Editing Calibration (section)

===Process description and documentation===
All of the information above is collected in a calibration procedure, which is a specific [[test method]]. These procedures capture all of the steps needed to perform a successful calibration. The manufacturer may provide one or the organization may prepare one that also captures all of the organization's other requirements. There are clearinghouses for calibration procedures such as the Government-Industry Data Exchange Program (GIDEP) in the United States.

This exact process is repeated for each of the standards used until transfer standards, [[certified reference materials]] and/or natural physical constants, the measurement standards with the least uncertainty in the laboratory, are reached. This establishes the [[traceability]] of the calibration.

See [[Metrology]] for other factors that are considered during calibration process development.

After all of this, individual instruments of the specific type discussed above can finally be calibrated. The process generally begins with a basic damage check. Some organizations such as nuclear power plants collect "as-found" calibration data before any [[Planned maintenance|routine maintenance]] is performed. After routine maintenance and deficiencies detected during calibration are addressed, an "as-left" calibration is performed.

More commonly, a calibration technician is entrusted with the entire process and signs the calibration certificate, which documents the completion of a successful calibration.
The basic process outlined above is a difficult and expensive challenge. The cost for ordinary equipment support is generally about 10% of the original purchase price on a yearly basis, as a commonly accepted [[rule-of-thumb]]. Exotic devices such as [[scanning electron microscope]]s, [[gas chromatograph]] systems and [[laser]] [[interferometer]] devices can be even more costly to maintain.

The 'single measurement' device used in the basic calibration process description above does exist. But, depending on the organization, the majority of the devices that need calibration can have several ranges and many functionalities in a single instrument. A good example is a common modern [[oscilloscope]]. There easily could be 200,000 combinations of settings to completely calibrate and limitations on how much of an all-inclusive calibration can be automated.

[[Image:F18NARack.JPG|thumb|An instrument rack with tamper-indicating seals]]

To prevent unauthorized access to an instrument tamper-proof seals are usually applied after calibration. The picture of the oscilloscope rack shows these, and prove that the instrument has not been removed since it was last calibrated as they will possible unauthorized to the adjusting elements of the instrument. There also are labels showing the date of the last calibration and when the calibration interval dictates when the next one is needed. Some organizations also assign unique identification to each instrument to standardize the record keeping and keep track of accessories that are integral to a specific calibration condition.

When the instruments being calibrated are integrated with computers, the integrated computer programs and any calibration corrections are also under control.