Traceability
Traceability is a method of ensuring that measurements are accurate representations of the thing being measured by comparison back to a known reference.
It is possible to establish a chain of calibrations that ends at a national standards body such as NPL. This demonstrable linkage to national standards with known accuracy is called traceability. However measurements are only traceable if the calibration corrections and uncertainties are actually applied at every step in the chain back to the reference.
Be aware that in a successive chain of calibrations the uncertainty increases at every step of the chain.
Any organisation can achieve traceability to national standards and the SI through the correct use of a traceably calibrated instrument.
In many countries a National Metrology Institute (NMI) will exist which will maintain primary standards of measurement (the main SI units plus a number of derived units) which will be used to provide traceability for a customer’s instruments by calibration.
In the UK, the National Measurement System (NMS) is in place to enable measurements to be traceable back to national standards. As the UK’s National Measurement Institute, NPL is at the pinnacle of this system as the focus for physical measurements throughout the nation and for customers from abroad.
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