Chapter 4 Analog Input
X Series User Manual 4-4 ni.com
Working Voltage Range
On most MIO X Series devices, the PGIA operates normally by amplifying
signals of interest while rejecting common-mode signals under the
following three conditions:
• The common-mode voltage (V
cm
), which is equivalent to subtracting
AI <0..x> GND from AI <0..x>–, must be less than ±10 V. This V
cm
is
a constant for all range selections.
• The signal voltage (V
s
), which is equivalent to subtracting AI <0..x>+
from AI <0..x>–, must be less than or equal to the range selection of
the given channel. If V
s
is greater than the range selected, the signal
clips and information are lost.
• The total working voltage of the positive input, which is equivalent to
(V
cm
+ V
s
), or subtracting AI GND from AI <0..x>+, must be less than
±11 V.
If any of these conditions are exceeded, the input voltage is clamped until
the fault condition is removed.
Analog Input Ground-Reference Settings
MIO X Series devices support the following analog input ground-reference
settings:
• Differential mode—In DIFF mode, the MIO X Series device
measures the difference in voltage between two AI signals.
• Referenced single-ended mode—In RSE mode, the MIO X Series
device measures the voltage of an AI signal relative to AI GND.
• Non-referenced single-ended mode—In NRSE mode, the MIO
X Series device measures the voltage of an AI signal relative to one of
the AI SENSE or AI SENSE 2 inputs.
The AI ground-reference setting determines how you should connect your
AI signals to the MIO X 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.
MIO X 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
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