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Measurements of time and frequency are not only very popular kind of measurements but also the most precise kind of measurements. We should mention, that the ratio error of reproduction of the unit of time of second with the help of the most precise installations is ~10-14...10-15, what is nearly six times better than the closest by value error of reproduction of kg mass unit (10-9). The progress is continuing, and it is already predicted the decreasing of the error of second reproduction up to ~10-17...10-18. thanks to the use of quantum standards in the optical range and development of new technologies of measurements of their frequencies.

Very unique is also the variety of use of this kind of measurements. In the everyday life these are milliards of hours, in economy . systems of monitoring of technology processes, connection systems, information and measuring complexes and finally aerospace systems. The units of time and frequency are reproduced and stored with the help of measurement standards. The national primary standard of the units of time and frequency, created at NSC gInstitute of Metrologyh, contains a number of basic and additional complexes which are working steadily or according to the determined schedule. 

The base of the standard is a group of keepers of time and frequency in the content of one cesium and five hydrogen standards of frequency. Atomic second is determined as a time interval during which 9 192 631 770 vibrations of  cesium standard are performed. According to the results of a group of keepers, there is formed national scale of coordinated time of Ukraine UTC (UA). Deviation between national scale of coordinated time UTC (UA), which is reproduced with a help of national primary standard and International scale of coordinated time UTC is ±0,1 μs.

The complex of the standard is located in the special equipped rooms. In the rooms with hydrogen standards there is a stable temperature ±1 °C. For the continuous apparatus supply there exists a special sub-complex, including the appropriate systems of automatic sources switching.

For confirmation of metrological characteristics of the standard there are conducted external comparisons with the standards of other countries with the use of signals of satellite radio navigation systems.

Continuous comparisons with the standards of other countries show the standard has ratio instability of frequency ~(2-3)·10-14 at daily time interval.

The National (state primary) standard of time and frequency units is the basis of the Main Center Service of Universal Time and Reference Frequencies in Ukraine. As part of the service, metrological control of reference signals of time and frequency transmitted by various technical means is carried out by comparing their metrological characteristics with the characteristics of the standard. In addition, the size of the unit is transmitted to consumers through computer systems and communication lines. Information on the results of control and characteristics of the standard is covered on the website of the NSC "Institute of Metrology" on the Internet.