Chapter 2
Configuration and Installation
© National Instruments Corporation
2-29
AT-MIO-16D User Manual
With this type of connection, the instrumentation amplifier rejects both the common-mode noise in
the signal and the ground potential difference between the signal source and the AT-MIO-16D
ground (shown as V
cm
in Figure 2-27).
Differential Connections for Floating Signal Sources
Figure 2-28 shows how to connect a floating signal source to an AT-MIO-16D board configured
for DIFF input. Configuration instructions are included under the Analog Input Configuration
section earlier in this chapter.
+
-
+
Floating
Signal
Source
Input Multiplexers
Instrumentation
Amplifier
V
m
Measured
Voltage
-
V
S
-
+
I/O Connector
AT-MIO-16 Board in DIFF Configuration
3
5
7
17
4
6
8
18
AI GND
1-2
100 k
Ω
Bias
Current
Return
Paths
ACH<8..15>
ACH<0..7>
19
AI SENSE
Figure 2-28. Differential Input Connections for Floating Sources
The 100-k
Ω
resistors shown in Figure 2-28 create a return path to ground for the bias currents of
the instrumentation amplifier. If a return path is not provided, the instrumentation amplifier bias
currents charge up stray capacitances, resulting in uncontrollable drift and possible saturation in the
amplifier. Typically, values from 10 k
Ω
to 100 k
Ω
are used.
Summary of Contents for AT-MIO-16D
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