Agilent Technologies 8935 Series, Руководство пользователя

Страница: 170 / 343

Chapter 7 169
Periodic Adjustments
Setting the Timebase Latches
Setting the Timebase Latches
The
refs_DAC_coarse
and
ref_DAC_fine
values adjust the frequency
of the Test Set’s internal 10 MHz reference. They are stored in memory.
The controller reads the values and sends the appropriate adjustment
to the A2A23 Reference assembly.
The following procedure is to be used when running the program
“Timebase Reference Using a Counter” on page 165 .
1. Press
Shift
,
Duplex Config
to access the CONFIGURE screen.
2. Select
SERVICE
under the
To Screen
menu.
3. Connect a frequency counter to the rear-panel 10 MHz REF
OUTPUT connector.
4. Select the
Latch
field.
5. Select
refs_DAC_coarse
under the
Choices:
menu.
6. Select the
Value
field.
7. Rotate the knob until the counter reads as close to 10 MHz as
possible.
8. Select the
Latch
field.
9. Select
refs_DAC_fine
under the
Choices:
menu.
10.Select the
Value
field.
11.Rotate the knob until the counter reads as close to 10 MHz as
possible.
12.Store the new DAC values (timebase calibration data) in non-volatile
memory by selecting and running the
Timebase Reference Using
a Counter
routine from the Periodic Calibration Menu. See
“Timebase Reference Using a Counter” on page 165 .