Tektronix 2221 - Page 38

1
Controls , Connectors , and Indicators - 2221 Operators
22
the SEC / DIV setting
( see Table
3-3 ) . The random
time delay from the trigger to the following sam
ple is measured and used to place the acquired
waveform samples in the correct display memory
location . Any display location is equally likely to
be filled . Table 3-3 gives the statistically expected
number of trigger events required to completely
fill the
display
, assuming
a
uniform
distribution
of
trigger
events
relative to the
sample
interval . The
default
Acquisition
mode
is
Average
.
POSITION
20
SEC /
DIV
ISTORE UNCAL 4 X SEC / DIV
DISPLAY COMPRESS )
19
FAST
RECORD ( 5 us / div to
10 us / div )
updates a
full record of the acquired waveform . The default
Acquisition mode is Sample .
,
ms
us
217.5
50
201
10 5
MW
10
5
20
50
SLOW
RECORD
( 20 us /
div to 50 ms /
div )
updates
a full record of the acquired waveform . The
default Acquisition mode is Peak Detect .
18
1
2.05.10
2
sec
5
STORE
ONLY
AEPETITIVE
STORE
SCAN ( for NORM TRIGGER mode and 0.1 s / div
to 5 s /
div or
EXT
CLOCK )
updates
pretrigger
data when a trigger is received . The waveform
display then scans to the right from the trigger
point to finish the post - trigger acquisition and
then freezes . The default Acquisition mode is
Peak Detect .
21
بال
6530-33
ROLL ( for P - P AUTO TRIGGER mode and 0.1
s / div to 5 s / divor EXT CLOCK ) continuously
acquires and displays signals . Triggers are dis
abled except in SGL SWP . The waveform display
scrolls from right to left across the crt with the
latest samples appearing at the right edge of the
crt . The defauit Acquisition mode is Peak Detect .
Figure 3-3 . Horizontal controls .
3-2 for each " SEC / DIV Setting " is the default mode .
The other
Acquisition
Modes listed for that
setting
may be selected using the ACQUISITION MODE
button .
Waveforms
of
SCAN
and
ROLL
displays
are
updated one data point at a time . All data points of
a
RECORD display are
updated at the same
time
(
total
record
replacement
) .
TRIGGERED ROLL ( for SGL SWEEP TRIGGER
mode and 0.1 s / div to 5 s / div ) -in Triggered Roll ,
the display roils from right to left until the trigger
is received .
Then , the
display
continues rolling
until the posttrigger acquisition record is filled ,
and then the display freezes . The default Acquisi
tion mode is Peak Detect .
1 !
Acquisition
Modes
Storage
Modes
PEAK
DETECT digitizes and
stores
, in
acquisition
memory as
a data
pair , the
minimum
and
max
imum levels of the input signal within the time
represented by 1/50 of a division UN MAG ( 1/25
of a
division
in
CHOP or
ALT ) .
REPETITIVE ( 2 us
/ div to
0.05 us / div
)
requires a
repetitive trigger signal . Sampling of the input sig
nal occurs at the maximum A / D conversion rate .
If a
control
affecting an
acquisition
parameter or
function
is
changed
,
the
acquisition is
reset , and
the waveform being acquired is cleared on the
next
sample
acquired
. On
each valid
trigger , ten
or more equally spaced samples are acquired and
displayed
on
the
waveform record ,
depending on
SAMPLE
samples
the
signal at a
rate
that pro
duces 100 samples per graticule division . In
RECORD
Sampling
modes
,
the
displayed
sample
points are
displayed by vectors
or dots .
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3-6