National Instruments NI 6232 - Manual (Page 45)

Chapter 4 Analog Input
NI 6232/6233 User Manual 4-18 ni.com
Figure 4-6. Single-Ended Connections for Floating Signal Sources (RSE
Configuration)
Refer to the NI 6232/6233 Specifications for the usable range of V
cm
.
Common-Mode Signal Rejection Considerations
For signal sources that are already referenced to some ground point with
respect to the device, the PGIA can reject any voltage caused by ground
potential differences between the signal source and the device. In addition,
with DIFF input connections, the PGIA can reject common-mode noise
pickup in the leads connecting the signal sources to the device. The PGIA
can reject common-mode signals as long as AI x (input signal) is within
±11 V of AI GND.
Field Wiring Considerations
Environmental noise can seriously affect the measurement accuracy of the
device if you do not take proper care when running signal wires between
signal sources and the device. The following recommendations apply
mainly to AI signal routing to the device, although they also apply to signal
routing in general.
Minimize noise pickup and maximize measurement accuracy by taking the
following precautions:
• Use DIFF AI connections to reject common-mode noise.
Selected Channel in RSE or NRSE Configuration
PGIA
Input Multiplexers
–
+
–
Floating or
Grounded
Signal
Source
I/O Connector
AI GND
AI <0.. n>
+
Programmable Gain
Instrumentation
Amplifier
Measured
Voltage
–
+
Digital
Isolators
Isolation
Barrier
V
cm
V
s
V
m