be unstable. External triggering provides the same result as
CH
1
ONLY
triggering.
Two
signals which
are
time-related can be displayed
in
the chopped mode showing true time relationship.
If
the
signals are not time-related, the Channel 2 display
will
appear
unstable.
Two
single-shot, transient, or random
signals which occur within the time interval determined
by
the
TIME/DIV
switch
(10
times sweep rate) can be compared
using
the CHOP mode.
To
correctly trigger the sweep for
maximum resolution, the Channel 1 signal
must
precede the
Channel 2 signal. Since the signals show true time relation-
ship, time-difference measurements can be made.
Channel 1 Output and Cascaded Operation
If
a lower de·flection factor than provided
by
the
VOL
TS/
DIV
switches
is
desired, Channel 1 can be used as a wide-
band preamplifier for Channel
2.
Apply the input signal to
the Channel 1
INPUT
connector. Connect a 50-ohm
BNC
cable
(18-inch
or shorter cable· for maximum cascaded
fre-
quency response) between the
CH
1
OUT
(side
panel) and
the Channel 2
INPUT
connedors. Set the
MODE
switch to
CH
2 and the
TRIGGER
switch
to
NORM.
With both
VOL
TS/
DIV
switches set to 5
mV,
the deflection factor
will
be
less
than one millivolt/division.
To
provide calibrated one millivolt/division deflection
factor, connect the
.1
volt Calibrator signal to the Channel 1
INPUT
connector. Set the
CH
1
VOLTS/DIV
switch to
.1
and the
CH
2
VOLTS/DIV
switch to 5
mV.
Adjust the Chan-
nel
2
VARIABLE
VOLTS/DIV
control to produce a display
exactly
five
divisions
in
amplitude.
The
cascaded deflection
factor
is
determined by dividing the
CH
1
VOLTS/DIV
switch
setting by 5
(CH
2
VOLTS/DIV
switch and
VARIABLE
control
remain as set above).
For
example,
with
the
CH
1
VOLTS/
DIV
switch set to 5
mV
the calibrated deflection factor
will
be 1 millivolt/ division;
CH
1
VOLTS/DIV
switch set to
10
mV,
2 millivolts/ division, etc.
The
following operating considerations and basic appli-
cations may suggest other
uses
for
this
feature.
1.
If
AC
coupling
is
desired, set the Channel 1 Input
Coupling switch to
AC
and leave the Channel 2 Input
Coupling switch set to
DC.
When both Input Coupling
switches are set to
DC,
DC
signal coupling
is
provided.
2.
Keep both vertical
POSITION
controls set near
mid-
range. If the input signal has a
DC
level
which ne·cessitates
one of the
POSITION
controls being turned
away
from
midrange, correct operation can be obtained by keeping
the Channel 2
POSITION
control near midrange and
using
the Channel 1
POSITION
control to position the trace near
the desired location.
Then,
use
the Channel 2
POSITION
control for exact positioning.
This
method
will
keep both
Input Preamps operating
in
their linear range.
3.
The
output voltage
at
the
CH
1
OUT
connector
is
at
least
25
millivolts/division of
CRT
display
in
all
CH
1
VOLTS/
DIV
switch positions.
4.
The
MODE
switch and Channel 1
VARIABLE
VOLTS/
DIV
control have
no
effect
on
the signal available
at
the
CH
1
OUT
connector.
5.
The
Channel 1 Input Preamp can be
used
as an imped-
ance matching stage
with
or without voltage gain.
The
®
Operating Instructions-Type
453/R453
input resistance
is
one megohm and the output resistance
is
about
50
ohms.
6.
The
dynamic range of the Channel 1 Input Preamp
is
equal to about
20
times the
CH
1
VOLTS/DIV
setting.
The
CH
1
OUT
signal
is
nominally
at
0 volt
DC
for a 0 volt
DC
input
level
(Channel 1
POSITION
control centered).
The
Chanel 1 POSITION control can be used to center the out-
put signal within the dynamic range of the amplifier.
7.
If dual-trace operation
is
used, the signal applied to
the Channel 1
INPUT
connector
is
displayed when Channel
1
is
turned on. When Channel 2
is
turned on, the amplified
signal
is
displayed.
Thus,
Channel 1 trace can be used to
monitor the input signal while the amplified signal
is
dis-
played by Channel
2.
8.
In
special applications where the flat frequency
re-
sponse of the Type
453
is
not desired, a filter inserted
between the
CH
1
OUT
and Channel 2
INPUT
connector
allows the oscilloscope to essentially take on the frequency
response of the filter. Combined
with
method
7,
the·
input can
be monitored by Channel 1 and the filtered signal displayed
by Channel
2.
9.
By
using
Channel 1 as a
SX
low-level voltage pre-
amplifier
(5
mV
position), the Channel 1 signal available
at
the
CH
1
OUT
connector can be used for any application
where a low-impedance preamplified signal
is
needed.
Remember that
if
a 50-ohm load impedance
is
used, the
signal amplitude
will
be about one-half.
Algebraic Addition
General.
The
ADD
position of the
MODE
switch can be
used to display the
sum
or difference of two signals, for
common-mode rejection to remove an undesired signal or for
DC
offset (applying a
DC
voltage
to
one channel to offset
the
DC
component of a signal
on
the other channel).
The
common-mode rejection ratio of the Type
453
is
greater than
20:1
at
20
megahertz for signal amplitudes
up
to eight times the
VOLTS/DIV
switch setting. Rejection ratios
of
100:
1 can typically be achieved between
DC
and 5 mega-
hertz by careful adjustment of the gain of either channel
while observing the displayed common-mode signal.
Deflection Factor. The overall deflection
in
the
ADD
position of the
MODE
switch when both
VOLTS/DIV
switches
are set to the same position
is
the same as the deflection
factor indicated by either
VOLTS/DIV
switch.
The
ampli-
tude of an
added
mode display can be determined directly
from
the resultant
CRT
deflection multiplied by the deflec-
tion factor indicated by either
VOLTS/DIV
switch.
How-
ever,
if
the
CH
1 and
CH
2
VOLTS/DIV
switches are set to
different deflection factors, resultant voltage
is
difficult to
determine
from
the
CRT
display.
In
this
case, the voltage
amplitude of the resultant display can be determined accu-
rately only
if
the amplitude of the signal applied to either
channel
is
known.
Precautions.
The
following general precautions should
be observed when
using
the
ADD
mode.
1.
Do
not exceed the input voltage rating of the Type
453.
2-13
To Next Page
Loading...
Need help?
General
