VIRTUAL CLOCK AT CENAM

With the aim to improve the metrological characteristics of the time scale UTC(CNM), the Time and Frequency Division of the Centre Nacional de Metrologia, CENAM, has developed a Virtual Clock in terms of the time differences among atomic clocks under operation at their facilities. The mathematical algorithm used in the generation of the CENAM´s virtual clock is similar to one proposed by NIST. A servo control is used to make corrections on the frequency output of an active Hydrogen Maser in order to have a physical frequency signal matching the metrological characteristics, as best as possible, of the virtual clock frequency.