Calibration is the metrological test with which calibratable measuring instruments are checked, calibrated and certified. During calibration, the metrological properties of the measuring instrument to be calibrated are compared with reference or measurement standards of the Physikalisch-Technische Bundesanstalt
(PTB). In addition to the Physikalisch-Technische Bundesanstalt, only verification offices and approved testing laboratories may perform verification. The latter two institutions are subject to the sovereignty of the Länder and are supervised by the Verification Supervisory Authority.characteristics and whether the measurement deviations comply with the permissible deviations of the calibration regulations. If the metrological requirements are met, this is documented with a calibration certificate.