Delayed Sweep Magnification - Tektronix 7B51 Instruction Manual

Pulse to be
magnified
/
lI'
- -
Fig. 2·13. Using delayed sweep for sweep magnification.
Time Difference
=
(7.73 - 2.23) X 5 l1s.
The time difference is 27.5 microseconds.
Delayed Sweep Magnification
The delayed sweep feature of the Type 7851 can be
used to provide higher apparent magnification than is
provided by the MAG switch. The sweep rate of the
DELAYED SWEEP (8 sweep) is not actually increased; the
apparent magnification is the result of delaying the 8 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 8 TIME/DIV
switch. The following method uses the 8 STARTS AFTER
DE LAY 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
AL T to display both Time-8ase sweeps.
2. Set the VOL TS/DIV selector to produce a display
about three divisions in amplitude.
3., Set the A Time-8ase 8 DELAY MODE selector to 8
STARTS AFTER DELAY. Adjust the A Triggering controls
for a stable display.
®
Operating Instructions-Type 7851
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 8 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 8 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 8 TIME/DIV setting of 1 l1S is:
Apparent Magnification
(Delayed Sweepf
Substituting the given values:
Apparent
Magnification
A TIME/DIV setting
8 TIME/DIV setting
1 X 10-
4
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
8 TRIGGERA8LE AFTER DELAY position of the 8
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 8 DELAY MODE selector to 8 TRIGGER-
A8LE AFTER DELAY.
3. Adjust the 8 LEVEL control so the intensified
portion on the trace is stable.
4. Inability to intensify the desired portion indicates
that the 8 Triggering controls are incorrectly set or the
2-17