Tektronix 535A, Instruction Manual

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Operating Instructions —Type 535A
determine the sweep speed and the horizontal size of the
displayed waveform. The controls are set to display the
portion of the waveform you wish to observe.
Time Base A has 24 accurately calibrated sweep rates
ranging from .1 microseconds to 5 seconds per centimeter.
These calibrated sweep rates are obtained only when the
VARIABLE TIME/CM control is in the fully clockwise posi­
tion. The VARIABLE TIME/CM control permits you to vary
the sweep rates continuously between .1 microseconds and
approximately 12 seconds per centimeter. All sweep rates
obtained with the VARIABLE TIME/CM control in any
position but fully clockwise are uncalibrated. Uncalibrated
sweep rates are indicated when the UNCALIBRATED lamp
is lit.
Time Base B has sweep rates ranging from 2 microseconds
to 1 second per centimeter in 18 steps. There is no VARI­
ABLE TIME/CM control for Time Base B. The red LENGTH
control adjusts the sweep length between approximately 4
and 10 centimeters.
Sweep Triggering
The oscilloscope display is formed by the repetitive sweep
of the spot across the oscilloscope screen. If the sweeps
are allowed to occur at random or at a rate unrelated to the
rate of occurence of the input waveform, the displayed
waveform will be traced out at a different point on the
screen each time the sweep runs. This will either cause
the waveform to drift arcoss the screen or to be indistin­
guishable.
In most cases it is desirable for a repetitive waveform to
appear stationary on the oscilloscope screen so that the
characteristics of the waveform can be examined in detail.
As a necessary condition for this type of display, the start
of the sweep must bear a definite, fixed-time relationship
to the appearance of the input waveform. This means
that the sweep must be synchronized with the input wave­
form. In the Type 535A Oscilloscope this is accomplished
by starting (triggering) the sweep with the displayed wave­
form or with another waveform bearing a definite time re­
lationship to the displayed waveform.
The following paragraphs outline the means for selecting
the triggering source, triggering slope, and triggering level
with specific information regarding the operation of the con­
trols affecting triggering. Triggering controls for Time Base
A and Time Base B are virtually identical so that the follow­
ing information is applicable to both time-base units. Trig­
gering of the sweep is adjusted by the respective STABILITY,
TRIGGERING LEVEL, TRIGGERING MODE, and TRIGGER
SLOPE controls.
Selecting the Triggering Source
In preparing the Type 535A Oscilloscope for triggered
operation of the sweep, it is first necessary to select the
triggering signal which will provide the best display for the
particular application. The sweep can be triggered by the
displayed waveform, a line-frequency waveform, or by an
externally derived waveform. This selection is made by the
setting of the TRIGGER SLOPE control. Each type of trig­
gering has certain advantages for some applications.
Triggering from the displayed waveform is the method-
most
commonly used. The displayed waveform is selected
when the TRIGGER SLOPE control is in either the +INT. or
2-4