National Instruments PCI-1200 Manual Do Utilizador
Chapter 3
Signal Connections
© National Instruments Corporation
3-11
Differential Connections for Floating Signal Sources
Figure 3-4 shows how to connect a floating signal source to a PCI-1200
board configured for DIFF input. Configuration instructions are in the
board configured for DIFF input. Configuration instructions are in the
section of Chapter 2,
Figure 3-4. Differential Input Connections for Floating Sources
The 100 k
Ω resistors shown in Figure 3-4 create a return path to ground for
the bias currents of the instrumentation amplifier. If there is no return path,
the instrumentation amplifier bias currents charge stray capacitances,
the instrumentation amplifier bias currents charge stray capacitances,
+
+
Floating
Signal
Source
V
m
Measured
Voltage
V
s
+
I/O Connector
PCI-1200 in DIFF Configuration
1
3
5
7
2
4
6
8
100 k
Ω
Bias
Current
Return
Return
Paths
ACH0
AGND
11
ACH2
ACH4
ACH6
ACH1
ACH3
ACH5
ACH7
100 k
Ω
–
–
–