Open Access
Review
Table 1
Metrological ladder for the SI (example: length).a
| Traceability | Today | New SI |
|---|---|---|
| Top | Definitional method. Method using “distance“ and “time interval” |
No definitional method. Condition: to reproduce the stipulated constant(s) value |
| –1 | Mise en pratique. Other method(s): frequency and period |
“Primary” methods. c0 and t explicitly in the model |
| –2 | Secondary methods. Other method(s): stabilised laser |
Mise en pratique. Other method(s): frequency and period |
| –3 | Workshop methods. Gauge blocks |
Secondary methods. Other method(s): stabilised laser |
| –4 … |
Lower ranks … |
Workshop methods: gauge blocks, … |
a
See term in [6].
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