Single-ended connection considerations, Single-ended connection considerations -16 – National Instruments NI 6232 User Manual
Page 43
Chapter 4
Analog Input
4-16
ni.com
Figure 4-5. Differential Connections for Floating Signal Sources
This figure shows AI GND connected to the ground reference point for the
floating signal source. If you do not connect AI GND, the source is not
likely to remain within the common-mode signal range of the PGIA due to
the floating source or the isolation barrier. The PGIA then saturates,
causing erroneous readings.
You must reference the source to AI GND. The easiest way to make this
reference is to connect the positive side of the signal to the positive input of
the PGIA and connect the negative side of the signal to AI GND as well as
to the negative input of the PGIA, without using resistors.
Single-Ended Connection Considerations
A single-ended connection is one in which the device AI signal is
referenced to a ground that it can share with other input signals. The input
M Series Isolated Device Configured in DIFF Mode
PGIA
–
+
–
+
–
+
V
s
Floating
Signal
Source
AI GND
Input Multiplexers
V
m
Instrumentation
Amplifier
AI +
AI –
Measured
Voltage
Digital
Isolators
Isolation
Barrier
I/O Connector