Traceability belongs to the result
NIST’s policy adopts the metrology definition: a measurement result can be related to a reference through a documented unbroken chain of calibrations, each contributing to measurement uncertainty.
What to look for
| Evidence | Question to ask |
|---|---|
| Measured quantity | Is the certified value diameter, count concentration, another property or a combination? |
| Reference | What specified reference or higher-order standard anchors the chain? |
| Calibration method | How was the result obtained, and is the method appropriate for the size range? |
| Uncertainty | Is uncertainty stated and small enough for the intended decision? |
| Lot identity | Does the certificate identify the exact lot or unit being used? |
| Validity conditions | What storage, preparation and use conditions preserve the claim? |
The chain does not end at the bottle
Purchasing a reference material does not automatically make every result generated with it traceable. The user must control the measurement system, preparation, handling, instrument status, calculations and uncertainty budget.
- Document the lot and certificate used.
- Maintain instrument calibration and measurement assurance.
- Control dilution, mixing, sampling and environmental contamination.
- Evaluate uncertainty contributed by the user’s procedure.
- Keep the chain and evidence available for review.
Use precise commercial language
| Weak or risky phrase | Preferred form |
|---|---|
| NIST-approved PSL spheres | PSL sphere lot supplied with documentation supporting traceability of the stated measurement result to specified references |
| NIST-certified instrument calibration | Instrument calibration performed using reference results with a documented traceability chain, subject to the user’s measurement-assurance system |
| Traceable bottle | Lot-specific certified diameter result with stated method, uncertainty and traceability documentation |
Source control: This page follows NIST’s published traceability policy and FAQ. NIST—not Applied Physics—controls the meaning and permitted use of the NIST name. NIST traceability policy NIST traceability FAQ
Match the standard to the measurement—not the other way around.
Send the instrument, medium, target size, concentration, certificate and packaging requirements to Applied Physics for a technical recommendation.