Tektronix 7B10 Instruction Manual page 19

Operating Instructions—
7B10
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
IN
1
MQ/OUT
50
fJ
pushbutton
provides
a
convenient
means
of
selecting external-trigger input
impedance. Pushing
the button
in
sets the amplifier input
impedance
to
1
Mfi and
the
OUT
position provides
50
Q
input
impedance.
HORIZONTAL
SWEEP
RATES
The TIME/DIV
switch provides calibrated
sweep
rates
from
.2
seconds/division
to
2 nanosecond/division
in a
1
-2-5
sequence.
The
VARIABLE TIME/DIV
control
must
be
in
the
calibrated position
and
the
MAG
switch
set to
XI
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
sicwer
position.
A
calibrated
sweep
rate
can be obtained
in
any
position
of
the
VARIABLE
control
by pressing
in
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.
TRIGGERING 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, display starts
on
the
positive-going portion of
the
waveform
(see Figure
2-2).
When
several cycles
of
a signal
appear on
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
important
to
provide
a
display that
starts
on
the desired
slope
of
the input
signal.
TRIGGERING 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 2-2
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.
In
the
HF
SYNC
mode, the
trigger
LEVEL
control varies
the
sensitivity of the Trigger Generator.
The LEVEL
control
is
set to
provide
a stable display.
TIME
MEASUREMENTS
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.
2-3). 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
LINE
TENTH-VERTICAL
LINE
I
TIME
MEASUREMENT,
AREA
C
175?-06
Fig.
2-3.
Area
of graticule used
for
most
accurate time
measurements.
2-7