The traceability chain - the link to basic quantities A key concept of measurement technology is that of traceability, which means that all measurements made with a calibrated instrument or device must have a directly traceable link back to the defined quantity.
The first link in the traceability chain is RISE national standard
The direct relationship is provided by a traceability chain, each link of which is represented by a calibrated measurement standard. The first link in the chain must be a national standard, such as those held or maintained/provided by RISE. All users of traceably calibrated measuring devices or instruments can therefore be quite certain that they really are using the same unit. The chain can be extended to any number of links, although each additional link increases the uncertainty of measurement.
The traceability pyramid
The concept of traceability is therefore usually represented by a traceability pyramid. At the top of the pyramid is the definition of (say) the metre. Below it are all the links in the traceability chain, with the width of the pyramid therefore becoming broader as the uncertainty of measurement increased. A basic rule of thumb is that the fewer the links, the less the uncertainty of measurement.