Measuring instruments for pressure and temperature are used in almost all regions 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 over the course of time. Through timely calibration, however, the alteration of the measured value could be determined.
In No Strings Attached of calibration, the displayed value of the measuring instrument is compared with the measuring result of a different measuring device which 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 must be ?traceable? to a national 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).
To be able to ensure traceability in practice, the following points should 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 the total measurement uncertainty could be calculated. Generally, a superordinate measuring instrument must have a measurement accuracy three to four times higher.
Each step in the calibration chain should be documented, including the measurement results.
All bodies carrying out a stage in the chain must prove their competence through accreditation.
Calibrations 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 can be found on the WIKA website. For anyone who is thinking about 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 following video: