Measurement traceability is one important factor for laboratories as it complies with ISO17025 accreditation. Measurement traceability can be simply described as a method of ensuring that measurements are taking into consideration all uncertainties and is representative of the most accurate measurement captured. Measurement should be tested against larger calibration reference standards and should be referenced to an unbroken chain of calibration documents, each presenting uncertainty measurement.
Why is Measurement Traceability Important?
Why is measurement traceability important? Well, it provides confidence and assurance that a taken measurement value meets national and international standards. It allows independent verification of an accreditation, reducing the risk of false information. Bear in mind that any activity performed within an organization can affect health and safety to a customer. If you think about it, measurements are used everywhere and everyday, whether it is for medical equipment purposes, to manufacture products, perform tests, the list is endless. The work performed in-laboratory has a significant impact on the society and organizations must be vigilant and ensure that procedures and programs are in place and can provide accurate calibration tests report.
When performing test and calibration reports, it can directly affect metrological traceability. The uncertainty estimated in reports are traceable uncertainty. This unit is then used in uncertainty budgets to evaluate the Calibration and Measurement Capability (CMC) or (TUR) Test Uncertainty Ratios. Usually, the smaller the chain between the laboratory to a national metrology institute, the smaller the uncertainty in measurement will be seen, increasing the confidence and assurance of every measurement taken.
To better visualize the chain, see below image of a Measurement Traceability Pyramid:
This graph demonstrates measurement traceability and the calibration hierarchy from the realization of SI Units to the measurements performed of Process Instruments.
For example, if you are sending your temperature sensors or thermometer directly to NIST (National Institute of Standards and Technology) for calibration, you should expect to see less uncertainty in measurement than if you were to send it to an accredited calibration laboratory. The closer to the SI Units, the less uncertainty measurement should be seen, the more accurate your equipment or instrument measurement will be.
Traceability Requirements of ISO17025
Quality system should meet the requirements of international standards if a laboratory is seeking ISO17025 accreditation.
Here’s a list of requirements of the ISO17025 standard and policy on traceability:
Calibrate internal equipment if they have a significant effect on measurement accuracy or validity
Having procedures and programs implemented for calibrating an equipment
Programs should include controlling and maintaining measurement standards, reference materials and measuring test equipment.
Programs for calibration should operate to ensure that calibrations and measurements are traceable to the International System of Units (SI)
Measurement traceability means an unbroken chain of calibrations (Linking measurement standards to primary standards of SI Units of measure)
Laboratories can demonstrate competence, measurement capability and traceability in order to provide external calibration services.
Calibration Certificates issued by laboratories should assess measurement results, uncertainty ratios and state of compliance.
Laboratories should have programs and procedures for the calibration of its reference standards.
As seen, having programs and procedures in place for ensuring that measurement traceability policies are followed is essential. In order to do so, one organization must do its study and investigation to search for an ISO17025 accredited laboratory, verify it’s scope of accreditation and review calibration reports details issued from the institute.
Measurement Traceability is an important requirement of ISO17025 accreditation, as it affects the confidence in a measurement taken. Consequently, it is important to review the past history of an equipment, including calibrations results and frequency of maintenance. Establishing that an equipment or instrument accuracy is to a higher standard gives credibility for manufacturers, increasing the trust between the fabricant and the consumer.