--- metadata: title: 'Resolutions of the CGPM: 19th meeting' date: '1991-10-03' source: BIPM - Pavillon de Breteuil url: https://www.bipm.org/en/CGPM/db/19 resolutions: - dates: - '1991-10-03' title: Time standards and time comparisons identifier: 1 url: https://www.bipm.org/en/CGPM/db/19/1/ reference: https://www.bipm.org/utils/common/pdf/CGPM/CGPM19.pdf#page=183 approvals: - type: affirmative degree: unanimous message: The 19th Conférence Générale des Poids et Mesures, considerations: - type: noting date_effective: '1991-10-03' message: noting that the accuracy of clock comparisons has been greatly improved by the use of satellite techniques, actions: - type: affirms / reaffirming date_effective: '1991-10-03' message: |- remarks that this accuracy can be further improved by the better use of the satellite techniques already developed, reveals the differences and systematic variations among atomic frequency standards, allows a better synchronization of national time scales, - type: recommends date_effective: '1991-10-03' message: recommends the construction of new primary caesium standards, the improvement of the frequency accuracy of existing primary standards and the study of the systematic differences in frequency which exist between them, - type: recommends date_effective: '1991-10-03' message: recommends that the laboratories participating in International Atomic Time (TAI) stabilize the environmental conditions of each contributing clock, keep careful records of these environmental conditions and report them to the BIPM, - type: recommends date_effective: '1991-10-03' message: recommends that the coordinates adopted for antennas used in single-way time comparison by satellite techniques correspond to their real position in the terrestrial reference system of the International Earth Rotation Service. - dates: - '1991-10-03' title: The Josephson and quantum-Hall effects identifier: 2 url: https://www.bipm.org/en/CGPM/db/19/2/ reference: https://www.bipm.org/utils/common/pdf/CGPM/CGPM19.pdf#page=184 approvals: - type: affirmative degree: unanimous message: The 19th Conférence Générale des Poids et Mesures, considerations: - type: considering date_effective: '1991-10-03' message: considering that worldwide uniformity and long-term stability of the national representations of electrical units are of great importance for science, industry and commerce for both technical and economic reasons, - type: considering date_effective: '1991-10-03' message: considering that many national laboratories now use the Josephson and quantum-Hall effects for the conservation of their representations of the volt and the ohm respectively, a practice giving complete security in terms of long-term stability, - type: considering date_effective: '1991-10-03' message: considering that the values attributed to their representations should be in as close as possible agreement with the SI, - type: recalling / further recalling date_effective: '1991-10-03' message: recalling cgpm-resolution:en/18/6[Resolution 6 of the 18th Conférence Générale] concerning adjustments then foreseen in representations of the volt and the ohm, - type: noting date_effective: '1991-10-03' message: noting the decisions made by the Comité International des Poids et Mesures in 1988, during its 77th Meeting concerning these adjustments, in particular the conventional values stem:[K_(J-90)] (equal to stem:[483 597","9 "GHz"/"V"]) and stem:[R_(K-90)] (equal to stem:[25 812","807 sf Omega ]) attributed to the Josephson constant stem:[K_("J")] and the von Klitzing constant stem:[R_("K")] used in representations of the volt and the ohm respectively, actions: - type: recommends date_effective: '1991-10-03' message: recommends that national laboratories continue their efforts to reduce the uncertainty in the knowledge of the ratios stem:[K_(J-90)/K_("J")] and stem:[R_(K-90)/R_("K")], - type: recommends date_effective: '1991-10-03' message: recommends that research be continued into the basic theory of the Josephson and quantum-Hall effects. - dates: - '1991-10-03' title: The International Temperature Scale of 1990 (ITS-90) and future work in thermometry identifier: 3 url: https://www.bipm.org/en/CGPM/db/19/3/ reference: https://www.bipm.org/utils/common/pdf/CGPM/CGPM19.pdf#page=185 approvals: - type: affirmative degree: unanimous message: The 19th Conférence Générale des Poids et Mesures, considerations: - type: considering date_effective: '1991-10-03' message: considering that worldwide uniformity and long-term stability in the measurement of temperature are of great importance for science, industry and commerce for both technical and economic reasons, - type: considering date_effective: '1991-10-03' message: considering that the international temperature scale should be as close as possible to thermodynamic temperature, - type: noting date_effective: '1991-10-03' message: |- noting that the cgpm-resolution:en/18/7[18th Conférence Générale in its Resolution 7] had invited the Comité International des Poids et Mesures and national laboratories to prepare and adopt a new international scale to replace the International Practical Temperature Scale of 1968, by then known to differ significantly from thermodynamic temperatures, that the International Temperature Scale of 1990 (ITS-90) adopted by the Comité International in 1989 at its 78th Meeting is generally more precise, more readily realized and more nearly in accord with thermodynamic temperatures, and that it fulfills the requirements demanded of it by Resolution 7 of the 18th Conférence Générale, actions: - type: recommends date_effective: '1991-10-03' message: recommends that national laboratories continue their efforts to improve the worldwide uniformity and long-term stability in the measurement of temperature by the rapid implementation of the ITS-90 and the maintenance of research programmes on fundamental thermometry. - dates: - '1991-10-03' title: SI prefixes zetta, zepto, yotta and yocto identifier: 4 url: https://www.bipm.org/en/CGPM/db/19/4/ reference: https://www.bipm.org/utils/common/pdf/CGPM/CGPM19.pdf#page=185 approvals: - type: affirmative degree: unanimous message: The 19th Conférence Générale des Poids et Mesures (CGPM), considerations: [] actions: - type: decides date_effective: '1991-10-03' message: |- decides to add to the list of SI prefixes to be used for multiples and submultiples of units, adopted by the 11th CGPM, cgpm-resolution:en/11/12#para3[Resolution 12], paragraph 3, the 12th CGPM, cgpm-resolution:en/12/8[Resolution 8], and the 15th CGPM, cgpm-resolution:en/15/10[Resolution 10], the following prefixes: |=== .<| Multiplying factor .<| Prefix .<| Symbol 3+| .<| stem:[10^(21)] .<| zetta .<| Z .<| stem:[10^(-21)] .<| zepto .<| z .<| stem:[10^(24)] .<| yotta .<| Y .<| stem:[10^(-24)] .<| yocto .<| y |===