Delayed Sweep Magnification - Tektronix 7B51 Instruction Manual

Fig. 2-13 . Using delayed sweep for sweep magnification .
'rime Difference = (7 .73 - 2 .23) X 5 ps.
The time difference is 27 .5 microseconds .
Delayed Sweep Magnification
The delayed sweep feature of the Type 71351 can be
used to provide higher apparent magnification than is
provided by the MAG switch . The sweep rate of the
DELAYED SWEEP (B sweep) is not actually increased; the
apparent magnification is the result of delaying the B sweep
an amount of time selected by the A TIME/DIV switch and
the DELAY-TIME MULTIPLIER dial before the display is
presented at the sweep rate selected by the B TIME/DIV
switch . The following method uses the B STARTS AFTER
DELAY position to allow the delayed portion to be posi-
tioned with the DELAY-TIME MULTIPLIER dial . If there
is too much jitter in the delayed display, use the Triggered
Delayed Sweep Magnification procedure.
1 . Connect the signal to either vertical plug-in. Set the
Indicator Oscilloscope vertical MODE selector to display
the plug-in used and the horizontal MODE to CHOP or
ALT to display both Time-Base sweeps .
2. Set the VOLTS/DIV selector to produce a display
about three divisions in amplitude .
3., Set the A Time-Base B DELAY MODE selector to B
STARTS AFTER DELAY. Adjust the A Triggering controls
for a stable display.
Operating Instructions-Type 71351
4. Set the A TIME/DIV to a sweep rate which displays
the complete waveform .
5. Position the start of the intensified portion with the
DELAY-TIME MULTIPLIER dial to the part of the display
to be magnified .
6. Set the B TIME/DIV to a setting which intensifies the
full portion to be magnified . The start of the intensified
trace remains as positioned above.
7 . Time measurements can be made from the display in
the conventional manner . Sweep rate is determined by the
setting of the B TIME/DIV selector .
Example: The apparent magnification of the display
shown in Fig. 2-13 with an A TIME/DIV setting of .1 ms
and a B TI ME/DIV setting of 1 lis is :
Apparent Magnification __ A TIME/DIV setting
(Delayed Sweep) B TI ME/DIV setting
Substituting the given values :
Apparent
_ 1 X 10 -4
Magnification 1 X 10 -6
=
100
The apparent magnification is 100 times .
Triggered Delayed Sweep Magnification. The delayed
sweep magnification method just described may produce
too much jitter at high apparent magnification ranges . The
B TRIGGERABLE AFTER DELAY position of the B
DELAY MODE selector provides a more stable display,
since the delayed display is triggered at the same point each
time .
1 . Set up the display as given in steps 1 through 6
above .
2. Set the B DELAY MODE selector to B TRIGGER-
ABLE AFTER DELAY .
3. Adjust the B LEVEL control so the intensified
portion on the trace is stable .
4. Inability to intensify the desired portion indicates
that the B Triggering controls are incorrectly set or the
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