Traceability of measurement
Traceability overview of measurements
In addition, the NIST Handbook 150 of the United States provides an additional description of the retrospective nature of measurement equipment as "its own measurement standards and measuring instruments to the SI by means of an unbroken chain of calibrations or comparisons linking them to relevant primary standards of the SI units of measurement."
Therefore, when it is intended to demonstrate traceability to be recognized by KOLAS, the laboratory shall ensure not only unbroken chain of calibrations or comparisons to national standards, but also such links are subject to the inherent uncertainty, assurance of the measurement process, continuous maintenance of standard and proper calibration procedure.
Why is traceability important in measurement?
Measurements are everywhere around us, but in spite of their importance they are often overlooked. Also, since tests are based on measurements, mutual accreditation of measurement and measurement traceability is the most essential precondition for mutual recognition of test results.
Nowadays, we are fully aware of the importance of quality in the international market and the need of quality systems such as ISO 9000. However, it is clear that the quality system itself is not guarantee for producing good quality. A quality system is a mechanism for overseeing processes and ensuring consistency, not quality assurance. In fact, a quality system can also be a means of continuously producing defective products if the measurement or measurement process involved in the manufacturing process or test is inaccurate.
In the case of raw material inspection, process control or finished product testing, the quality assurance requirements for measurement or measurement results are related to two aspects: competence and traceability of measurement. This capability relates to measurement personnel, measurement methods and quality systems, and is best demonstrated through third party recognition in accordance with ISO / IEC 17025. The traceability of the measurement is related to the accuracy of the measuring equipment. The indication of the measuring instrument or the result given by the instrument must be accurate in the physical unit in which the measurement is made and ultimately requires traceability to the measurement standard through calibration for the basic realization of the unit. The demand for international approvals for product testing and conformance in the global market is continuously increasing and requires traceability to international measurement standards.
Worldwide recognition of traceability
As the realization of the SI unit, the base standard is likely to be a very specific single-valued standard, and there is heightened international interest in the fact that proven traceability to these standards does not adequately demonstrate its capability in a wide range of quantities or values have. For this reason, the National Metrology Institute is under increasing pressure to participate in a broader range of international comparisons in order to demonstrate more thorough retrospective performance.
For example, proof of traceability through an international comparison of the 1 ohm base standard for the electrical resistance field does not prove the ability to measure very large resistance values that require slightly different techniques. This issue has been consistently addressed by the International Bureau of Weights and Measures and the International Bureau of Weights and Measures has prepared comparative programs in each of the metrology fields to broaden the credibility of the retrofit and the capabilities of the national metrology laboratories. This will form the basis of a global mutual recognition agreement.
"In conclusion, measurement is essential for building the foundation for testing, conformity assessment and international trade, which are essential elements of national economic development. In addition, the mutual recognition of national measurement standards and the capacity of national measurement laboratories is a prerequisite for maintaining the traceability of international measurement standards. "
Concept of Measurement Traceability
- National Measurement Standards
- Master Instrument
- Field Master
The measuring instrument must be calibrated with a high standard of accuracy.