Traceability in measurement or measurement traceability is the condition where no links are missing to the real agreed reference standard.
The real agreed reference standard means a particular reference that the nations over the world agree to establish it as standard. For example, the nations over the world establish the path traveled by light in a vacuum in 1/299 792 458 of a second as the reference of 1 meter.
By having this uniformity, there will be no difference between the version of one meter in country A and the rest countries. The mess has been overcome.
Traceability and Accuracy
Traceability and accuracy cannot be separated. To be stated as accurate, the one meter of a particular measurement must be one meter of the agreed value (one meter of the International Reference Standard light travel above).
However, the issue is how can you tell that one meter of the measurement you gain matches with the international reference standard? In other words with a sample, how can you tell that one inch of your micrometer measures is one inch of the international reference standard?
You must be referring to the gauge blocks. It’s the most portable calibration set you can rely on.
But how is the manufacturer of the gauge block sure that one inch of the gauge block is one inch of the international reference standard?
They must match it to the other standard which has better accuracy. It seems that there is another standard reference owned by the company. In this case, Mitutoyo produces gauge blocks. They have their own lab that has a standard reference.
But how can you tell that one inch of the standard reference of Mitutoyo Lab matches one inch of the international reference standard?
They can match it to the broader authority with better accuracy such as a national standard. In this case, the national standard in the United States is NIST (National Institute of Standards and Technology).
And finally, the one inch of the NIST lab must match to the international reference standard.
From the paths above, as the end users, we realize that the most reachable standard reference is gauge block. Even though we could go to the NIST lab directly, the process could take too long.
Simply, we can shape the link like the following:
International Standard Reference (SI) >> National Standard Reference (NIST) >> Mitutoyo America Calibration Lab Masters (Company Lab) >> End Users (Human)
The link might be longer than the link above. It depends on the institutes that involve. The shorter the links, the better due to lower uncertainty.
No matter how short or far the links, as long as it’s traceable to the International Standard Reference (SI / Standard International) that takes place as the world’s agreed standard, the measurement is trustable.
Traceable measurement is extremely important to gain an accurate measurement for sure. This is to assure the credibility of the measurement for the users. If one of the link chains is broken, the measurement is simply questionable.