Tektronix 585 - Page 17

Operating Instructions — Type 585
OUTPUT OF THE EXTERNAL
EQUIPMENT IS APPLIED TO THE
OSCILLOSCOPE INPUT.
FREE-RUNNING SWEEP
GATE OR SAWTOOTH WAVE 
FORMS ARE CONNECTED TO THE
EXTERNAL EQUIPMENT.
EQUIPMENT TO BE TRIGGERED
OR SYNCHRONIZED BY THE
OSCILLOSCOPE.
in some applications it may be more desirable to reverse the
process and initiate the input waveform through use of a
periodically recurrent waveform from the oscilloscope. In
this type of application the sweep is caused to free-run
and an output from either the -(-GATE OUT or SAW 
TOOTH A front panel connectors is used to trigger or
synchronize the input waveform.
The Time Base B may be used as a trigger-rate-generator
while the Time Base A is used in its normal fashion.
Either Time Base can be made to free run by rotating its
STABILITY control fully clockwise. Under these conditions
the sweep runs at a rate determined by the setting of the
TIME/CM controls.
In this application it is advisable to place the TRIGGER 
ING SOURCE switch in its EXT. position to prevent the
vertical signal from producing any interference or jitter.
In addition to providing the means for triggering or syn 
chronizing an external piece of equipment, a free-running
sweep also provides a convenient reference trace on the
oscilloscope screen without requiring an input signal. The
trace can then be used to establish a voltage reference line.
Fig. 2-10. Using the Gate or Sawtooth output waveforms to syn 
chronize or trigger external equipment.
Time Base A Synchronized High Frequency
Operation
If it is necessary to observe a high frequency repetitive
waveform, too low in amplitude to produce a stable trig 
gered display, a special adjustment can be made to permit
synchronizing the Type 585 with the low level signal. Remove
the right side panel of the oscilloscope. Find R47, the TRIG.
SENS, control, located right under the forward carrying
handle. Note its setting, then rotate it fully clockwise.
(Figure 2-9).
With the TRIG. SENS, control fully clockwise, the tunnel
diode trigger regenerator will oscillate at certain settings
of the front panel TRIGGERING LEVEL control. This mode
of operation permits the vertical information to synchronize
the tunnel diode oscillation rate and cause the sweep gen 
erator to present a stable display. When synchronizing the
sweep, place the STABILITY control in its PRESET position,
then apply the vertical signal, and rotate the TRIGGERING
LEVEL control for a stable presentation.
Note that once the internal TRIG. SENS, control has been
rotated clockwise, the tunnel diode trigger regenerator can
be made to cause a sweep at some positions of the TRIG 
GERING LEVEL control in the absence of a triggering signal.
It is best to restore the TRIG. SENS, control to its proper
triggerable position you previously noted, and as described
in the Calibration section of this manual. Replace the right
side panel once synchronized operation is completed.
Free-Running Sweep Operation of either A or B
Sweep
In the usual oscilloscope application, the sweep is trig 
gered or synchronized by the input waveform. However,
Single Sweep Operation
The usual oscilloscope display formed by a repetitive
sweep is best for most applications. However, in applica 
tions where the displayed waveform is not repetitive or
varies in amplitude, shape, or time interval, a repetitive
sweep produces a jumbled display. When observing a
waveform of this type, it is usually best to use a single sweep
presentation.
The Type 585 Oscilloscope permits a single sweep pre 
sentation. The single sweep feature is selected by placing
the HORIZONTAL DISPLAY switch in the "A" SINGLE SWEEP
position. In this position, only Time Base A can produce a
single sweep. The RESET button controls the operation of
the single sweep.
When the A Sweep STABILITY control is set fully clock 
wise, a single sweep runs immediately each time the RESET
button is depressed. When the STABILITY control is set for
triggered operation, the single sweep does not occur when
the RESET button is depressed until a triggering signal is
applied. Instead the READY lamp lights to indicate that
the sweep is ready to be triggered. When a triggering
signal occurs, the sweep runs once and the READY light
goes out. Each time the RESET button is depressed the
procedure is repeated.
When operating the Type 585 in the single sweep mode
the apparent brilliance of the crt trace will be less than dur 
ing repetitive sweep operation. This is due to both the crt
phosphor and your eye persistence making a repetitive
sweep look brighter than each individual sweep is. In an
attempt to increase the single sweep brilliance you may turn
up the intensity control too high. There is a point (that varies
a bit between different instruments) of maximum intensity
above which a good focus can not be obtained. So to get
the best writing rate during single sweep work, first be sure
that the intensity is within the range permitting small spot
size and good focus.
2-9