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The formal definition of calibration by the International Bureau of Weights and Measures (BIPM) is the following: "Operation that, under specified conditions, in a first step, establishes a relation between the quantity values with measurement uncertainties provided by measurement standards and corresponding indications with associated measurement uncertainties (of the calibrated instrument or ...
Instruments should be calibrated against a standard instrument that is known to be accurate, and ideally the calibration should be repeated at intervals. The most rigorous standards are those maintained by a standards organization such as NIST in the United States , or the ISO in Europe.
Test equipment tends to drift out of calibration over time, and the specified accuracy cannot be relied upon indefinitely. For more expensive equipment, manufacturers and third parties provide calibration services so that older equipment may be recalibrated and recertified.
Testing is the use of specialized and calibrated instruments to measure temperatures, pressures, rotational speeds, electrical characteristics, velocities, and air and water quantities for an evaluation of equipment and system performance.
Secondary reference standards: Reference standards calibrated against and traceable to primary WHO materials and intended for use in routine tests; Reference reagent: a WHO reference standard, the activity of which is defined by WHO in terms of a unit; For chemical substances some pharmacopoeias [10] use the WHO terms [11]
Gauge blocks are calibrated to be accurate at 20 °C (68 °F) and should be kept at this temperature when taking measurements. This mitigates the effects of thermal expansion . The wear blocks, made of a harder substance like tungsten carbide , are included at each end of the stack, whenever possible, to protect the gauge blocks from being ...
A piece of calibrated equipment is required for radiation leakage testing. This is usually a hand-held device with a sensing antenna that can be scanned over the areas where the door meets the casing to find any radiation hot-spots whilst the unit is operating. As microwave ovens are not normally designed to be operated without a load this will ...
Although a given calibrated microphone will often have been calibrated by other (secondary) methods, all can be traced (through a process of dissemination) back to a microphone calibrated using the reciprocity method at a National Measurement Institute. Reciprocity calibration is a specialist process, and because it forms the basis of the ...