Measuring instruments for pressure and temperature are used in almost all areas 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 during the period 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 weighed against 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 a nutshell, 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 (using the example of Germany) depicts the traceability of an inspection equipment in a company up to a 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 must not be interrupted.
The measurement uncertainty should be known in each stage of the calibration chain so the total measurement uncertainty can be calculated. Generally, a superordinate measuring instrument should have a measurement accuracy three to four times higher.
Each part of 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 should be repeated at appropriate intervals. Frenzied 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 are available on the WIKA website. If you are interested in our services, please feel absolve to contact us via e-mail.
Find out about the differences between factory calibration and traceable calibration in the following video: