HP 54645A, User'S And Service Manual

Page: 180 / 301

To trigger on a specific line of video
TV triggering requires greater than 1/4 division of sync amplitude, either
channel 1 or channel 2 as the trigger source. Turning the trigger level knob
in TV trigger does not change the trigger level because the trigger level is
automatically set to the sync pulse tips.
One example of triggering on a specific line of video is looking at the vertical
interval test signals (VITS), which are typically in line 18. Another example
is closed captioning, which is typically in line 21.
1
Select the TV display, TV as the trigger mode, and the appropriate
TV standard.
2
Press
Slope/Glitch
in the
TRIGGER
section of the front panel,
then press the
TV
and
TV Menu softkeys. Press Line
. Select the
number of the line you want to examine.
3
Press the
Trigger On Field
softkey to select the TV field of the line you
want to trigger on. Your choices are
Field 1
,
Field 2
, and
Alt Fld
(Alternate Fields).
Alternate Triggering
If Alt Fld is selected, the oscilloscope will alternately trigger on the selected line
number in Field 1 and Field 2. This is a quick way to compare the Field 1 VITS
and Field 2 VITS or to check for the correct insertion of the half line at the end of
Field 1.
When using
GENERIC
as the TV standard, the Trigger On Field softkey gives
you the choices of Field 1, Field 2 and Vertical.
Using Option 005 Enhanced TV/Video Trigger (HP 54645A)
To trigger on a specific line of video
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