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LINE. The LINE position connects a sample of the power-
line voltage from
the mainframe
to the trigger circuit.
Line triggering is useful when the input signal is time-
related (multiple or submultiple) to the line frequency.
It
is also
useful
for
providing
a stable
display
of a line
frequency
component
in a complex
waveform.
EXTERNAL.
The EXT position connects the signal from
the
EXT
TRIG
IN connector
to the trigger circuit. The
external
signal
must
be
time-related
to the
displayed
waveform for a stable display. An external trigger signal
can
be
used
to provide
a triggered
display when
the
internal signal
is either too low in amplitude for correct
triggering
or
contains
signal
components
on
which
triggering
is not
desired.
It is also
useful
when
signal
tracing in amplifiers, phase-shift networks, wave-shaping
circuits, etc.
The signal from a single point in the circuit
can be connected to the EXT TRIG IN connector through a
probe or cable. The sweep is then triggered by the same
signal
at
all
times
and
allows
amplitude,
time
relationship, or waveshape
changes of signals at various
points in the circuit to be examined without resetting the
TRIGGERING
controls.
The
= 10 pushbutton
attenuates
the
external
trigger
signal by a factor of 10.
Attenuation of high-amplitude
external
trigger
signals
is desirable
to
increase
the
effective range
of the LEVEL
control
TRIGGER
SLOPE
The
TRIGGERING
SLOPE
switch
(concentric
with
the
TRIGGERING
LEVEL
control)
determines
whether
the
trigger circuit responds on the positive- or negative-going
portion of the trigger signal. When the SLOPE switch is
in the (+) (positive-going) position, the display starts on
the positive-going portion of the waveform
(see Fig.
1-4).
When
several cycles of a signal appear in the display, the
setting
of
the
SLOPE
switch
is
often
unimportant.
However,
if only a certain
portion of a cycle
is to be
displayed,
correct
setting
of
the
SLOPE
switch
is
necessary
to provide a display that starts on the desired
slope
of the
input
signal.
TRIGGER
LEVEL
The
TRIGGERING
LEVEL
control determines
the voltage
level
on
the
trigger
signal
at
which
the
sweep
is
triggered.
When
the LEVEL control is set in the + region,
the trigger circuit
responds
at a more
positive point on
the trigger signal. When the LEVEL control is set in the ~
region,
the
trigger
circuit
responds
at a more
negative
point
on
the
trigger
signal.
Figure
1-4 illustrates this
effect
with different
settings of the SLOPE
switch.
To set the LEVEL
control, first select the TRIGGERING
MODE,
COUPLING,
SOURCE,
and SLOPE.
Then set the
LEVEL
control
fully
counterclockwise
and
rotate
it
clockwise
until the display starts at the desired point
HORIZONTAL
SWEEP
RATES
The
TIME/DIV
switch
provides
calibrated
sweep
rates
from 5 seconds/division to 10 nanoseconds/division in a
1-2-5 sequence. The VARIABLE
TIME/DIV control must
REV A MAR 1981
Operating Instructions—7B87
be in the calibrated position and the MAG
switch set to
X1
to obtain the sweep
rate indicated by the TIME/DIV
switch.
However, the mainframe CRT readout will display
the appropriate sweep rate.
The VARIABLE
TIME/DIV control includes a two-position
switch
to determine
if the sweep
rate is calibrated, or
uncalibrated. When the VARIABLE control is pressed in,
it is inoperative and the sweep rate is calibrated. When
pressed
and
released outward,
the VARIABLE
control is
activated
for uncalibrated
sweep
rates, to at least the
sweep
rate of the next slower
position.
A calibrated sweep rate can be obtained in any position
of
the
VARIABLE
control
by
pressing
the
VARIABLE
control. This feature is particularly useful when a specific
uncalibrated
sweep
rate
has been
obtained
and
it is
desired
to switch
between
calibrated and
uncalibrated
displays.
TIME
MEASUREMENT
When
making time measurements from the graticule, the
area between
the second and tenth vertical lines of the
graticule provides
the most
linear time
measurements
(see Fig. 1-5). Position the start of the timing area to the
second vertical line and adjust the TIME/DIV switch so
the end of the timing area falls between the second and
tenth
vertical
lines.
SECOND-VERTICAL
TENTH-VERTICAL
LINE
LINE
RI
ORIG
OI
RUC Kc Son cca Gace Re
sa eee ee eres aes eee ee eee eee feet
—t{—
—_}—
+
|+——— Time measurement ———>|
AREA
1752-06
Figure
1-5.
Area of graticule used for most
accurate
time
measurements.
SWEEP
MAGNIFICATION
The sweep
magnifier can be used to expand the display
by a factor of 10. The center division of the unmagnified
display is the portion visible on the crt in the magnified
form
(see
Fig.
1-6).
The
equivalent
length
of
the
1-11
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