National Instruments NI USB-621x - Manual (Page 27)

© National Instruments Corporation 4-1 NI USB-621x User Manual
4
Analog Input
Figure 4-1 shows the analog input circuitry of NI 621x devices.
Figure 4-1. M Series Analog Input Circuitry
Analog Input Circuitry
I/O Connector
You can connect analog input signals to the M Series device through the I/O
connector. The proper way to connect analog input signals depends on the
analog input ground-reference settings, described in the
Analog Input
Ground-Reference Settings section. Also refer to Appendix A,
Device-Specific Information , for device I/O connector pinouts.
MUX
Each M Series device has one analog-to-digital converter (ADC). The
multiplexers (MUX) route one AI channel at a time to the ADC through the
NI-PGIA.
DIFF, RSE,
or NRSE
I/O Connector
AI <0.. n>
MUX
AI SENSE
AI GND
NI-PGIA
AI Terminal
Configuration
Selection
Input Range
Selection
ADC AI FIFO AI Data
Digital
Isolators
Isolation
Barrier
(USB-6215
and USB-6218
devices only)