Delayed Sweep Time Measurements - Tektronix 7B51 Instruction Manual

Operating Instructions-Type 7851
horizontal
distance
(divisions)
x
TIME/DIV
setting
Time Duration
(Risetime)
magnification
Substituting the given values:
Risetime
=
4 X 1
]ls
10
The risetime is 0.4 microsecond.
Delayed Sweep Time Measurements
The delayed sweep mode can be used to make accurate
time measurements. The following measurement determines
the time difference between two pulses displayed on the
same trace. This application may also be used to measure
time difference from two different sources (dual·trace) or
:0
measure time duration of a single pulse. See Section one
ior
measurement accuracy.
1. Connect the signal to either vertical plug-in. Set the
Indicator Oscilloscope vertical MODE selector to disPidY
the plug-in being used. Set the horizontal MODE selector to
CHOP or AL T (see Oscilloscope Manual discussion on hori-
zontal mode switching) to display both Time-Base sweeps.
2. Set the VOL TS/DIV selector to produce a display
about three divisions in amplitude (see Fig. 2-12).
DELAY TIME MULTIPLIER
dial:
223
DELAY riME MULTIPLIER
dial:
\ III!
time difference
7.73
~ ·f
\
~'
\
r
:(
-
I
Ii
J
~
~
Fig. 2-12. Measuring time difference using delayed sweep.
2-16
3. Set the A TIME/DIV to a sweep rate which displays
about six divisions between pulses. Adjust the A Triggering
controls for a stable display.
4. Set the A Time-Base B DELAY MODE selector to B
STARTS AFTER DELAY.
5. Set the B Time/div to a setting 1/100 of the A TIME/
DIV sweep rate. This produces an intensified portion about
0.1 division in length.
NOTE
Do not change the A LEVEL control setting or the
horizontal POSITION control setting in the fol/owing
steps, as the measurement accuracy will be affected.
6. Turn the DELAY-TIME MULTIPLIER dial to move
the intensified portion of the A sweep to the first pulse.
7. Adjust the DELAY-TIME MULTIPLIER dial to move
the pulse (or rising portion) of the B sweep to the center
vertical line. Note the setting of the DELAY-TIME MUL TI-
PLIER dial.
8. Turn the DELAY-TIME MULTIPLIER dial clockwise
until the second pulse is positioned to this same point
(if
several pulses are displayed, observe the intensified portior
of the A sweep to locate the correct pulse). Again note thE
dial setting.
9. Subtract the first dial setting from the second and
multiply by the delay time shown by the A TIME/DIV
selector. This is the time interval between the pulses.
Example: Assume the first dial setting is 2.23 and the
second dial setting is 7.73 with the TIME/DIV set to 5
]lS
(see Fig. 2-13). .
Using the formula:
Time Difference
(delayed sweep)
second dial
setting
Substituting the given values:
first dial delay time
X (A TIME/DIV
setting
setting)
®