Terry Stratoudakis, P.E. - ALE System Integration
Lawrence M. David Jr - ALE System Integration
When a local high-tech electronics firm was awarded the contract to supply a communications interface hub for a Navy surveillance aircraft, it was also tasked with designing digital test equipment (DTE) to verify the initial functionality of the interface and provide ongoing verification for 20 years of field maintenance. Using a PXI platform from National Instruments, ALE System Integration provided expertise in hardware integration and software development for the system.
The interface unit (the end product being tested) was designed to coordinate all the aircraft’s digital and analog signal routing, including the internal intercom, external radio, radar, and all digital instrumentation. The interface needs to correctly process all appropriate signals while ignoring corrupted signals and noise. To verify this functionality, the DTE needed to inject all valid and invalid signals and interpret the interface’s responses.
In addition to verifying the aircraft’s functionality, the DTE needed the capability to perform a self-test operation and the flexibility to perform a one-time design verification including all flight-worthiness tests; additional electromagnetic interference tests; and a series of physical tests such as the highly accelerated life test (HALT), explosive atmosphere, salt atmosphere, and thermal cycling. The DTE also had to be able to inject and interpret the wide range of signals onboard the aircraft including analog audio, serial (9600 baud), high-speed digital (5 MHz), and MIL-STD 1553, a military standard serial data bus that features a dual redundant balanced line physical layer, time division multiplexing, and a half-duplex command/response protocol.
Designing the DTE with PXI Hardware from National Instruments
The DTE was implemented using an NI PXI-8196 embedded controller containing the following modules: NI PXI-6513, NI PXI-6542, NI PXI-2569, NI PXI-6511, and NI PXI-4060.
The PXI-6542 module was used at a clock speed of 20 MHz allocating four bits per tick of the 5 MHz device-under-test (DUT) clock, thus improving test accuracy. The NI-HSDIO software greatly reduced development time. The system also included a Condor QPC-1553 from GE Fanuc Embedded Systems that included LabVIEW drivers to further simplify software development.
We also used two programmable power supplies, a 3-phase AC supply (GPIB) at 400 Hz to mimic the aircraft’s power, and a DC supply (USB) to mimic internal supply circuitry. Both programmable power supplies were interfaced to the system via the USB and GPIB ports of the PXI-8196 embedded controller.
Analyzing Digital Test Data with LabVIEW
With a graphical user interface (GUI) developed using LabVIEW software, the technician experiences improved flexibility in configuring test runs of any of the 10 categories of tests in addition to a DTE self-test. The analysis capabilities of LabVIEW were instrumental in filtering and cross-referencing results from multiple categories of tests to pinpoint circuitry defects.
One constraint of this project was the simultaneous development of the test system and the interface unit. However, two major advantages of using LabVIEW to develop this system were the prototyping and debugging capabilities including custom probes and highlighted execution. The code developed for the test system was reused to carry on the ongoing tests for the system.
We were able to develop the test system with ongoing changes to the specification and give invaluable support to our client in their own development process. The key to this success was the NI Digital Waveform Editor software. With this tool, our client created digital waveform files using the editor, which we then fed into the test system. The resulting digital data file was easy for our client to review.
Overall, this was a great experience for our client. Using the LabVIEW and PXI platform, we delivered software faster than our client expected, and we were able to integrate seamlessly with their team.
Terry Stratoudakis, P.E.
ALE System Integration
Tel: (631) 421-1198