Measuring instruments for pressure and temperature are employed in almost all areas of industrial manufacturing. Because 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 can be determined.
In the process of calibration, the displayed value of the measuring instrument is compared with the measuring consequence of another measuring device that 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. In short, to compare measuring results, they must be ?traceable? to Responsive 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 a national standard at the PTB (German national metrology institute).
As a way 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 three to four times higher.
Legitimate in the calibration chain must be documented, including the measurement results.
All bodies conducting a stage in the chain must prove their competence by means 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. Further information on our calibration laboratory or an on-site calibration with the WIKA calibration van are available on the WIKA website. For anyone who is interested in 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: