phase offset between reference 1PPS and system 1PPS, as it may occur when
going back into sync to the external reference after a long holdover. A
Restart
Tracking
will re-align the system 1PPS with the reference 1PPS very quickly, but
may cause the 1PPS output to jump.
Recalibrate
: In rare cases, existing calibration data may no longer be suitable to
calibrate the oscillator. This function will delete the existing calibration data, and
begin a new calibration process (not applicable for low phase-noise Rubidium
oscillators).
1PPS Phase Validation
: Turn ON Smart Reference Monitoring. See "Reference
Monitoring: Phase" on page 272.
4.
Click Submit.
3.5.2.1
Time Figure of Merit (TFOM)
The TFOM reflects the
estimated error
range values between the
reference 1PPS
(such as GPS
1PPS) and the
System 1PPS
which is being aligned to the 1PPS. The estimated error is referred
to as the 1PPS Phase error. TFOM values are ranges of these phase errors. The larger the
phase error estimate, the larger the TFOM value will be. For example, TFOM 3 is reported
when the estimated phase error is any value between 10 ns to less than 100 ns of the offset
between the selected 1PPS reference and the system’s 1PPS.
TFOM is NetClock’s estimation of how accurately it is synchronized with its time and 1PPS ref
erence inputs, based on several factors, known as the
Estimated Time Error
or ETE. The larger
the TFOM value, the less accurate NetClock believes it is aligned with its 1PPS input that is used
to perform disciplining. If this estimated error is too large, it could adversely affect the per
formance of oscillator disciplining. The available TFOM range is 1 through 15. You may refer
to the following for the TFOM to ETE conversions:
Table 3-5:
TFOM to ETE conversion
Reported TFOM Value
Estimated Time Error (ETE)
1
<= 1 nsec
2
1 nsec < ETE <= 10 nsec
3
10 nsec < ETE <= 100 nsec
4
100 nsec < ETE <= 1 μsec
5
1 μsec < ETE <= 10 μsec
6
10 μsec < ETE <= 100 μsec
7
100 μsec < ETE <= 1 msec
8
1 msec < ETE <= 10 msec
9
10 msec < ETE <= 100 msec
10
100 msec < ETE <= 1 sec
3.5 Managing the Oscillator
CHAPTER
3
•
NetClock User Reference Guide
Rev.
16
217
Summary of Contents for NetClock 9400 Series
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