Measuring instruments for pressure and temperature are used in almost all regions of industrial manufacturing. Due to continuous mechanical, chemical and thermal loading, these instruments age and may 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 result of another 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 short, to be able to compare measuring results, they need to be ?traceable? to a national or international standard with 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 a company up to national standard at the PTB (German national metrology institute).
So that you can ensure traceability used, the following points should be observed, amongst 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. As a rule, a superordinate measuring instrument should have a measurement accuracy 3 to 4 times higher.
Discount in the calibration chain should be documented, including the measurement results.
All bodies following a stage in the chain must prove their competence through accreditation.
Calibrations must be repeated at appropriate intervals. The periods be determined by 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. If you are interested in our services, please feel absolve to e mail us via e-mail.
Find out more about the differences between factory calibration and traceable calibration in the next video: