Project Objectives
- Design and implement a highly configurable data acquisition system that supports a wide range of sensor types, channel counts, and acquisition speeds.
- Provide an intuitive user interface, allowing for monitoring and configuration of the distributed system from a centralized location, including:
- Configuration of channel properties and signal conditioner settings
- Automatic channel calibration and scaling routine using voltage insertion
- Live data monitoring across all channels, both during test time and during setup/monitoring phases
- Easy export of test data from a distributed network of digitizers to a central location
- Diagnostic tools for pre-test I/O checks
- Synchronize data acquisition across a distributed network of real-time digitizers, aligning both recording start latency and clock spread.
- Provide a redundant system of independent signal digitizers, to mitigate the risk of data loss due to hardware failure.
- Exchange test configuration, sensor data, and status information with an external process control system.
Phase 1: Requirement Analysis & Planning
DMC first conducted numerous onsite and offsite meetings with the customer and various external stakeholders to establish design objectives and requirements. From these meetings, we identified the required hardware and software needed to meet our customer’s design objectives. We conducted design review meetings with the facility end users to refine test setup and execution workflow and presented detailed UI mockups to aid in these discussions.
After several rounds of design review, the finalized hardware and software design was translated into a Functional Specification document. In addition to system hardware diagrams, this document included detailed state-machine logic flow diagrams and UI mockups for reference by the DMC team during software development. The final software specification consisted of an NI LabVIEW PC application that serves as the front-end for the distributed system, as well as a lightweight NI Linux Real-Time application that is responsible for data acquisition and logging.
Phase 2: System Design & Development
While this project consisted of two data acquisition systems for two very different facilities, DMC identified many core similarities early in the design process, which allowed for significant overlap in the initial system design.
- NI PXI and cRIO Digitizer Platforms: Given the system’s high channel count and high-speed data acquisition requirements, DMC selected a combination of NI’s PXI and cRIO platforms for signal digitization. The cRIO is an especially rugged, small, and low-power platform ideal for the extreme environmental conditions present in some areas of this distributed system, while both platforms provide powerful processors, high channel counts, and support for time synchronization protocols.
- Precision Filters & PCB Signal Conditioner Platforms: To meet the system’s rigorous calibration requirements and to provide support for a wide range of signal types, DMC selected the Precision Filters 28000 series of signal conditioners. The external “Test Bus” feature of the 28000 chassis allowed for automatic multi-channel calibration via voltage insertion from an external Source Meter. DMC also selected the PCB 483C41 signal conditioner for a smaller subset of IEPE-type signals. These devices are responsible for taking in signals from a wide array of sensor types and converting them into uniform voltage signals to feed into the digitizers. The separation of signal conditioning and digitization across these different hardware platforms allowed for maximum system flexibility, supporting over 10 different sensor types while keeping the digitization system simple and lightweight.
- IEEE 1588 Precision Time Protocol: Due to the customer’s rigorous data acquisition synchronization requirements, DMC selected the Microchip SyncServer S650 with GPS antenna, using IEEE 1588 Precision Time Protocol to synchronize the digitizers across this distributed system. The NI controllers’ support for IEEE 1588 PTP v2.1 protocol allows for easy integration with this timing source.
- NI LabVIEW Linux Real-Time: DMC selected LabVIEW Linux RT as the software platform for the PXI and cRIO digitization and data logging applications due to its seamless compatibility with these NI controllers. Leveraging object-oriented programming, DMC developed a single application to encompass both controller types, which allowed for ease of maintainability and a uniform external interface from all digitization devices. This application is responsible for continuously acquiring data at a configurable sample rate, applying channel scaling, streaming data over TCP and UDP protocols to external applications, and, during test time, recording data to disk in the TDMS file format.
- NI LabVIEW Windows: For the front-end of this large distributed system, DMC utilized a Windows PC running an NI LabVIEW application. DMC leveraged the DMC LabVIEW UI Suite to minimize user-interface development time while providing a modern and easy-to-navigate operator interface. This LabVIEW front-end application is responsible for orchestrating calibration, data acquisition, data export, data monitoring, and diagnostic activities across the large, distributed network of digitizers, signal conditioners, and additional test hardware. DMC leveraged object-oriented software design to maintain a single LabVIEW PC application for both facilities while implementing the unique features required by each end user team.
- LabVIEW Actor Framework Architecture: DMC leveraged the Actor Framework LabVIEW architecture across the Windows PC and Linux Real-Time applications. The modularity of the actor framework allowed for a rapid initial development phase, with many engineers working simultaneously on separate actors for various portions of the system. On the Real-Time side, DMC developed actors responsible for each of the critical portions of the application, including data acquisition and data logging. The lightweight and asynchronous nature of these actors allowed us to meet the system’s extremely rapid data acquisition speed requirements reliably. Aligning this architectural decision across the PC and Real-Time applications enabled seamless communication and integration throughout the system.
Phase 3: Testing & Prototyping
- Device Driver Testing: Leveraging DMC’s large team of LabVIEW engineers, the initial phase of the project was carried out by a nationwide team. Driver-level device modules were thoroughly tested by DMC software developers at various DMC offices before integration into the larger applications. This greatly simplified the testing process of the full LabVIEW applications.
- System Prototype: After developing the initial PC and Real-Time LabVIEW applications, the team assembled a full system prototype at DMC’s Chicago headquarters. By setting up one of each key system hardware element in a prototype setting, DMC was able to test the full system functionality early on, identifying and resolving any issues long before full system commissioning. DMC was able to demonstrate this system to the customer and end users, which provided an opportunity for valuable hands-on operator training and user feedback early in the development process. DMC was able to quickly implement feedback and feature requests from these initial demonstrations to ensure the final system would meet all user needs.
Phase 4: Implementation & Commissioning
- Staged Deployment: DMC coordinated with the end user team and external stakeholders to create a phased testing and acceptance plan, designed to ensure the system met all requirements laid out in the initial functional specification document.
- Training and Support: We provided comprehensive training to the facility’s engineering and operations team on the new system, ensuring they were well-versed in the new features and functionalities. This included detailed operations and maintenance manuals for the system, onsite operator training, and ongoing coordination meetings with the end users.
Conclusion
The successful deployment of two advanced distributed high-speed data acquisition systems demonstrates DMC’s deep expertise in LabVIEW development and National Instruments Real-Time platforms, while highlighting our knowledge in designing high-speed data acquisition systems for the unique requirements of the Aerospace and Defense industry. By leveraging our extensive experience in these areas, DMC delivered a robust, scalable solution that meets the demanding requirements of aerospace testing environments. Our proven methodology in handling large-scale test and measurement projects positions our aerospace and defense clients for continued success in their most demanding test applications.
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