Net Zero Stocktake 2023

Introduction: Every measuring instrument is subject to ageing as a result of mechanical, chemical or thermal stress and thus delivers measured values that change over time. This cannot be prevented, but it can be detected in good time by calibration. The Egyptians already knew this almost 5000 years ago. The workers calibrated their yard sticks by comparing them with a “royal cubit” (approx. 52.36 cm) made of stone and thus managed to achieve, for example, side lengths on the Cheops pyramid of 230.33 m which differ from each other by only about 0.05 per cent. In the process of calibration, the displayed value of the measuring instrument is compared with the measuring result of a different measuring device which is known to function correctly and accurately and which itself has been made to coincide directly or indirectly with a national (or international) reference instrument (standard) (Fig. 1). One talks about verification  when the calibration has been carried out or supervised by an official body. Both of these variants are purely intended for determining the quality of the displayed values. No intervention to the measuring instrument itself is allowed. With adjustment, it is understood that there is an intervention to the measuring device in order to minimise a detected measuring deviation. Typically, adjustment is followed by a further calibration, in order to check and document the final state of the measuring instrument following the intervention. In contrast to verification, which will lose its validity after a period of time set by law, the validity period of a calibration is subject to practical specifications0.