Traceability Chain

The traceability chain is the documented sequence of calibration comparisons that links a measurement result back to national standards. Starting with NIST primary standards, each successive calibration comparison creates a link. When DMS uses their NIST-certified reference transducer to calibrate a customer's dynamometer, that instrument has a documented, multi-link chain back to the national standard.

There is no prescribed maximum, but each additional link adds measurement uncertainty. Most commercial calibration chains have two to four links between the customer's instrument and the NIST primary standard. Audit standards require that the chain be complete and documented — each link traceable to the next — regardless of the number of steps.

Look for the reference standard identification on the certificate — a certified reference standard will have its own certificate number from an accredited laboratory. That certificate documents the next link up the chain. If the calibration provider cannot produce documentation of their reference standards' own traceability, the chain is broken and the calibration is not genuinely NIST-traceable.