HP 54645A, User'S And Service Manual

Page: 185 / 301

To trigger on odd or even fields
To check the envelope of your video signals, or to measure worst case
distortion, trigger on the odd or even fields. When Field 1 is selected, the
oscilloscope triggers on color fields 1 or 3. When Field 2 is selected, the
oscilloscope triggers on color fields 2 or 4.
1
Select the TV display, TV as the trigger mode, and the appropriate TV
standard as described in the section, "To autoscale on a video signal."
2
Press
Slope/Glitch
in the
TRIGGER
section of the front panel,
then press the TV and TV Menu softkeys. Press Field 1 or Field 2 .
The trigger circuits look for the position of the start of Vertical Sync to
determine the field. But this definition of field does not take into
consideration the phase of the reference subcarrier. When Field 1 is selected,
the trigger system will find any field where the vertical sync starts on Line 4.
In the case of NTSC video, the oscilloscope will trigger on color field 1
alternating with color field 3 (see the following figure). This setup can be
used to measure the envelope of the reference burst.
Triggering on Color Field 1 Alternating with Color Field 3
Figure 6-5
Using Option 005 Enhanced TV/Video Trigger (HP 54645A)
To trigger on odd or even fields
6-10