National Instruments Data Acquisition Device NI USB-621x - Floating Signal Sources

Chapter 4 Analog Input
NI USB-621x User Manual 4-24 ni.com
Table 4-2. USB-6210/6211/6212 Analog Input Configuration
AI Ground-Reference
Setting
*
Floating Signal Sources
(Not Connected to
Building Ground)
Ground-Referenced
Signal Sources
†
Examples:
•Ungrounded thermocouples
• Signal conditioning with
isolated outputs
• Battery devices
Example:
•Plug-in instruments with
non-isolated outputs
Differential (DIFF)
Non-Referenced
Single-Ended (NRSE)
Referenced Single-Ended
(RSE)
*
Refer to the Analog Input Ground-Reference Settings section for descriptions of the RSE, NRSE, and DIFF modes and
software considerations.
†
Refer to the Connecting Ground-Referenced Signal Sources section for more information.
+
–
+
–
AI+
AI–
AI GND
Signal Source DAQ Device
+
–
+
–
AI+
AI–
AI GND
Signal Source
DAQ Device
V
cm
+
–
+
–
AI
AI SENSE
AI GND
Signal Source DAQ Device
+
–
+
–
AI
AI SENSE
AI GND
Signal Source DAQ Device
V
cm
+
–
+
–
AI
AI GND
Signal Source DAQ Device
Ground-loop potential (V
A
– V
B
) are added
to measured signal.
NOT RECOMMENDED for the
USB-6210/6211/6212
+
–
+
–
AI
AI GND
V
B
V
A
DAQ DeviceSignal Source