Measuring instruments for pressure and temperature are employed in almost all areas of industrial manufacturing. Passionate to continuous mechanical, chemical and thermal loading, these instruments age and will therefore not guarantee the correctness of the measured values over the course of time. Through timely calibration, however, the alteration of the measured value could be determined.
In the process of calibration, the displayed value of the measuring instrument is compared with the measuring result of a different measuring device that 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 via a chain of comparative measurements. The calibration hierarchy shown in the picture (utilizing the example of Germany) depicts the traceability of an inspection equipment in an organization up to national standard at the PTB (German national metrology institute).
To be able to ensure traceability used, the following points must be observed, amongst others:
The chain of comparison should not be interrupted.
The measurement uncertainty must be known in each stage of the calibration chain so that the total measurement uncertainty can be calculated. As a rule, a superordinate measuring instrument must have a measurement accuracy 3 to 4 times higher.
Each part of the calibration chain must be documented, like the measurement results.
Maul conducting 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) in accordance with DIN EN ISO / IEC 17025 for the measurands temperature, pressure, DC current, DC voltage and DC resistance. More info on our calibration laboratory or an on-site calibration with the WIKA calibration van can be found on the WIKA website. If you are interested in our services, please feel free to e mail us via e-mail.
Find out more about the differences between factory calibration and traceable calibration in the following video: