A Comparison Between Time Interval Counter and Dual Mixer Time Difference System for Time Keeping

In order to make a comparison between the time interval counter and the dual mixer time difference measurement system used for time keeping,the measurement results(Rate、RMS、precision and stability of frequency) obtained with the two different measurement devices,the time interval counter SR-620 and the multichannel phase comparator PCOMP,for the same group of atomic clocks in the standard time and frequency laboratory of NTSC(the national time service center of the Chinese academy of sciences) are analyzed.The main conclusion drawn from the analyses is that the comparison precision for the dual mixer time difference measurement is better than that for the time interval counter,and the dual mixer time difference system is more suitable to the measurement of short-term(τ≤5d)stability for hydrogen atomic clocks.