Measuring instruments for pressure and temperature are employed in almost all areas of industrial manufacturing. As a result of continuous mechanical, chemical and thermal loading, these instruments age and can therefore not guarantee the correctness of the measured values during the period of time. Through timely calibration, however, the alteration of the measured value could be determined.
In Selected of calibration, the displayed value of the measuring instrument is weighed against the measuring result of another measuring device which is recognized to function correctly and accurately and which itself has been made to coincide directly or indirectly with a national (or international) reference instrument. In a nutshell, in order to compare measuring results, they must be ?traceable? to a national or international standard with a chain of comparative measurements. The calibration hierarchy shown in the picture (utilizing the exemplory case of Germany) depicts the traceability of an inspection equipment in an organization up to national standard at the PTB (German national metrology institute).
So that you can ensure traceability in practice, the following points should be observed, among others:
The chain of comparison must not be interrupted.
The measurement uncertainty must be known in each stage of the calibration chain in order that the total measurement uncertainty can be calculated. Generally, a superordinate measuring instrument should have a measurement accuracy 3 to 4 times higher.
Each part of the calibration chain must be documented, including the measurement results.
All bodies carrying out a stage in the chain must prove their competence by way of accreditation.
Calibrations must be repeated at appropriate intervals. The periods depend on the demanded measurement accuracy and the technical requirements
Note
The WIKA calibration laboratory is accredited by the German Accreditation Body (Deutsche Akkreditierungsstelle ? DAkkS) relative to DIN EN ISO / IEC 17025 for the measurands temperature, pressure, DC current, DC voltage and DC resistance. Eliminate on our calibration laboratory or an on-site calibration with the WIKA calibration van are available on the WIKA website. For anyone who is thinking about our services, please feel free to e mail us via e-mail.
Know more about the differences between factory calibration and traceable calibration in the following video: