Tektronix 323, Instruction Manual

Page: 23 / 170

Operating Instructions— Type 323
the sweep is again triggered by the negative change in sig­
nal level. Continue the counterclockwise movement of the
TRIGGER control and note that triggering occurs at progres­
sively more positive points of the waveform. See Fig. 2-7(B).
Continue the rotation through the control center position.
The trace will disappear or become unstable, then re­
appear, being triggered by the positive change in signal
level. See Fig. 2-7(C). Leave it in this position. (Either AUTO
or manual trigger selection may be used in normal opera­
tion, as determined by the application and the operator's
preference. It is suggested that AUTO be used in most ap­
plications, switching to manual when necessary to improve
stability, increase the low-frequency triggering range, or to
change the triggering point.)
24. Switch the Trig/Horiz Coupling lever to EXT TRIG
OR HORIZ-AC. Note that the trace disappears. At the
side panel, connect the 2 volt peak-to-peak sine wave sig­
nal to the EXT TRIG OR HORIZ INPUT connector. (Keep
the P6049 Probe connected to the 2 volt peak-to-peak sine
wave.) Note that a stabilized trace appears. Decrease the
Fig. 2 -6 . D eterm ining frequency.
19. Slowly rotate the Horizontal POSITION control. Note
that an almost equal number of waveforms can be observed
before and after the occurrence of the waveform which ap­
peared when the X 10 HORIZ MAG was pulled out. This
situation exists because the X 1 0 HORIZ MAG displays the
1 division of trace which straddles the graticule centerline
during X I horizontal operation.
20. Rotate the VARIABLE (TIME/DIV) slowly ccw. Note
that the resultant decrease in sweep speed causes more
square waves to appear. With VARIABLE fully ccw, approx­
imately 4 square wave appear. Return the VARIABLE con­
trol to CAL and the X 1 0 HORIZ MAG to in.
Operating the Trigger Controls
21. Note that the positive portion of the square wave is be­
ing displayed at the beginning of the trace. Switch the
TRIGGER control to — AUTO and observe that the nega­
tive portion of the square wave is being displayed at the
beginning of the trace. The + or — selection determines
whether the horizontal sweep will be triggered by a posi­
tive-going (+ ) or a negative-going (—) signal. In the ab­
sence of a signal, AUTO provides a free-running time base
of relatively constant brightness, regardless of the sweep
rate.
22. Push the X 1 0 VERT GAIN control in and set the
VOLTS/DIV knob to .05. Connect the P6049 Probe to the
VERT INPUT connector. Then connect the probe tip and
ground lead across the output of a low-frequency sine wave
generator. Set the generator for a 2-V peak-to-peak,
60
Hz output. Observe a sine wave which is 4 divisions peak-
to-peak. Note that the beginning of the waveform has a
negative (decreasing) slope. See Fig. 2-7(A).
23. Rotate the TRIGGER control slowly counterclockwise
from the — AUTO position. Note that as the control leaves
the AUTO position, the trace disappears. As the control is
moved further counterclockwise, a point is reached where
.
— Slope trig g e rin g “
selected
:____■____ i____ i i
(A)
TRIGGER
D iffe re n t p o in t
on — slope selected
------ 1------- 1------ 1 ■ i -
IB)
TRIGGER
+ SI ope rigg< ring
** selected
(C)
Fig. 2 -7 . Selection o f trig g e rin g po in t.
2-11