NI CompactDAQ Technology

This document describes some of the under-the-hood technologies and features that make NI CompactDAQ a simple, complete data acquisition system. Designed for performance, these chassis incorporate knowledge gained from years of experience in the test and measurement industry. Many of the technologies discussed in this paper set NI CompactDAQ apart from other devices on the market.

1. C Series Modules
2. Mechanical Design
3. Multiple Timing Engines for Multiple Acquisition Rates
4. Advanced Counter Functionality From NI-STC 3 Technology
5. NI Signal Streaming Technology
6. Software Options with NI CompactDAQ
7. Purchasing Information

C Series Modules

Choose from more than 50 NI C Series modules for different measurements including thermocouple, voltage, resistance temperature detector (RTD), current, resistance, strain, digital (TTL and other), accelerometers, and microphones. Channel counts on the individual modules range from three to 32 channels to accommodate a wide range of system requirements. C Series modules combine signal conditioning, connectivity, and data acquisition into a small module for each specific measurement type. Insert these modules into any C Series chassis to create a variety of systems. Finally, you can create a mix of channel counts and measurement types within one system by selecting the desired modules and installing them into one of several C Series systems. With the NI CompactDAQ, you can build the right system to meet the needs of your measurement application.

Figure 1. Choose from more than 50 NI C Series measurement modules.

Mechanical Design

Placement and installation of instrumentation are important parts of a test setup. By placing instrumentation close to the test subject, you can minimize electrical noise from the surroundings. This is because digital signals, used by USB, Ethernet, 802.11 Wi-Fi, and several other protocols, are significantly less susceptible to electromagnetic interference. NI CompactDAQ is designed to measure many channels in a small, rugged package so that you can place it close to the unit under test. NI CompactDAQ systems offer the following mechanical design features:

Rugged, Versatile Chassis With Flexible Mounting Options

• Ability to hold 1, 4, or 8 C Series modules 
• Trasnfer data over USB, Ethernet, or 802.11 Wi-Fi or choose a stand-alone option with an embedded computer
• A380 metal construction for durability
• 30 g shock and 0.3 g_rms operational vibration in accordance with IEC-60068-2-27/64
• -20 to 55 °C operational temperature for most chassis
• Panel mount, rack mount, DIN-rail mount, and desktop mounting kits
• 2D and 3D dimensional drawings (see Resources tab on model pages)

Figure 2. NI CompactDAQ chassis offer 1-, 4-, or 8-slot options.

Cable and Signal Wire Strain Relief for Solid Connections

• Power connection is attached to chassis with screws and includes a protective backshell for safety
• USB cable locks to USB chassis with thumbscrew (locking USB cable included in USB chassis kits)
• Ethernet cable locks with latch mechanism (standard Ethernet cable sold separately)
• All modules either are shipped with or have available as accessories strain relief covers to prevent wire removal
• Shock and vibration tests are conducted with power, communication, and module signal wires connected

Built-In Trigger Lines for Import/Export of Digital Clocks

• 8-slot USB and Ethernet chassis have two BNC connections for trigger lines
• Bandwidth to support up to a 1 MHz clock
• Ability to synchronize multiple systems (system synchronization not compatible with all modules, see chassis manual)

Figure 3. Close-up of power input, BNC trigger lines, and locking USB port on the NI cDAQ-9178

Automatic Synchronization of Modules and Channels

• Add more measurement types and channels to the system by simply plugging in additional modules
• Modules are hot-swappable and autodetect once you insert them into a CompactDAQ chassis
• A single NI CompactDAQ system can simultaneously stream high-speed analog input, analog output, digital input, and digital output

Visit the NI CompactDAQ chassis model page for prices and ordering information.

Multiple Timing Engines for Multiple Acquisition Rates

A vital piece of a DAQ system is the analog-to-digital converter (ADC). ADCs need clock signals to designate when samples are to be acquired. Many systems have multiple ADCs that share the same clock to synchronize all of the channels’ measurements. NI CompactDAQ systems have the advantage of flexibility when it comes to timing engines and go beyond this standard synchronization.

Multiple Timing Engines for Multiple Rates

NI CompactDAQ chassis have three analog input timing engines. This enables programmers to divide all of their analog inputs in up to three different groups known as “tasks.”

• Each task can run at a separate rate, as seen in Figure 3. This is ideal when combining temperature measurements, which are often slow, with higher-speed measurements such as sound and vibration.
• The three tasks operate independently, can be addressed from separate loops or threads in a program, and can be started simultaneously.
• All channels within a single task are automatically synchronized. In the event a multiplexed module is combined in a task with a simultaneous sampling module, the first channel in the multiplexed module is synchronized and the subsequent channels in the multiplexed module scan through in succession.
• All channels within a single task, simultaneous and multiplexed, are returned at the requested sample rate.
• All modules can be placed in a single task if desired. This synchronizes all channels to the same clock.

Designated Timing Engines for Digital and Analog Output

NI CompactDAQ was designed to perform up to seven tasks simultaneously. You can choose from several task options:

• Analog input with up to three timing engines
• Digital input with designated timing engine
• Digital output with designated timing engine
• Analog output with designated timing engine
• Counter/timer tasks for quadrature, PWM, event, period, or frequency measurement (there are four counter/timers built into NI CompactDAQ chassis that you can access through a digital module)

By having a designated resource, digital and analog output tasks can run independently without having to share a clock signal from another task. This makes the programming easier and more intuitive. Designated resources can be shared with other subsystems of the chassis. For example, you can share the digital input clock with the analog output clock to generate a voltage with every rising/falling edge of the digital input.

The multiple timing engines and ability to route and share resources provide a level of flexibility to NI CompactDAQ unequaled by most off-the-shelf data acquisition systems.

Figure 4. This image depicts different analog input tasks running at different rates in the same chassis.

Advanced Counter Functionality From NI-STC 3 Technology

Some of the core technology in NI CompactDAQ chassis is shared with other NI data acquisition products. This technology is known as the third generation of the system timing controller (NI-STC3). Many devices use off-the-shelf clocks and oscillators for system timing. NI technology is designed for performance from the ground up, starting with the timing engines and 30 years of PC-based instrumentation experience. NI-STC3 technology is proprietary source code that is built into an ASIC and separates systems like NI CompactDAQ from all other devices on the market.

Four Advanced 32-Bit Counter/Timers

• You can use counters for event counting, quadrature encoder measurement, PWM, pulse train generation, or period or frequency measurement.
• NI-STC3 counters are advanced because they contain an embedded or onboard auxiliary counter. This is not directly accessible by the user, but it is accessed by the driver for some frequency measurements. These processes normally require two cascaded counters, but with NI-STC3 technology, these advanced counters can do more with fewer resources.
• You can share resources to synchronize counter tasks to other counter, digital, or analog tasks.

Figure 4. Diagram of Counter 0 and Frequency Generator

Built-In Frequency Generator

• 10 MHz, 20 MHz, 100 kHz base clocks
• 16 divisors (n=1..16)
• Output through an installed hardware-timed digital module or built-in BNC trigger lines (1 MHz bandwidth limit on built-in trigger lines)

Advanced Counter and Digital Features

• Change detection event
• Hardware triggering (start, reference, and pause)
• Programmable function interface (PFI) terminals used for input/output timing signals for analog, digital, or counter functions
• Eight counter input functions
• Five counter output functions

NI Signal Streaming Technology

Communication buses, such as USB and Ethernet, and 802.11 Wi-Fi have a standardized data structure and a defined method of how a device communicates with the host, but not all devices are created equal. Patented NI Signal Streaming technology sets out to operate NI data acquisition devices most efficiently within the bounds of these bus standards. Many consumer products need only one or two streams of directional data. Music players and storage devices often move large quantities of data in one direction, updating to or from the host PC. Test systems often involve multiple inputs and outputs running simultaneously. NI Signal Streaming technology enables high-speed, bidirectional data streaming to and from the NI CompactDAQ system.

Figure 5. NI Signal Streaming technology enables parallel streaming of data from multiple tasks with minimal processor involvement.

Read the NI Signal Streaming white paper.

Software Options with NI CompactDAQ

With NI CompactDAQ data acquisition systems, you can develop measurement and test applications in multiple programming environments, including ANSI C/C++, C#, and Microsoft Visual Basic .NET. However, tight hardware/software integration makes the NI LabVIEW graphical development environment the best choice for getting the most performance out of your NI CompactDAQ system with the least programming effort.

NI LabVIEW is a graphical programming environment for developing sophisticated measurement, test, and control systems using intuitive graphical icons and wires that resemble a flowchart. LabVIEW offers unrivaled integration with thousands of hardware devices, including NI CompactDAQ, and provides hundreds of built-in libraries for advanced analysis and data visualization. You can automate measurements from several devices, analyze data in real time, and create custom reports in just minutes using this industry-standard tool.

Figure 6. Graphical programming and dataflow representation make you more productive, enabling you to program just like you think.

Purchasing Information

Configure Your Own NI CompactDAQ System
Browse Preconfigured NI CompactDAQ Systems
View Pricing and Specifications for NI CompactDAQ Chassis

14 Ratings | 4.07 out of 5

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