Operating instructions

EXTERNAL . The EXT position connects the signal
from
the EXT TRIG IN connector to
the trigger circuit . The ex-
ternal signal must be time-related to
the displayed wave-
form 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 con-
tains 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 am-
plitude, time
relationship, or waveshape changes of signals
at various points in the circuit to be examined without re-
setting
the TRIGGERING controls .
The=10 push button 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 or . the
positive-going portion of the waveform (see Figure 1-3) .
When several cycles of a signal appear in the display, the
setting of the SLOPE switch is often unimportant .
How-
ever, if only a certain portion of a cycle is to be displayed,
correct setting of the SLOPE switch is important to
provide
a display that starts on the desired slope of the input signal .
Trigger Level
The TRIGGERINGLEVEL 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 sig-
nal . When the
LEVEL
control is
set in the - region, the
trigger
circuit responds
at
a more negative point on the
trigger signal
. Figure 1-3 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 clock-
wise 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
Time Measurement
Operating Instructions-71380
sequence .
The VARIABLE TIME/DIV control must 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 appro-
priate sweep rate .
The VARIABLE TIME/DIV control includes a two-position
switch to determine if the
sweep
rate is
calibrated, or un-
calibrated
. 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 in the
VARIABLE con-
trol . This
feature
is particularly
useful when a specific un-
calibrated sweep rate has been obtained and it is desired to
switch between calibrated and uncalibrated displays .
When making time measurements from the graticule,
the
area between the second
and tenth vertical lines of the gra-
ticule provides the most linear time measurements (see
Figure
1-4)
. 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 .
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
Figure
1-5) .
The
equivalent
length of the magnified sweep is
more than 100 divisions ;
any
10
division portion can be
viewed by adjusting the
POSITION and FINEPOSITION
controls to
bring the desired portion into the viewing area .
When the MAG switch is set to X10 (OUT) the equivalent
magnified sweep rate can be determined by dividing the
TIME/DIV setting by 10 ; the equivalent magnified sweep
rate is displayed on the crt readout .
Variable Hold Off
The HOLD OFF
control
improves
triggering
stability on re-
petitive complex waveforms by effectively changing the
repetition rate of the horizontal sweep signal . The
HOLD
OFF control should normally be set to its
minimum setting .
When a stable display cannot be obtained with
the TRIG-
GERING
LEVEL
control, the HOLD
OFF
control
can be
varied for an improved display . If a stable
display cannot be
obtained at
any setting of the LEVEL and HOLD OFF con-
trols, check the TRIGGERINGCOUPLING and SOURCE
switch
settings .