National Instruments SCXI-1126, Руководство пользователя

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Chapter 2 Using the SCXI-1126
© National Instruments Corporation 2-3 SCXI-1126 User Manual
Figure 2-3. Floating AC Coupled Signal Connection for the SCXI-1126
Caution Adding the bias resistor (R
bias
), shown in Figure 2-3, breaks the isolation barrier.
Figure 2-4. AC Coupled Signal Connection for the SCXI-1126 with
High Common-Mode Voltage
When you connect AC coupled signals to the SCXI-1126, as shown in
Figures 2-3 and 2-4, connect an external resistor from the positive input
channel to the signal reference to provide the DC path for the positive input
bias current. Typical resistor values range from 100 k
Ω
to 1 M
Ω.
This
solution, although necessary in this case, reduces the input impedance of
the input channel. This can introduce loading errors if the signal source has
a high output impedance. Refer to Appendix A,
Specifications , for
information on channel input impedance.
+
–
+
F – V
CH–
CH+
Analog
Ground
Isolated
Ground
SCXI-1126 Module SCXI Terminal Block Sensor
F
s
V
out
R
bias
CHSGND
Optional
R
shunt
+
–
+
F – V
+
–
CH–
CH+
Analog
Ground
Isolated
Ground
SCXI-1126 Module SCXI Terminal Block Sensor
High
CMV
V
cm
F
s
V
out