2. Connection diagram and national references

Advances in instrumentation, particularly in the field of 0-360° references, have profoundly altered the structure of the calibration chain.

In the 1980s-1990s, new references appeared that were able to position themselves continuously over one or more laps, with uncertainties of the order of a hundredth of a second, or a few thousandths.

In fact, it was no longer necessary to combine discretely positioned references on a lathe (as in the case of indexing tables) with interpolator systems based on sine methods (figure 1 ).