© National Instruments Corporation 11 NI cDAQ-9178/9174 User Guide and Specifications
Using the NI cDAQ-9178/9174
The cDAQ system consists of three parts: C Series I/O modules, the cDAQ module interface, and the
USB-STC3, as shown in Figure 8. These components digitize signals, perform D/A conversions to
generate analog output signals, measure and control digital I/O signals, and provide signal conditioning.
Figure 8. NI cDAQ-9178/9174 Block Diagram
C Series I/O Modules
National Instruments C Series I/O modules provide built-in signal conditioning and screw terminal,
spring terminal, BNC, D-SUB, or RJ-50 connectors. A wide variety of I/O types are available, allowing
you to customize the cDAQ system to meet your application needs.
C Series I/O modules are hot-swappable and automatically detected by the NI cDAQ-9178/9174 chassis.
I/O channels are accessible using the NI-DAQmx driver software.
Because the modules contain built-in signal conditioning for extended voltage ranges or industrial signal
types, you can usually make your wiring connections directly from the C Series I/O modules to your
sensors/actuators. In most cases, the C Series I/O modules provide isolation from channel-to-earth
ground.
For more information about which C Series I/O modules are compatible with the NI cDAQ-9178/9174
chassis, refer to the KnowledgeBase document, C Series Modules Supported in the NI cDAQ-9178/9174
CompactDAQ. To access this KnowledgeBase, go to
ni.com/info and enter the info code rdcdaq.
Hardware-Timed Versus Static DIO Modules
Digital I/O module capabilities are determined by the type of digital signals that the module is capable
of measuring or generating. Static digital I/O modules are designed for signals that change slowly and
are accessed by software-timed reads and writes. Hardware-timed digital I/O modules are for signals
that change rapidly and are updated by either software-timed or hardware-timed reads and writes. For
more information about digital I/O modules, refer to the Digital I/O section.
cDAQ Module Interface
The cDAQ Module Interface manages data transfers between the USB-STC3 and the C Series
I/O modules. The interface also handles autodetection, signal routing, and synchronization.
C Series
I/O Module
C Series
I/O Module
C Series
I/O Module
cDAQ Module
Interface
USB-STC3
USB 2.0
Chassis
PFI Terminals
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