Tektronix 422, Instruction Manual

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Operating Instructions—Type 422 AC-DC
4. Center the display about the center horizontal line
with the vertical POSITION control.
5. Set the TRIGGERING controls to obtain a stable
display.
6. Set the T IM E /D IV switch to the fastest sweep rate
that will display less than eight divisions between the 10%
and 90% points on the waveform.
7. Determine the 10% and 90% points on the rising por­
tion of the waveform. The figures given in Table 2-3 are fo r
the points 10% up from the start of the rising portion and
10% down from the top of the rising portion (90% point).
TABLE 2-3
Divisions of
display
10% and 90%
points
Divisions vertically
between
10% and 90% points
4
0.4 and 3.6 divisions 3.2
5
0.5 and 4.5 divisions
4.0
6
0.6 and 5.4 divisions 4.8
7
0.7 and 6.3 divisions
5.6
8
0.8 and 7.2 divisions 6.4
8. Adjust the horizontal POSITION control to move the
10% point o f the waveform to the second vertical line of
the graticule. For example w ith a six division display, the
10% point would be 0 6 division up from the start of the
rising portion (see Fig. 2-17).
Fig. 2-17. Measuring risetime.
9. Measure the horizontal distance between the 10% and
90% points. Be sure the VA R IAB LE T IM E /D IV control is
set to CAL.
10. M ultiply the distance measured in step 9 by the
setting of the T IM E /D IV switch. If sweep magnification is
used, divide this answer by 10.
EXAMPLE. Assume that the horizontal distance be­
tween the 10% and 90% points is six divisions (see Fig.
2-17) and the T IM E /D IV switch is set to 1 /is w ith the mag­
nifier on.
Using the time duration formula to find risetime:
Time Duration
(Risetime)
horizontal
distance
(divisions)
T IM E /D IV
setting
magnification
Substituting the given values:
Risetime
6 X 1 jus
10
The risetime if 0.6 microseconds.
Time Difference Measurements
The calibrated sweep rate and dual-trace features o f the
Type 422 allow measurement of time difference between
tw o separate events. To measure tim e difference use the
following procedure:
1. Set the Input Coupling switches to the same position,
depending on the type o f coupling desired.
2. Set the vertical Mode switch to either CHOPPED or
ALT. In general, CHOPPED is more suitable fo r low-
frequency signals and the A L T position is more suitable fo r
high-frequency signals. More information on determining
the mode is given under Dual-Trace Operation in this sec­
tion.
3. Set the TRIGGERING Source switch to CH 1.
4. Connect the reference signal to the INPUT 1 connec­
to r and the comparison signal to the INPUT 2 connector.
The reference signal should precede the comparison signal
in time. Use coaxial cables or probes which have equal time
delay to connect the signals to the INPUT connectors.
5. If the signals are of opposite polarity, pull out the
INVERT switch to invert the Channel 2 display (signals
may be of opposite polarity due to 180° phase difference;
if so, take this into account in the final calculation).
6. Set the VO LTS/DIV switches to produce fo ur or five
division displays.
7. Set the TRIGGERING LEVEL control fo r a stable
display.
8. If possible, set the T IM E /D IV switch fo r a sweep rate
which shows three or more divisions between the two wave­
forms.
9. Adjust the vertical POSITION controls to center each
waveform (or the points on the display between which the