National Instruments NI PCIe-7857 User Manual page 5

To connect non-referenced single-ended voltage signals to the PCIe-7857, 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-7857
+
V
1
–
+
V
cm
–
Connecting Differential Voltage Signals
You can connect grounded or floating differential signal sources to the PCIe-7857. Connect the
positive voltage signal to the AI+ and the negative voltage signal to AI-. To connect grounded
differential signals to the PCIe-7857, you must also connect the signal reference to AI GND.
Figure 4. Connecting Grounded Differential Signals to the PCIe-7857
+
V
1
–
+
V
cm
–
To connect floating differential signals to the PCIe-7857, 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-7857 does not read data accurately.
4 | ni.com | NI PCIe-7857 User Manual
AI+
AI–
AISENSE
AIGND
Connection
Accessory
AI+
AI–
AISENSE
AIGND
Connection
Accessory
Overvoltage
Protection
Overvoltage
Protection
Overvoltage
Protection
Overvoltage
Protection
Overvoltage
Protection
Overvoltage
Protection
PGIA ADC
NI PCIe-7857
PGIA ADC
NI PCIe-7857