat the same accurate measurement over time.
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primary standard
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A measurement standard with the highest quality. A light wave is used to determine a primary standard.
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quality system
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The objectives and processes of a company designed to focus on quality and customer satisfaction.
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random error
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An error that results from unpredictable variations from one or more influenced quantities. Random errors are inconsistent and easily recognizable.
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secondary standard
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A measurement standard that is used in comparison with a primary standard. They are also known as transfer standards.
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spindle
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A rotating component on a micrometer that advances toward the anvil to make contact with the part.
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systematic error
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An error that is not determined by chance but is introduced by an inaccuracy in the system. Systematic errors are predictable and expected.
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time meter
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A device used with a measuring instrument that records the number of hours an instrument operates. Time meters help determine calibration cycles.
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tolerance
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An unwanted but acceptable variation from a specified dimension.
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traceability
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The ability to verify each higher step of calibration until the NIST international standards are reached.
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transfer standard
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A measurement standard that is used in comparison with a primary standard. They are also known as secondary standards.
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true value
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A measurement value with no errors. The true value can never be known with total certainty.
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uncertainty
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The measurement range in which the true value of a measurement is expected to lie. Uncertainty is an estimation of error.
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variation
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A difference between two or more similar things.
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working gage block
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A type of gage block that is used to calibrate measuring instruments. These are generally either Grade 2 or 3 gage blocks.
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working standard
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A measurement standard used to calibrate or check measuring instruments. Gage blocks are common working standards.
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wringing
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Bringing two surfaces of microinch flatness together so that they adhere, leaving only microinch separation. Gage blocks are wrung together in various combinations to form any length.
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