Tektronix 2246 User Manual

dc SYMBOL
Figure 6-17. Setting a specific Trigger LEVEL.
waveform display will now appear (assuming the A INTEN-
SITY is set to a viewing level), and it will be triggered on
the larger amplitude pulses of the signal.
Once triggering is obtained, the A SEC/DIV setting may
be set to a faster sweep speed to expand the triggering
pulse for making any measurements wanted.
USE OF THE ADD MODE
With the VERTICAL MODE set to ADD, the resulting
waveform is the algebraic sum of the signals applied to the
Channel 1 and Channel 2 inputs (CH 1 + CH 2). A plus
symbol (+) appears in the readout between the CH 1 and
CH
2
VOLTS/DIV
setting
readout
to
indicate
that
ADD
is
active.
If
the
CH
2
INVERT
feature
is
turned
on
(INVERT
button
light
on),
the
waveform
displayed
is
the
difference
between
the
signals
applied
to
the
Channel
1
and
Channel
2
inputs.
Neither
CH
1
nor
CH
2
waveform
needs
to
be
displayed
to
obtain
the
ADD
trace,
but
any
or
ALL.
vertical
input channels may be displayed at the same time if
wanted by the user.
When
the
VOLTS/DIV
switches
of
CH
1
and
CH
2
are
both
set
to
the
same
setting,
the
total
deflection
factor
in
the
ADD
mode
is
equal
to
the
deflection
factor
indicated
by
either
VOLTS/DIV
readout.
The
l-
VOLTS
-I
cursors
may
be
used
to
make
voltage
measurements
on
the
ADD
trace
if
either
CH
1
or
CH
2
is
displayed
along
with
the
ADD
trace
(and,
of
course,
both
CH
1
and
CH
2
at
the
same
VOLTS/DIV
setting).
If
any
voltage
measurement
function
is
active,
turning
off
CH
1
and
CH
2
to
display
the
Measurement Processes and Applications— 2246 Operators
ADD trace by itself causes the message "INVALID
MEASUREMENT SOURCE” to appear, and cancels the
measurement, If calling for a voltage measurement with
ADD displayed and neither CH 1 nor CH 2 displayed, the
CH 1 VERTICAL MODE is turned on, and the measure-
ment is initialized to the signal applied to the CH 1 input.
Two commen uses for ADD mode are: (1) providing a
dc offset to bring an ac signal riding on top: of a large de
voltage within the graticule viewing area and (2) canceling
out a large line-frequency signal component to view some
smali feature riding on the waveform in greater detail using
common-mode rejection.
NOTE
The following general precautions should be
observed when using ADD mode:
1. Do not exceed the input-voltage rating of the
oscilloscope or probe.
2. Do not apply signals that exceed the equivalent
of about eight times the VOLTS/DIV switch settings,
since large voltages may distort the display. For
_ example, with a VOLTS/DIV setting of 0.5 V, the
voltage applied to that channel should not exceed
av.
3. Use CH 1 and CH 2 POSITION control settings
which most nearly position the signal on each chan-
nel to mid-screen, when viewed separately. This
ensures the greatest dynamic range for ADD mode
signal displays.
4. To have similar responses for both channels, use
the same Input COUPLING for both CH 1 and CH 2.
The following procedure shows how to eliminate an
unwanted ac input-power frequency signal component
from the displayed signal.
1.
Set
the
front
panel
controis
to
obtain
a
baseline
trace.
Use
the
settings
given
for
making
a
+PEAK
volt-
age
measurement,
but
do
not
apply
any
signals
and
center
the
baseline
trace
vertically.
2. Apply the signal of interest containing the unwanted
line-frequency component to the CH 1 input connector.
3. Apply a line-frequency signal to the CH 2 input con-
nector.
To
maximize
cancellation,
the
signal
applied
to
the
6-21

Tektronix 2246 Specifications

General

Brand	Tektronix
Model	2246
Category	Test Equipment
Language	English