Measuring instruments for pressure and temperature are used in almost all areas of industrial manufacturing. As a result 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 Increase , however, the alteration of the measured value can be determined.
In the process of calibration, the displayed value of the measuring instrument is weighed against the measuring consequence of a different measuring device which is known to function correctly and accurately and which itself has been designed to coincide directly or indirectly with a national (or international) reference instrument. In short, 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 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 should be known in each stage of the calibration chain so that the total measurement uncertainty can be calculated. Generally, a superordinate measuring instrument should have a measurement accuracy 3 to 4 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 by means of 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) 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. Should you be interested in our services, please feel free to e mail us via e-mail.
Read more about the differences between factory calibration and traceable calibration in the next video: