To connect non-referenced single-ended voltage signals to the PCIe-7856, you must connect
the voltage ground signal to AI SENSE in order to keep the common-mode voltage in the
specified range.
Figure 3. Connecting Non-Referenced Single-Ended Signals to the PCIe-7856
PGIA
ADC
AI+
NI PCIe-7856
Connection
Accessory
AISENSE
AIGND
V
cm
V
1
+
–
+
–
Overvoltage
Protection
AI–
Overvoltage
Protection
Overvoltage
Protection
Connecting Differential Voltage Signals
You can connect grounded or floating differential signal sources to the PCIe-7856. Connect the
positive voltage signal to the AI+ and the negative voltage signal to AI-. To connect grounded
differential signals to the PCIe-7856, you must also connect the signal reference to AI GND.
Figure 4. Connecting Grounded Differential Signals to the PCIe-7856
PGIA
ADC
AI+
NI PCIe-7856
Connection
Accessory
AISENSE
AIGND
V
cm
V
1
+
–
+
–
Overvoltage
Protection
AI–
Overvoltage
Protection
Overvoltage
Protection
To connect floating differential signals to the PCIe-7856, you must connect the negative and
positive signals to AI GND through 1 MΩ resistors to keep the voltage within the common-
mode voltage range. If the voltage source is outside the common-mode voltage range, the
PCIe-7856 does not read data accurately.
4
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NI PCIe-7856 User Manual
