Recommendation 2 of the 16th CCTF (2004)

Concerning the reporting and use of primary frequency standards

The Consultative Committee for Time and Frequency,

considering that

• CCTF Recommendation S 3 (1999) provides guidelines to report the results of primary frequency standards and their uncertainties,
• the proper usage of primary frequency standards measurements is essential to ensure a correct estimation of the scale unit of International Atomic Time (TAI),
• it is desirable that this estimation be based on a sufficient number of measurements from different primary frequency standards,
• the uncertainty of each measurement should be adequately documented and the methods of its estimation should be described,
• it is desirable that all primary frequency data be archived and made available publicly,

recommends that

• laboratories that develop primary frequency standards operate them on a regular basis to realize the SI second and provide to the International Bureau of Weights and Measures (BIPM) results of comparisons of the primary frequency standard with a clock contributing to TAI,
• the uncertainty statements of each primary standard either refer to the publication of all corrections, their methods of evaluation and descriptions of all instrumentation, or itself constitute such a publication [Recommendation S 3 (1999)],
• all successive evaluations of a primary frequency standard be accompanied by a report describing any changes since the first referenced full evaluation, as well as all elements which are specific to each evaluation,
• this documentation be archived by the BIPM and made publicly available,
• the evaluations be used for steering of TAI, unless deemed detrimental to TAI in a mutual decision by the concerned laboratory and the BIPM
• the Working Group on the Expression of Uncertainties in Primary Frequency Standards (PFS) reviews the use of all reported evaluations of PFS.

DOI : 10.59161/CCTF2004REC2E