Chapter 4 Analog Input
© National Instruments Corporation 4-5 M Series User Manual
Analog Input Ground-Reference Settings
M Series devices support the analog input ground-reference settings shown
in Table 4-4.
The AI ground-reference setting determines how you should connect your
AI signals to the M Series device. Refer to the Connecting Analog Input
Signals section for more information.
Ground-reference settings are programmed on a per-channel basis. For
example, you might configure the device to scan 12 channels—four
differentially-configured channels and eight single-ended channels.
M Series devices implement the different analog input ground-reference
settings by routing different signals to the NI-PGIA. The NI-PGIA is a
differential amplifier. That is, the NI-PGIA amplifies (or attenuates) the
difference in voltage between its two inputs. The NI-PGIA drives the ADC
with this amplified voltage. The amount of amplification (the gain), is
determined by the analog input range, as shown in Figure 4-2.
Table 4-4. Analog Input Ground-Reference Settings
AI Ground-Reference
Settings
Description
DIFF In differential (DIFF) mode, the M Series device measures the
difference in voltage between two AI signals.
RSE In referenced single-ended (RSE) mode, the M Series device measures
the voltage of an AI signal relative to AI GND.
NRSE In non-referenced single-ended (NRSE) mode, the M Series device
measures the voltage of an AI signal relative to one of the AI SENSE or
AI SENSE 2 inputs.
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