Tektronix 2221 - Page 37

Controls
,
Connectors
,
and
Indicators - 2221
Operators
o
CH 2 -
Selects
only the
Channel
2
input
signal for
acquisition or
display
.
16 )
Vertical
POSITION
Controls -
Control the
vertical
display position of the CH 1 and CH 2 signals .
ADD - Displays or acquires the sum of Channel 1
and Channel 2 input signals when BOTH is also
selected . The difference of the Channel 1 and
Channel 2
inputs
signals
is
displayed and
acquired when the Channel 2 signal is inverted .
Л
П
П
П
Л
П
П
Л
П
ALT
-
Alternately
displays
the
NON -
STORE
Channel 1 and
Channel 2
input
signals
.
The
NON
-
STORE
alternation
occurs
during
retrace at
the end of each sweep . ALT Vertical MODE is
most useful for acquiring and viewing both chan
nel input signals at sweep rates of 0.5 ms per
division and faster . Channel 1 and Channel 2
STORE mode signals are acquired on alternate
acquisition cycles at one - half the sampling rate of
a single - channel acquisition .
IN
STORE mode , the
controls
determine the
verti
cal
position
of displayed waveforms
during
acquisition and in SAVE mode . The STORE mode
waveforms may also
be
vertically
repositioned
during
the
time
between
acquisitions . Any
por
tions of a signal being acquired that are outside
the dynamic range of the A / D converter are
blanked when positioned on screen . The Vertical
POSITION
controls
can
also
reposition a
vertically
expanded SAVE waveform so that portions of the
waveform
outside the
graticule
area can
be
observed .
In NON - STORE X - Y mode , the CH 2 POSITION
control
vertically
positions the
display , the
hor
izontal
POSITION
control
positions
the
display
horizontally , and the CH 1 POSITION control is
not active . In STORE mode , the CH 1 POSITION
control is active , and both it and the Horizontal
POSITION
control affect the
horizontal
position of
the displayed waveform .
CHOP - Switches
the
NON -
STORE
display
between
Channel
1
and
Channel 2
vertical
input
signals during the sweep . The chopped switching
rate for
NON -
STORE
mode
(
CHOP
frequency ) is
approximately 500 kHz . Chopped STORE mode
signals are acquired on alternate time - base clock
cycles with
each
channel
being
acquired
at
one
half the
sampling rate of a
single
-
channel
acquisi
tion
.
In
STORE
mode
at
sweep
speeds of
5 us
per division to 0.05 us per division , CHOP
becomes ALT
mode
.
17 )
GND
Connector -
Provides
an
auxiliary
ground
con
nection directly to the instrument chassis via a
banana - tip
jack
.
C
HORIZONTAL
See Figure
3-3 for the
location
of
items 18
through
22 .
BW LIMIT
Switch - In NON
-
STORE
mode
, limits
the
bandwidth of the
vertical
amplifier
system and
the Trigger system to approximately 10 MHz
when pressed in . This reduces interference from
unwanted high - frequency signals when viewing
low -
frequency signals . In
STORE mode ,
pressing
in the
BW
LIMIT
switch
reduces
only the
trigger
system bandwidth . Press a second time to
release the switch and regain fuil bandwidth .
18 SEC / DIV
Switch -
Determines
the SEC
/ DIV setting
for the NON - STORE sweeps and the STORE mode
time base for acquiring and displaying waveforms .
In NON - STORE , the SEC / DIV switch selects cali
brated sweep rates from 0.5 s to 0.05 us per division
in a 1-2-5
sequence of 22 steps
.
П
Л
П
П
1
Л
П
П
n П
X - Y Switch - Automatically selects the X - Y mode
when pressed in
. The CH 1
input signal
provides
horizontal
deflection for X - Y
displays
,
and the
CH 2 input signal provides vertical deflection . The
STORE mode X - Y
sampling
rate
is
controlled by
the SEC / DIV switch . The X - Y waveform is nor
nally
acquired
in
SAMPLING mode and
displayed
with dots . In
STORE mode at SEC /
DIV switch
settings of 5 s per division to 10 us per division ,
the CH 1 and
CH 2 signals
are
acquired
in
a
chopped manner with no more than 100 ns
between
corresponding
sample
points on
oppo
site
channels at
the
maximum
sampling rate of
10 MHz
per
channel
.
The CH 1
signal
is
sampled
before
the
CH
2
signal .
In STORE mode , the SEC / DIV switch determines the
acquisition and display modes , sets the sampling
rate , and establishes the time scale factor of the
displayed waveforms . The SEC / DIV parameters
displayed on the crt readout are for the waveforms
identified by CURSORS .
Table 3-2 lists
the
Storage
,
Acquisition
and
Display
modes
with
respect
to
the SEC / DIV
switch
setting
and the
selected
Trigger
mode . The "
Acquisition
Mode " shown in bold face and listed first in Table
o
3-5