參數(shù)資料
型號(hào)： SDM863A
英文描述： 16 Single Ended/8 Differential Input 12-BIT DATA ACQUISITION SYSTEMS
中文描述： 16單端/ 8差分輸入12位數(shù)據(jù)采集系統(tǒng)
文件頁數(shù)： 8/27頁
文件大小： 256K
代理商： SDM863A
SDM862/863/872/873
8
All data acquisition systems using a MUX require consider-
ation of the errors that may be introduced by MUX output
capacitance. The applications information explains this more
fully in the input filtering section.
Shown in Figure 3 is an application that demonstrates the
flexibility of signal conditioning and gives the opportunity
to use a higher bandwidth filter. Diodes shown are low
leakage types (1na). The low output impedance of the
amplifiers reduces the time taken to charge MUX capaci-
tance C
M
.
INSTRUMENT AMPLIFIER
The instrument amplifier (INA) presents a very high input
impedance to the signal source, eliminating gain errors
introduced by voltage divider action between the source
output impedance and SDM input impedance. Where the
differential models are used, the INA performs the differen-
tial to single-ended conversion required to drive the sample/
hold amplifier. Gains may be set by using external jumpers,
to values of 1 (no jumper), 10 and 100. For gains other than
these presets, the following formula may be used to find an
external resistor value to add in series with the G = 10 or G
= 100 jumpers.
40k
Where Ri = 4444
, G = 10 input.
G – 1
It should be noted that the internal gain set resistors have a
±
20% tolerance and
±
20ppm/
°
C drift.
404
, G = 100 input.
to ensure that neither of the differential inputs exceed the
maximum input range. Otherwise, signal distortion will
result. A return path for the input bias currents must always
be provided. This prevents the charging of stray capaci-
tances in applications using floating sources, such as trans-
formers and thermocouples. Multiplexer inputs are protected
from overvoltage, as indicated in the electrical specifica-
tions, and should be current limited to 20mA.
Where high-speed operation is required and channels require
rapid sampling, then it is important to buffer the inputs
against the effect of current sharing between the MUX
output capacitance and the input filter capacitance. See
Figure 2.
SYSTEM DESCRIPTION
The SDM comprises four circuit elements—an input-pro-
tected multiplexer, an instrumentation amplifier, a sample/
hold amplifier, and an analog-to-digital converter.
INSTALLATION
MULTIPLEXER
The SDM family has a choice of input multiplexers (MUX).
SDM862 and SDM872:
16 single-ended inputs
SDM863 and SDM873:
8 differential inputs
On all models, the analog inputs may be expanded using the
enable control. See Figure 1. When the enable is at a logic
“0,” the internal MUX is disabled, allowing additional
multiplexers to be connected in parallel. The limiting factor
for the number of additional multiplexers is the cumulative
effect of leakage current flowing in the signal source imped-
ance, causing offset errors.
Differential inputs will generally eliminate the noise associ-
ated with common system grounds, but care must be taken
FIGURE 1. External Multiplexer Connections for Differen-
tial and Single-Ended Operation.
FIGURE 2. Filter and MUX Capacitance
.
– Ri
R
ext
=
C
f
C
M
C
f
MUX
A3
A2
A0
Out
A3
A2
A0
Out
A2
A1
A0
– Out
+Out
D
E
D
E
D
E
49 50 51 52 48 65
66
53
SDM8X2
66
A2
A1
A0
–Out
D
E
A0
A1
A2
A3
A4
MUX
Extern
49 50 51 48
65
53
SDM8X3
67
A0
A1
A2
A3
INA
INA
MUX
Intern
MUX
Intern
MUX
Extern
相關(guān)PDF資料
PDF描述
SDM863B 16 Single Ended/8 Differential Input 12-BIT DATA ACQUISITION SYSTEMS
SDM863J 16 Single Ended/8 Differential Input 12-BIT DATA ACQUISITION SYSTEMS
SDM863K 16 Single Ended/8 Differential Input 12-BIT DATA ACQUISITION SYSTEMS
SDM872R 16 Single Ended/8 Differential Input 12-BIT DATA ACQUISITION SYSTEMS
SDM872S 16 Single Ended/8 Differential Input 12-BIT DATA ACQUISITION SYSTEMS
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
SDM863B 制造商:BB 制造商全稱:BB 功能描述:16 Single Ended/8 Differential Input 12-BIT DATA ACQUISITION SYSTEMS
SDM863J 制造商:BB 制造商全稱:BB 功能描述:16 Single Ended/8 Differential Input 12-BIT DATA ACQUISITION SYSTEMS
SDM863K 制造商:BB 制造商全稱:BB 功能描述:16 Single Ended/8 Differential Input 12-BIT DATA ACQUISITION SYSTEMS
SDM863R 制造商:BB 制造商全稱:BB 功能描述:16 Single Ended/8 Differential Input 12-BIT DATA ACQUISITION SYSTEMS
SDM863S 制造商:BB 制造商全稱:BB 功能描述:16 Single Ended/8 Differential Input 12-BIT DATA ACQUISITION SYSTEMS
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