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Stanford SR625 Frequency Counter with Rb Timebase

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Stanford SR625 Frequency Counter with Rb Timebase

Stanford Research Systems

The SR625 Frequency Counter is a NIST traceable frequency counting standard for calibrating base stations, transmitters and many other types of communiction systems. It combines the high resolution and wide variety of features found in the SR620 counter with the atomic accuracy of a rubidium timebase.


  • Rubidium atomic timebase
  • 2GHz prescaler input
  • 11-digit frequency resolution (1s)
  • 10MHz Rb timebase output
  • Statistical analysis and Allan variance
  • Hardcopy to printers
  • GPIB and RS232 interfaces

The SR625 Frequency Counter consists of a frequency counter (SR620), a high-accuracy rubidium timebase (PRS10), and a 2GHz input prescaler. The combination of the SR620 and the prescaler allows direct frequency measurements up to 2GHz with twelve digits of resolution in a 100s measurement. The rubidium timebase ensures excellent short-term stability (<2 x 10-11 Allan variance <1s>) and long-term drift (<5 x 10-11/month).


          SR625 datasheet                                            Read more on Stanford's website