NI cDAQ-9178/9174 User Guide and Specifications 22 ni.com
Minimizing Glitches on the Output Signal
When you use a DAC to generate a waveform, you may observe glitches on the output signal. These
glitches are normal; when a DAC switches from one voltage to another, it produces glitches due to
released charges. The largest glitches occur when the most significant bit of the DAC code changes. You
can build a lowpass deglitching filter to remove some of these glitches, depending on the frequency and
nature of the output signal. Go to
ni.com/support for more information about minimizing glitches.
Getting Started with AO Applications in Software
You can use the NI cDAQ-9178/9174 chassis in the following analog output applications:
• Single-Point (On-Demand) Generation
• Finite Generation
• Continuous Generation
• Waveform Generation
For more information about programming analog output applications and triggers in software, refer the
LabVIEW Help or to the NI-DAQmx Help.
The NI-DAQmx Help is available after installation from Start»All Programs»National Instruments»
NI-DAQ»NI-DAQmx Help. To view the LabVIEW Help, select Help»Search the LabVIEW Help in
LabVIEW. Alternately, to download the LabVIEW Help, go to
ni.com/manuals.
Digital I/O
To use digital I/O, insert a digital I/O C Series module into any slot on the NI cDAQ-9178/9174 chassis.
The I/O specifications, such as number of lines, logic levels, update rate, and line direction, are
determined by the type of C Series I/O module used. For more information, refer to the documentation
included with your C Series I/O modules.
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.
Hardware-timed digital I/O modules can be used in any chassis slot and can perform the following tasks:
• Software-timed reads and writes
• Digital waveform generation and acquisition (hardware-timed input/output)
• Counter/timer (up to two modules)
• Access PFI signals (up to two modules)
To determine the capability of digital I/O modules supported by 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 document, go to
ni.com/info and enter the info
code rdcdaq.
Static DIO
Each of the DIO lines can be used as a static DI or DO line. You can use static DIO lines to monitor or
control digital signals on some C Series I/O modules. Each DIO line can be individually configured as
a digital input (DI) or digital output (DO), depending on the C Series I/O module being used.
All samples of static DI lines and updates of static DO lines are software-timed.
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