Tektronix VM700T, User Manual

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Waveform Mode
3- 12
VM700T Option 01 (NTSC) & Option 11 (PAL) User Manual
Note that the measurement set bandwidth limits the signal to 6 MHz. To
accurately display rise times of signals with significant frequency components
between 5 MHz and 6 MHz, select Precision mode.
To Use Cursors to Measure a Rise or Fall Time. First, use the control knob and the
Vertical/Horizontal buttons to position the leading edge of a sync pulse in the
center of the screen and then expand the sync edge to fill about 80% of the
screen. Select the Reset Cursors soft key to center the cursors, reset the
amplitude reference markers, and turn off any previously selected cursor Lock
soft keys.
Attach the left amplitude reference marker to a stable spot on the blanking level
prior to the leading edge of sync by moving the waveform to the right until the
blanking level reaches the cursor. This establishes the 100% point of sync. Then
attach the right amplitude reference marker to a stable spot on the sync tip by
moving the waveform to the left until the sync tip reaches the cursor. This
establishes the 0% point of sync. Live video may require moving the sync edge a
little further in both directions to find an average or stable level for the 100% and
0% points. When the sync edge is now moved past the cursors, the % point
readout is calibrated, and indicates the sync edge % point that intersects the
cursors.
NOTE
. If the waveform point that the amplitude reference marker is attached to is
moved off the display, the amplitude reference marker does not remain attached
to the waveform. Instead, it locks to the vertical scale at the point where the
waveform left the display.
So, if the level of the signal at the point where the amplitude reference marker
was formerly anchored (which is now off screen) changes, the amplitude
reference marker will not track that change. It may sometimes be necessary to
decrease the horizontal expansion to keep both amplitude reference markers on
the display when trying to find a stable point on live video to anchor them.
Position the sync edge under the cursors so the % point readout is 90% and
select the Lock Left soft key. This locks the left cursor to the 90% point of the
sync edge. Now when you move the sync edge horizontally the left cursor moves
with it. Notice that the left cursor is a solid vertical line, and the right cursor,
which is still centered in the display, is a dashed line. Now simply move the
waveform so the % point readout indicates 10%. The Time from L to R readout
now indicates the rise time of the leading edge of sync. Figure 3--3 illustrates the
right cursor sitting at the 10% point and the left cursor locked to the 90% point
of the sync edge.
Note that touching either the Center Left or Center Right soft key will move the
corresponding cursor to the center of the display.
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