The calibration process involves statutory testing of a measuring device while observing the requirements of the German Weights and Measures Act. This applies in particular to calibration error limits.
    An official seal confirms anticipated compliance for the period of validity.

    Calibration work is undertaken by the federal states’ weights and measures offices and state-recognised test bodies under the supervision of the Physikalisch-Technische Bundesanstalt. Calibration is therefore statutory and can be traced back to European standards.

    Only measuring devices of a type previously approved by the weights and measures office can be calibrated and legal-for-trade. An approval process, requested by the manufacturer of the measuring device, with e.g. the Physikalisch-Technische Bundesanstalt (PTB), is therefore required before calibration. The type approval involves checking whether the design and condition match the relevant calibration requirements. This is done in advance using technical documents. The devices must correspond to their accuracy class and their measurement stability must be ensured.

    EU validity: The type approval is documented by the EC type approval certificate. This type approval is valid in all member states of the European Union (EU). After approval, an approval mark is issued which must be clearly affixed to all measuring devices of this type.