Symmetricom 5071A, Руководство по эксплуатации и программированию

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Chapter 2 Using the 5071A
Steering the Output Frequency
Operating and Programming Manual 23
Steering the Output Frequency
Steering Explained
In normal operation, the output frequencies of the 5071A are in fixed relation to the
Cesium Beam tube response. This relationship provides the basis for traceability of
the 5071A to the international definition of time.
The STEER menu lets you change output frequencies in a calibrated manner with
great precision. Changes can be made manually (front panel), or via the serial
interface (SCPI commands). The 5071A’s output Steerability facilitates its use in
active-clock ensembles. It also gives you a convenient way to make controlled changes
in the phase of the rear-panel sinusoidal and 1pps outputs.
For example, a reserve standard can be brought into phase with a working standard
before the two are interchanged. You can also make changes in the timing of the 1pps
output signal with greater precision than provided by the Slew control’s ± 50 ns
resolution. Simply, Steer the output frequency for a suitable length of time.
The resolution unit of the STEER function is 6.331991 10
-15
, and the range of
the fractional frequency offset is ± 999999 10
-15
. When you STEER the
instrument‘s output frequency, you must take into account the exact amount of
the offset to establish and maintain traceability and accuracy. The frequencies of
the sinusoidal outputs and the rate of the 1pps outputs change by the same
fractional amount when the output is steered.
Use following procedures to add, check, or remove a fractional frequency offset when
using the 5071A:
To Add an Offset
1 Select the STEER menu, then press Enter .
2 Enter the desired fractional frequency offset in units of 1.0 x 10
-15
using the
numeric keypad.
3 Press Enter to initiate the offset, or Prev to cancel the operation and return to
next-higher menu level.
The 5071A rounds the entered offset to the nearest multiple of 6.331991 x 10
-15
,
and displays it when you press Enter . The rounded value is displayed to a
resolution and accuracy of 1 x 10
-15
.
When the output frequency is steered, the ATTENTION light flashes, indicating
that the output frequency and clock rate contain an intentional deviation.
NOTE