Tektronix 551 Dual Beam Instruction Manual page 9

Getting Acquainted— Type 551
waveform from the SQUARE-WAVE CALIBRATOR has both
an ac (square wave) component and a dc component. When
the INPUT SELECTOR switch is in the AC position, the effect
of the DC component of the waveform is excluded from the
display. When this switch is in the DC position, the display
indicates both the ac and dc component of the waveform
being viewed. The dc component of the waveform causes
the entire display to rise or fall on the screen.
With the INPUT SELECTOR switch, you can select for dis­
play either a signal fed into the INPUT A connector or a
signal fed into the INPUT B connector. This arrangement is
provided so that you can quickly compare the two wave­
forms.
With no signal source connected to INPUT B, turn the IN­
PUT SELECTOR switch to INPUT B, AC. Since no signal is
now being displayed, only a horizontal reference trace will
appear on the screen. Now remove the SQUARE-WAVE
CALIBRATOR lead from the INPUT A connector and connect
it to INPUT B. The square-wave display should now re­
appear on the screen.
Now return the SQUARE-WAVE CALIBRATOR lead to the
INPUT A connector and reset the INPUT SELECTOR switch
to INPUT A, AC. This again produces the square-wave
display.
Effects of the Volts/Cm Controls
Turn the black VOLTS/CM knob on either plug-in succes­
sively to positions both to the right and left of the 5 position.
Notice that when you set the VOLTS/CM switch to higher-
numbered positions, the amount of vertical deflection pro­
duced on the screen by the SQUARE-WAVE CALIBRATOR
waveform is reduced, and vice versa.
Reset the black VOLTS/CM knob to the 5 position.
Turn the red variable knob to the left. Notice that this
reduces the amount of vertical deflection produced on the
screen by the SQUARE-WAVE CALIBRATOR waveform.
Preset the VARIABLE control to the CALIBRATED position.
The above operations point up the fact that the VOLT/CM
switch (black knob) and the VARIABLE control (red knob) pro­
vide control to the amount of vertical deflection which re­
sults from feeding a waveform having a given peak-to-peak
voltage into the INPUT connector.
Effect of the Vertical Position Control
Turn the VERTICAL POSITION control back ond forth, and
notice that this raises and lowers the display on the screen.
Note especially that if you position the display off the grati­
cule in either direction, one or both of the beam-position
indicator lamps, located above the graticule, will indicate
in which direction the display is positioned off the screen.
This tells you which way to turn the VERTICAL POSITION
control to bring the display back on the screen.
Notice that, as you position the upper beam toward the
bottom of the graticule, the upper beam display disappears
approximately at the center line of the lower beam. Simi­
larly, as you position the lower beam toward the top of the
graticule it disappears at approximately the center line of
the upper beam.
2-2
With the VERTICAL POSITION controls of both the UPPER
BEAM and LOWER BEAM plug-ins, position both displays at
the center of the graticule. You will notice that the square
wave appears to consist of a single display when this is done.
Waveform comparisons may be made easily by using the
center two centimeters of the graticule in this manner.
EFFECT OF THE TYPE 551 OSCILLOSCOPE
CONTROLS
Effect of the Horizontal Position Control
Turn the HORIZONTAL POSITION control back and forth
and notice that the display moves to the left and right of
the screen. Note especially that if you position the knob
to the extreme right, one of the beam position indicators
(located above the graticule) will indicate that the display
is positioned off center towards the right.
Now reset the HORIZONTAL POSITION control to return
the display to the center of the screen.
Effect of the Time/CM Controls
Turn the black TIME/CM knob successively to positions
both to the right and left of the .5 MILLISEC position. Notice
that the display expands or contracts horizontally as the
switch is turned.
Reset the TIME/CM switch to the .5 MILLISEC position.
Rotate the red VARIABLE knob. Notice that as you do so
the display contracts horizontally. Turn the red knob to the
CALIBRATED position and then slightly away from the CALI­
BRATED position. Notice that as soon as the red knob leaves
the CALIBRATED position, the UNCALIBRATED light will
light.
Return the red VARIABLE knob to the CALIBRATED po­
sition.
The above operations point up the fact that the TIME/CM
and VARIABLE controls provide control of the sweep rate,
and thus of the number of cycles of the display which ap­
pear on the screen when a waveform having a fixed repeti­
tion rate is displayed.
Effect of the 5X Magnifier
Turn the HORIZONTAL DISPLAY switch to the 5X MAG.
position. Observe that as you do so, the MAG. ON light
comes on. Turn the HORIZONTAL DISPLAY switch from 5X
MAG. to NORMAL and back several times. Observe that the
portion of the display which occupies the middle two centi­
meters of the graticule is expanded to fill the entire graticule
length when the HORIZONTAL DISPLAY switch is turned to
the 5X MAG. position.
With the HORIZONTAL DISPLAY switch in the 5X MAG.
position, turn the HORIZONTAL POSITION control through
its range and notice that the display has been expanded
throughout its entire length.
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