Calibration

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Calibration refers to the process of determining the relation between the output (or response) of a measuring instrument and the value of the input quantity or attribute, a measurement standard. In non-specialized use, calibration is often regarded as including the process of adjusting the output or indication on a measurement instrument to agree with value of the applied standard, within a specified accuracy. For example, a thermometer could be calibrated so the error of indication or the correction is determined, and adjusted (e.g. via calibration constants) so that it shows the true temperature in Celsius at specific points on the scale. Calibration also can refer to judgments made by a prognosticator, for example, a weather-forecaster who states that "there is an 80% chance of rain today," if properly calibrated, will say this on precisely 80% of the days during which it rains.

In the United States, the National Institute of Standards and Technology, a part of the federal government, maintains standards and is considered the arbiter and ultimate (in the U.S.) authority for values of SI units and industrial standards. NIST also provides traceability to its standards by calibration, by which an instrument's accuracy is established by comparing, in an unbroken chain, to higher level standards, e.g. the standards maintained by NIST. For each step in the process, the measurement uncertainty is evaluated.

In computing, an interactive whiteboard pen or other input method can be calibrated so that relation between the physical pen position and the position of the cursor on the screen is established and properly adjusted.