Triggering 4
InfiniiVision Oscilloscopes User’s Guide 163
T
RIGGERING ON ALL FIELDS
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 Press the Trigger [More] key, then press the TV softkey.
2 Press the Settings softkey, then press the Standard softkey to select the appropriate
TV standard.
3 Press the Mode softkey and select Field1 or Field2.
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.
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