Connection to the Network
45
Note: Theoretically, testing could start before the end of the position averaging
process. The improved time estimation due to this function would be automatically
applied starting from the end of the auto-averaging process.
2.6.3. Using the Holdover Mode
xGenius units carrying OCXO and Rubidium oscillators can operate in holdover mode.
They can be disconnected from the clock reference input and they still keep accurate
frequency and phase for a period of time that ranges from a few minutes for OCXO
units or a few hours in Rubidium units. The holdover mode cannot be used in TCXO
units.
The holdover mode is useful when, for some reason, there is not a suitable clock
reference that could be used in the test site In this case, the equipment could be
synchronized to a GNSS or any other clock source far from the test site and driven to
holdover.The results are accurate within a period of time as long as the test unit is not
restarted
To enable the holdover operation in xGenius, follow these steps:
1. Connect and configure the clock reference input in your test unit to GNSS or any
of the 1 PPS, 1 PP2S or ToD interfaces (See section 2.6).
Note: Holdover from a frequency reference is not supported.
2. For optimum performance, in Rubidium units, wait for at least two hours once the
test unit is locked to the clock reference input. In OCXO units no additional waiting
time is necessary once the equipment is locked.
Note: Theoretically, the unit could the driven to holdover when it is still in a Fine
locking state but the accuracy level will be lower if this is done.
3. From the Home panel, go to CONFIG,
The port setup panel is displayed.
4. Go to Reference clock.
5. Go to oscillator.
6. Optionally, configure Holdover duration to the time you want to keep the unit in
holdover. The unit will go to a Holdover timeout once this time is reached and
frequency / time traceability will be lost.
7. Configure Force holdover to Yes
An small H is displayed in the screen to show that the unit has entered in
holdover.
8. Optionally, unplug the clock reference input from the test unit.
The REF LED now displays the red colour. The unit is ready for testing.
In Rubidium units, it is possible to recover from a holdover without restarting the
oscillator control loop from the beginning. This is the right procedure to do that:
1. Plug a GNSS or 1 PPS clock reference to the right connector in your xGenius
tester.
2. Make sure that the equipment is receiving the reference (green REF LED)
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