Calibration is the act of determining and documenting, in a traceable manner, the deviations between a measuring instrument called device under test (DUT) and a reference device called reference standard.
The result of this comparison shows the measuring deviations at different measurement points and can be provided in absolute or relative form. The regular calibration of measurement instruments ensures the precision and reproducibility of the measurement data. The reference measurement is made with a reference device.
Traceability refers to the uninterrupted chain of comparative measurements related to the measuring results of a measuring instrument and the specific, higher-ranking national standard.
The resulting hierarchy is based on accreditation, i.e. the calibrating authorities have been assessed for their technical competence and thus formally recognized. The Physikalisch-Technische Bundesanstalt (PTB) is the highest-ranking national authority for metrology, providing reference standards of the highest accuracy, such as the standard meter, for all physical and legally required quantities for use in calibration.
What is meant by "adjustment"?
As opposed to calibration, adjustment is the act of setting a measuring instrument to a measurement deviation that is reduced as much as possible in order for the deviations to stay within the limits of error. Thus, adjustment requires an intervention on the measuring instrument, which usually results in permanent changes to the device.
What is "Verification"?
Verification is about providing objective proof that a measuring instrument meets specific requirements.
As opposed to calibration, uncertainty of measurement is not indicated, only a pass or fail statement is made. Verification can cover secondary measurands such as the sensor, the transducer or I/O modules via test signals.
What is meant by "standardise"?
Standardisation means performing legally required checks of measuring instruments, e.g. scales used in food retailing, that are subject to public interest and are used to set prices. Standardisation is performed by specific authorities and is thus governed by severe regulations.