Q: I have other USB devices, like my mouse and keyboard, that sometimes don't respond to the PC or wake up with my laptop. Is USB really a reliable bus for data acquisition?
Absolutely. Though reliability is not a key concern for some peripherals such as joysticks or keyboards, NI CompactDAQ was designed for high-performance data acquisition and operates properly if connected to a compliant USB port and powered within the specified range. There are several NI technologies at work to make NI CompactDAQ the high-quality data acquisition platform it is. Read Three Technologies that Drive USB Performance to learn more about this topic.
Q: Where can I get technical specifications for the NI CompactDAQ carrier and modules?
You can find NI CompactDAQ carrier and module technical information in the products’ user manuals, which are linked from the model page of each product. In addition to the model pages, you can find all National Instruments manuals online at ni.com/manuals. For a complete list of modules available for use in the NI CompactDAQ chassis, see the C Series Module Compatibility Chart
Q: How do I configure and order an NI CompactDAQ system?
The NI CompactDAQ Advisor is an online tool that takes you step by step through your module, chassis, and accessory selection. You can then print an itemized list, e-mail your system configuration, get a quote, or visit the online store to purchase your customized system.
Q: Which applications can NI CompactDAQ handle?
NI CompactDAQ is a general-purpose data acquisition and control system that you can implement in a wide range of applications. It uses open software to run built-in data-logging programs for simple applications or to develop custom acquisition, analysis, control, and display programs for more demanding applications. NI CompactDAQ hardware and software are simple to use for quick benchtop measurements, small enough to take in the field with a laptop, and powerful enough to handle production line testing and light ATE. Customers are using NI CompactDAQ for applications ranging from in-vehicle test to environmental data logging to portable vibration monitoring.
Q: How do I use NI CompactDAQ for data logging?
NI CompactDAQ provides the acquisition and storage capabilities of traditional PC-based data loggers as well as a way to customize your data logger with modular I/O and powerful software options.
To use NI CompactDAQ for data logging, first customize your NI CompactDAQ system with I/O modules to meet your channel count and measurement type requirements. You may find it helpful to use the online NI CompactDAQ Advisor when configuring your system.
Next, select the software package that best meets your needs from the three levels of data-logging software offered with NI CompactDAQ.
- LabVIEW SignalExpress LE – FREE, interactive data-logging software that is shipped with each NI CompactDAQ system
- LabVIEW SignalExpress – full-featured, interactive data-logging software
- LabVIEW – complete, graphical development environment for creating custom data-logging applications
Q: To use NI CompactDAQ, which software is required?
National Instruments ships NI CompactDAQ with an NI-DAQmx driver kit for Windows operating systems. NI-DAQmx offers application programming interfaces (APIs) for development with LabVIEW, C/C++, Visual Basic 6.0, and Visual Studio .NET programming languages.
In addition to NI-DAQmx, National Instruments ships free measurement services software for configuring your system, testing your system, and completing basic data-logging tasks.
- Measurement & Automation Explorer (MAX) – software to save time configuring, testing, and calibrating your NI CompactDAQ system
- LabVIEW SignalExpress LE – FREE data-logging software for acquiring, viewing, and logging data from any NI-DAQmx device
National Instruments also offers the following software options, each of which is designed for optimized integration with NI-DAQmx and NI CompactDAQ.
- LabVIEW SignalExpress – full-featured, interactive data-logging software
- LabVIEW – graphical development environment for data acquisition, analysis, and presentation
- LabWindows™/CVI – ANSI C application development environment for data acquisition
- Measurement Studio – add-on development tools for Visual Studio .NET, Visual Basic, and Visual C++
Q: Does NI CompactDAQ come with a warranty?
The quality of NI CompactDAQ is ensured by a one-year warranty. Should the device fail due to a manufacturing defect within one year of purchase, you can return it to National Instruments for repair/replacement at no charge.
Q: How do I get technical support for NI CompactDAQ?
Visit ni.com/compactdaq for resources to aid in assembly and startup. For assistance and troubleshooting, visit ni.com/support. NI applications engineers can assist you through Web forums and e-mail or by phone.
Q: Am I guaranteed to achieve the acquisition rates that are specified?
All rates specified are for National Instruments C Series modules and the NI CompactDAQ chassis. These rates do not take into account program architecture or PC processing speed. Using computers with older processors or a non-Hi-Speed USB port limits your ability to use NI CompactDAQ to its design specifications. Buffer overflow errors are a common indication that the data acquisition hardware is supplying data at a rate faster than the PC can process it. Internal benchmarks have achieved analog rates of over 5MS/s. If you have questions about the potential performance of your NI CompactDAQ system, please call the NI sales department.
Q: Where can I get more NI CompactDAQ information?
The main NI CompactDAQ home page at ni.com/compactdaq features technical white papers such as the following:
NI CompactDAQ Under the Hood - Three Technologies that Drive USB Performance
Q: What is the difference between the NI cDAQ-9172 chassis and the new generation of chassis, the NI cDAQ-9174 and cDAQ-9178?
| |
cDAQ-9172
|
cDAQ-9174
|
cDAQ-9178
|
| Number of slots |
8
|
4
|
8
|
| Number of AI timing engines |
1
|
3
|
3
|
| Number of DIO timing engines |
0, Alternate correlated clock required
|
1, Internal timing available
|
1, Internal timing available
|
| Number of counters |
2
|
4
|
4
|
| Advanced counter functionality |
No
|
Yes
|
Yes
|
| Hardware-timed digital |
Slots 1–4 only
|
Any slot
|
Any slot
|
| Hardware-timed AO channels |
16
|
As many as necessary
|
As many as necessary
|
| Power Connector |
NI supplied barrel connector
|
Screw Terminals
|
Screw Terminals
|
| Built-in USB cable strain relief |
No
|
Yes
|
Yes
|
| Built-in external trigger connections |
No
|
No
|
Yes (BNC)
|
Q: What is the “Advanced Counter Functionality” that the new generation of NI CompactDAQ chassis are described as having?
The cDAQ-9174/78 chassis contain four 32-bit advanced functionality counter/timer chips in the chassis backplane. These counters are capable of performing the traditional input and output operations. However, each counter has a new embedded counter, which gives you the ability to perform, with one counter, the tasks that previously required the use of two. For example, the generation of finite pulse trains, which in the past reserved two counters, will now only require one counter.
Q: What material is NI CompactDAQ made of? It looks like plastic in the images.
NI CompactDAQ is made of metal (A380), which makes it rugged enough to survive the rigors of field, track, or even some industrial test use. The chassis has a 30 g shock rating and a -20 to 55 °C temperature rating.
Q: How do I synchronize two chassis together for higher-channel systems?
Each cDAQ-9172 chassis has an internal timing controller, the NI-STC 2 chip. You can access the pins to this chip by placing a correlated digital I/O module (hardware-timed like the NI 9401) into slots five or six of the chassis. Using the digital module and the NI-STC 2 of each chassis to be synchronized, you can route the sample clock from one chassis into the connected chassis. This requires two chassis and two of the digital modules installed in slot five or six of each chassis. See the Synchronizing Multiple NI CompactDAQ Chassis tutorial for more information.
The cDAQ-9178 chassis uses the NI-STC 3 technology for the internal timing controller. The pins of this controller can be accessed, among other ways, through the two BNC connectors of the chassis. The sample clock and triggers necessary for synchronization of multiple chassis can be routed through these connectors as well. Alternately, a hardware-timed digital module can be used just as it would be in the cDAQ-9172 as described in the Synchronizing Multiple NI CompactDAQ Chassis tutorial.
Q: Is there a GPIB interface for NI CompactDAQ?
No. GPIB throughput is far too slow. The data rates needed by some of the higher-speed applications are far too great for older bus technology. Hi-Speed USB provides the ease of use, bandwidth, and availability required for today’s data acquisition systems.
If GPIB connectivity is necessary for your application, consider the NI GPIB-USB-HS.
Q: Does the CAN module for CompactRIO work in NI CompactDAQ?
No. NI CompactDAQ does not support the CAN module, but National Instruments does have a solution to synchronize NI CompactDAQ with one of several NI CAN interfaces, including the PCMCIA CAN card. See the application note below for more information on this system setup.
Q: Can I run different modules in the chassis at different rates?
The new generation of NI CompactDAQ chassis, the cDAQ-9174 and cDAQ-9178, have three analog input timing engines. Up to three AI tasks, each with a unique set of modules, can run at different rates.
The cDAQ-9172 chassis has one internal timing engine each for analog input and analog output tasks. Therefore, though there may be more than one analog input module in the chassis, all the AI channels must be bundled into one AI task and run at the same hardware-timed rate. Likewise, analog output channels must be bundled into a single AO task with one update rate, though this rate can be different from that of the AI task.
Q: Some of the “new” modules have the same model number as modules that have been shipping for the National Instruments CompactRIO platform for some time now. Are these the same?
Yes. Some of these modules that have sold for the CompactRIO platform are now compatible with the NI CompactDAQ platform. If you already have one of these CompactRIO modules, you can use it in an NI cDAQ-917x chassis even though it may have an “NI cRIO-9xxx” model number on it. Just make sure you download the latest version of NI-DAQmx driver software, which is compatible with these new modules. The NI-DAQmx readme.txt file lists compatible NI CompactDAQ modules.
Q: Do all C Series modules work in both the NI CompactDAQ and CompactRIO platforms?
No. There are some modules that work with CompactRIO but not NI CompactDAQ. See the C Series Module Compatibility Chart.
Q: Will modules that worked with the cDAQ-9172 chassis work with the new cDAQ-9174/78 chassis?
Yes. All the modules that were available for the cDAQ-9172 will work with the new generation of chassis.
Q: Some of the C Series modules have their own single module carrier (NI USB-9162). Where can I see a complete list of the modules that work with the USB single module carrier or the wireless/Ethernet carrier (NI WLS-9163)?
For information about which modules are compatible with each carrier, see the C Series Module Compatibility Chart.
Q: In the C Series Module Compatibility Chart, I don’t see a quadrature encoder measurement module. Can NI CompactDAQ measure quad encoders?
Yes. The NI CompactDAQ chassis contains 32-bit counter/timer chips in the chassis backplane that perform both input and output operations. Access the source, gate, and count lines by installing a correlated digital I/O module (hardware-timed like the NI 9401) into any slot of the cDAQ-9174/78 chassis or into slot five or six of the cDAQ-9172 chassis. Once you have inserted the module, you can configure counter/timer angular position measurement tasks through the driver.
Q: What are the capabilities and limitations of Hi-Speed USB?
Hi-Speed USB provides a plug-and-play interface for connecting NI CompactDAQ to either a desktop or a laptop computer. With a 480 Mb/s data rate, Hi-Speed USB offers sufficient bandwidth for an entire NI CompactDAQ chassis full of dynamic acquisition modules.
One of the primary advantages of USB for PC-based data acquisition is the ability to extend the system away from the PC itself. However, the USB specification limits the distance between port and device to 5 m. You can use up to five USB hubs to extend the device beyond the 5 m cable limit.
Q: Can I run more than one NI CompactDAQ chassis off of a hub with no decrease in performance?
In many cases, yes. USB is a shared-bandwidth bus meaning the 60 MB/s throughput is used by all devices that are connected to the same root hub. The number of modules and the rate of acquisition dictate how much bandwidth NI CompactDAQ uses, but internal NI benchmarks show that two chassis can acquire analog input data at maximum rate on many newer model computers.
Q: I see the new locking USB cable on the cDAQ-9174/78 chassis. Will a regular USB cable work with this connector?
The locking (captive) USB cable and connector were added to the chassis design for strain relief and to ensure the system’s ruggedness. You can now use a thumbscrew on the cable to screw the USB cable to the chassis to prevent accidental disconnects during operation. This cable is included in the shipping kit with the chassis. It is an off-the-shelf standard part that you can order should the cable need to be replaced. However, you can plug a regular USB cable without the thumbscrew into the chassis should the need arise.
Q: How long can a USB cable be?
USB specifications dictate 5 m, but there are some companies that make USB extenders and some off-the-shelf passive USB repeaters that can extend the 5 m limit. The 5 m is a single-cable limit, and you can use up to five hubs to extend the reach of the USB signal.
Q: What about wireless USB hubs?
USB wireless hubs are beginning to emerge in the marketplace and, just as with wired hubs, quality of design and construction can dramatically affect performance when it comes to high-quality data acquisition. We have not yet found a wireless USB extender that has the performance to support the high speed data rates of NI CompactDAQ. For remote measurements, many of the most popular modules work in the Ethernet and Wi-Fi carriers. See the C Series Compatibility Chart for supported modules.
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