Agilent Technologies DSO-X 4022A, Руководство пользователя

Страница: 193 / 488

Triggers
10
Agilent InfiniiVision 4000 X-Series Oscilloscopes User's Guide 193
• For interleaved video, enabling the Horiz Sync control and setting the
Horiz Sync adjustment to the sync time of the probed video signal
allows the
Edge #
function to count only lines and not double count
during equalization. Additionally, the Field Holdoff can be adjusted so
that the oscilloscope triggers once per frame.
• Similarly, for progressive video with a tri- level sync, enabling the
Horiz Sync
control and setting the
Horiz Sync
adjustment to the sync
time of the probed video signal allows the Edge # function to count
only lines and not double count during vertical sync.
When the horizontal sync control is enabled, press the second
Horiz Sync
softkey; then, turn the Entry knob to set the minimum time the
horizontal sync pulse must be present to be considered valid.
To trigger on a specific line of video
Video triggering requires greater than 1/2 division of sync amplitude with
any analog channel as the trigger source. Turning the trigger
Level
knob in
Video 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
Press the
[Trigger]
key.
2
In the Trigger Menu, press the
Trigger
softkey; then, turn the Entry knob
to select Video .
3 Press the Settings softkey, then press the Standard softkey to select the
appropriate TV standard (NTSC).
4
Press the
Mode
softkey and select the TV field of the line you want to
trigger on. You can choose Line:Field1 , Line:Field2 , or Line:Alternate .
5 Press the Line # softkey and select the number of the line you want to
examine.
N O T E
Alternate Triggering
If Line:Alternate 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.