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Model
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80A
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:
DVM PLUG -IN
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RANGING AND SIGNAL
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CONDITIONING
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r--
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---- --------,
:
MAIN
FRAME
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SAMPLE·AND ·HDLD
A/0
CONVERSION
DATA
STORAGE
ISO
LA TEO BCD
OUTPUT
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111BOA·8-
2540
BCD
Figure 3-15. Sample-and-Hold Circuit Position.
Sample-and-Hold
is located
just
after
the
ranging and signal
conditioning and greatly improves the ability of the 3480 to digitize
a changing input signal.
3-28.
Table 3-8· shows how sample-and-hold improves
digit~ation
accuracy for the
10
V range on
the 3482A
or
3484A
plug-ins. The improvement amounts to a factor of
400. Table 3-9 shows the maximum volts/s and frequency
for various accuracies
and
for any of
the
de ranges on
the
3481 A,
3482A,
or
3484A
plug-ins.
Section III
Figure 3-16. Sample-and-Hold Technique.
Sample-and-hold allows the A/D converter
in
the 3480 to
see
a de
level which
represents
the input voltage at one instant in time. This
results
in
a great
improvement
in the ability
to
accurately digitize an
input signal.
Table
3-8.
Improvement in A/D Conversion
Accuracy Using Sample-and-Hold.
(3482A or 3484A 10 V Range Only)
Accuracy
Maximum V/s
Maximum Sine Wave
Freq
.
at 0 Crossing
Without Sample-and-Hold
±
0.01%
1
V/s
0.018 Hz
With Sample-and-Hold
±
0.Q1%
400
Vis
4.1
Hz
±
0 .1%
4000 V/s
41 Hz
±
1%
40,000 V/s
410
Hz
3-29. DATA STORAGE USED IN THE 2070A.
3-30.
Data Storage
is easiest to
use
when
installed
in a
2070A
Data Logger:
a.
The
2070A contains
both the DVM
and
the
printer
in
one
fan
cooled
package.
Table 3-9. Sample-and-Hold Accuracy.
(Digitization rate is limited to 1 kHz)
3481A
3482A or 3484A
Accuracy
10
v
100 mV
1000 mV
10
v
100
v
1000
v
± 0.01
%
10,000
Vis
1
.5
Vis
40
Vis
400 V
Is
500 V/s
5000 V/s
(100 Hz)
(1 .5 Hz)
(4.1 Hz)
(4 .1 Hz)
(100 Hz)
(100 Hz)
± 0.1
%
100,000
Vis
15
Vis
400
Vis
4000
Vis
5000 V/s
50,000 V/s
(1 kHz)
(15
Hz)
(41 Hz)
(41 Hz)
(250 Hz)
(250 Hz)
± 1%
106
Vis
150
Vis
4000
Vis
40,000
Vis
50,000 V/s
500,000 V/s
(10 kHz)
(150 Hz)
(410Hz)
(410Hz)
(800 kHz)
(800 kHz)
3-9
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