Chapter 4
Analog Input
©
National Instruments Corporation
4-5
Table 4-3 shows how signals are routed to the NI-PGIA.
For differential measurements, AI 0 and AI 8 are the positive and negative
inputs of differential analog input channel 0. For a complete list of signal
pairs that form differential input channels, refer to the
Caution
The maximum input voltages rating of AI signals with respect to AI GND (and
for differential signals with respect to each other) and earth/chassis ground are listed in the
Maximum Working Voltage
section of the
NI 6232/6233 Specifications
. Exceeding the
maximum input voltage or maximum working voltage of AI signals distorts the
measurement results. Exceeding the maximum input voltage or maximum working voltage
rating also can damage the device and the computer. Exceeding the maximum input voltage
can cause injury and harm the user. NI is
not
liable for any damage or injuries resulting
from such signal connections.
AI ground-reference setting is sometimes referred to as
AI terminal
configuration
.
Configuring AI Ground-Reference Settings in
Software
You can program channels on an M Series device to acquire with different
ground references.
To enable multimode scanning in LabVIEW, use
NI-DAQmx Create
Virtual Channel.vi
of the NI-DAQmx API. You must use a new VI for
each channel or group of channels configured in a different input mode. In
Figure 4-3, channel 0 is configured in differential mode, and channel 1 is
configured in RSE mode.
Table 4-3.
Signals Routed to the NI-PGIA
AI Ground-Reference
Settings
Signals Routed to the Positive
Input of the NI-PGIA (V
in+
)
Signals Routed to the Negative
Input of the NI-PGIA (V
in–
)
RSE and NRSE
AI <0..15>
AI GND
DIFF
AI <0..7>
AI <8..15>
