[time-nuts] Cs stability

Pablo Alvarez Sanchez Pablo.Alvarez.Sanchez at cern.ch
Mon Jul 16 13:03:36 EDT 2007


I am curious about the total stability of Cs clocks. Normally producers give you an initial accuracy after 30 minutes of power on and a table with the Allan deviation for different measurement intervals. 

After that they give you the environmental and physical specifications. For the hp5071 you have:

General environment
Operating 0°C to 55°C
Non-operating -40°C to 70°C
Humidity 0 to 95%RH (45C max)
Magnetic field dc, 55, 60Hz 0 to 2 gauss peak - any orientation Atmospheric pressure £1E-13 change in frequency for pressure down to 19kPa (equivalent to an altitude of 12.2km) Shock and vibration Mil-T-28800D, Type III, class 5 Hammer Blow Shock Test, Mil-S-901C, Grade A, Class 1, Type A Mile-STD, 167-1 (phase noise)
EMI: Conducted and radiated emissions per CISPR 11/EN 55011, Group 1, Class A
EMC: per MIL-STD-461C, Part 7, Class B dc magnetic field up to 7.8 Gauss

My questions are:

Are the Allan deviation specs also valid for all the environmental range, including shock and vibration, or only for lab conditions?

In the article "OBSERVATIONS ON STABILITY MEASUREMENTS OF COMMERCIAL ATOMIC CLOCKS", Pekka Eskelinen claims to have measured a phase temperature coefficient of 100ns/degree for commercial Cs clocks in 1999.

http://ieeexplore.ieee.org/iel5/6762/18075/00840739.pdf (If you cannot read it I can try to send you a copy by email)

Has any of you ever measured such a coefficient?




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