National Instruments NI 6221, User Manual

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© National Instruments Corporation 4-1 M Series User Manual
4
Analog Input
Figure 4-1 shows the analog input circuitry of M Series devices.
Figure 4-1. M Series Analog Input Circuitry
The main blocks featured in the M Series analog input circuitry are as
follows:
• 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.
• Ground-Reference Settings —The analog input ground-reference
settings circuitry selects between differential, referenced single-ended,
and non-referenced single-ended input modes. Each AI channel can
use a different mode.
• Instrumentation Amplifier (NI-PGIA) —The NI programmable gain
instrumentation amplifier (NI-PGIA) is a measurement and instrument
class amplifier that minimizes settling times for all input ranges. The
DIFF, R S E,
or NR S E
I/O Connector
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M u x
AI S EN S E
AI GND
NI-PGIA
AI Termin a l
Config u r a tion
S election
Inp u t R a nge
S election
ADC AI FIFO AI D a t a
AI Lowp ass
Filter