Editing Calibration (section)

==Instrument calibration prompts==
Calibration may be required for the following reasons:
* a new instrument
* after an instrument has been repaired or modified
* moving from one location to another location
* when a specified time period has elapsed
* when a specified usage (operating hours) has elapsed
* before and/or after a critical measurement
* after an event, for example
** after an instrument has been exposed to a shock, [[vibration]], or physical damage, which might potentially have compromised the integrity of its calibration
** sudden changes in weather
* whenever observations appear questionable or instrument indications do not match the output of surrogate instruments
* as specified by a requirement, e.g., customer specification, instrument manufacturer recommendation.

In general 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 [[Operational definition#Temperature|calibration]] constants) so that it shows the true temperature in [[Celsius]] at specific points on the scale. This is the perception of the instrument's end-user. However, very few instruments can be adjusted to exactly match the standards they are compared to. For the vast majority of calibrations, the calibration process is actually the comparison of an unknown to a known and recording the results.