Measuring instruments for pressure and temperature are employed in almost all regions of industrial manufacturing. Because of 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 can be determined.
Along the way of calibration, the displayed value of the measuring instrument is compared with the measuring result 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 a nutshell, in order to compare measuring results, they must be ?traceable? to a national or international standard with a chain of comparative measurements. Dazzling shown in the picture (utilizing the exemplory case of Germany) depicts the traceability of an inspection equipment in a company up to national standard at the PTB (German national metrology institute).
As a way to ensure traceability in practice, the following points should be observed, amongst others:
The chain of comparison should not be interrupted.
The measurement uncertainty should 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.
Silly of the calibration chain must be documented, including the measurement results.
All bodies following a stage in the chain must prove their competence by way of accreditation.
Confessions should 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. Further information on our calibration laboratory or an on-site calibration with the WIKA calibration van are available on the WIKA website. In case you are interested in our services, please feel absolve to e mail us via e-mail.
Read more about the differences between factory calibration and traceable calibration in the following video: