Tektronix 551 Dual Beam Instruction Manual page 8

V :
To help you get acquainted with your Type 551, we have
outlined in this section some of the more frequently en­
countered oscilloscope applications.
The oscilloscope provides us with the means of actually
looking at waveforms we are interested in. To accomplish
this, we feed the waveforms into the input connectors on the
oscilloscope so that the display on the screen shows how the
voltage of the waveforms changes with time.
The following instructions illustrate the use of the Type
551 in conjunction with the two Type A Plug-In Preamplifiers.
The square-wave calibrator of the oscilloscope is used for
the vertical signal in this demonstration.
Initial Control Settings
Insert the Type A Plug-In Units into the UPPER BEAM and
LOWER BEAM plug-in receptacles in the front panel of the
oscilloscope.
Set the front-panel controls as follows:
Type 551:
FOCUS
INTENSITY
ASTIGMATISM
SCALE ILLUM.
TIME/CM (black)
VARIABLE (red)
HORIZONTAL DISPLAY
(black)
SINGLE SWEEP
(red)
STABILITY
TRIGGERING LEVEL
TRIGGERING MODE
TRIGGER SLOPE
HORIZONTAL POSITION
VERNIER
(red knob)
SQUARE-WAVE CALIBRATOR
(black)
SQUARE-WAVE CALIBRATOR
(red)
POWER
( A ) ®
centered
full left
(counterclockwise)
centered
centered
.5 MILLISEC
CALIBRATED
NORMAL
OUT
PRESET
full left or
full right
AUTO.
+.UPPER
centered
centered
10
VOLTS
ON
G E T T I N G
A C Q U A I N T E D
Type A (both units):
INPUT SELECTOR
VOLTS/CM
VARIABLE
VERTICAL POSITION
Turn the INTENSITY control to the right until a horizontal
trace of useful brightness appears on the screen. Adjust the
FOCUS and ASTIGMATISM controls for the sharpest trace.
Connect a pair of leads from the CAL. OUT connector to the
INPUT A connectors of both plug-ins. The display on the
screen should now be two square waves, positioned one
above the other. Slightly readjust the ASTIGMATISM, FOCUS/
and INTENSITY controls so that the display has the best
sharpness and suitable brightness as shown in Fig. 3-1. Cen­
ter the display on the graticule, each square-wave about its
own center line, by means of the VERTICAL- and HORIZON­
TAL-POSITION controls.
Triggering in the Automatic Mode
The SQUARE-WAVE CALIBRATOR waveform you have
been looking at is a periodic signal— that is, recurs at reg­
ular intervals. We got a stable (stationary) display of this
waveform by setting the oscilloscope controls so that each
horizontal sweep of the spot across the screen started at a
given point on the waveform. These settings were given in
the table above. For present purposes then, the starting of
each horizontal sweep across the screen can be called 'trig­
gering'' the sweep. As in the procedure above, this can be
accomplished with a minimum of adjustment by setting the
red TRIGGERING MODE knob in the AUTO, position. That
is, we used the AUTO, mode of triggering.
Because of its simplicity of operation, the AUTO, mode is
one of the most useful triggering modes. In particular, you
don't have to adjust the TRIGGERING LEVEL or STABILITY
controls when you use the AUTO. mode. Uses of these con­
trols are described later in this manual.
EFFECTS OF THE TYPE A PLUG-IN CONTROLS
Effect of the Input Selector Switch
Turn the INPUT SELECTOR switch of the UPPER BEAM plug­
in unit to INPUT A, DC. Notice the vertical shift in the
position of the trace. This is due to the fact that the output
INPUT A, AC
5
CALIBRATED
centered
2-1