Creating a Versatile, Sustainable, and Compliant Test Solution for Diverse Weapons Systems Support of Instrumentation and other Avionics

Author(s):

Paul Pankratz - CACI
David Finnie - CACI

Who Is CACI?

CACI provides information solutions and services in support of national security missions and government transformation for Intelligence, Defense, and Federal Civilian clients. A member of the Fortune 1000 Largest Companies and the Russell 2000 Index, CACI provides dynamic careers for approximately 14,900 employees working in more than 120 offices worldwide.

The Decision Process

CACI decided to develop a test system that would meet the DoD’s needs not only in the near term but well into the future. Our goal was to create a test platform that would last as long as the weapon systems it was built to support. In addition, the design would be based on a commercially available solution containing no proprietary hardware, giving the end user the ability to maintain the system hardware without returning to CACI for support.

CACI started by examining potential hardware solutions and analyzing the various technologies at certain points in their lifecycles. CACI was determined to select a technology that had been fielded long enough to ensure it was proven, but also early enough in its lifecycle to ensure it would be around for many years to come.

After reviewing potential solutions on the market, CACI decided to base our test solution on the PXI architecture due to the key features of this technology:

• Footprint: Many of the legacy test systems CACI was targeting for replacement sat on a workbench. In order to minimize the impact to the shop, a key goal was to develop a test system that sits on a workbench in place of the legacy system.
• Strong vendor selection: Because top-tier instrument developers have embraced the PXI architecture, it provided a wide selection of instruments to choose from while designing the test system.
• Best value: CACI also recognized that tight budgets in the maintenance shops drove a need to control costs while meeting or exceeding the test requirements of the legacy system. As such, CACI committed to providing a solution featuring significant capability while controlling costs. This cost control was not only a consideration for the purchase price but also a factor in establishing long-term support, including spare parts and equipment as well as labor to continue system maintenance and calibration.

Once the decision to adopt the PXI form factor was made, CACI next focused on instrument selection. One of the strengths of PXI is the wide selection of instruments available from multiple vendors to meet specific needs. As part of our process, we established the stimulus and response requirements for the initial set of end items to be re-hosted. In addition to evaluating vendors’ instrument capabilities and costs, CACI took into consideration certain qualities of the vendor, including how they responded to inquiries and their reputations within the industry.

Upon completing our analysis and market survey, CACI decided to base the majority of the test solution utilizing National Instruments (NI) technology based on our test requirements and its best value pricing, which allowed us to control unit costs. NI was also able to provide short delivery times, allowing us to complete our prototype development without being impacted by long delays waiting for instruments to be shipped.

We originally named the initial bench-top test solution for the rather narrow range of instruments that it supported, but as we and our customers began to realize that the test systems could serve a much broader range of end items, we updated the name to the Common Bench-top Automatic Test Set (CBATS).

To date, CACI has developed two CBATS models: 101 and 201. The CBATS 101 was the original, lower-cost solution and is the smaller of the two built on an 8-slot PXI chassis. The CBATS 201, the larger of the two systems, is based on an 18-slot PXI chassis and presents a more robust set of test and measurement capabilities. 

The CBATS 201 utilizes the PXI-2532 switch matrix as the conduit for routing the various I/O signals to the measurement instruments (PXI-6221 and PXI-4072). In addition, we incorporated three PXI-2568 single-pole single-throw (SPST) relay modules to route internal power and signal resources to the external interface as well as to provide user-defined switching capabilities. The PXI-5122 digitizer is used in conjunction with two TEGAM 4040A amplifier modules to allow high-speed analysis of signals with peak voltages of up to 100 V. The PXI-7852R field-programmable gate array (FPGA) module is a software-configurable device used to create arbitrary waveforms and phase-locked signals as well as to asynchronously capture and analyze data.

Software Tools

As CACI began evaluating the best tools for developing the system software components and test applications, we had a specific set of criteria to follow. We wanted to leverage the knowledge of our current workforce when possible and to make sure that the tools selected would work together seamlessly. Finally, we wanted to select tools that could quickly and efficiently generate the required applications.

CACI selected NI LabWindows™/CVI for the system software components. To isolate the hardware from the test application, CACI created a hardware abstraction level. This approach ensured minimal impact to the test applications in the event an instrument became obsolete and had to be replaced. CACI was comfortable that LabWindows/CVI would provide the required functionality, and since many NI instruments were included in the design, CACI was confident the software and hardware would integrate well together. And if integration problems were encountered, we would only need to work with one vendor to resolve them.

Many of the early Test Program Set (TPS) software applications CACI completed on the CBATS supported cockpit indicators. A key part of the testing and diagnostics of these systems required visual verification by the maintenance technician of the correct response when simulated aircraft signals were injected into the device. Because of the visual nature of the testing and operator involvement, CACI selected the NI LabVIEW graphical development environment to develop the first set of TPSs on the CBATS. These end items typically did not have any parametric data to be collected, and most test criteria were simple pass/fail or go/no-go results. One of the added benefits of using LabVIEW was the decreased development time to produce the TPSs compared to classical programming languages.

As the types of TPSs being re-hosted evolved, we began developing TPSs for avionics equipment that required little or no operator interaction. These TPSs typically consisted of a series of tests where stimulus was applied to the unit and the expected response was measured. For this type of TPS, CACI selected NI TestStand because it allowed us to quickly develop new TPSs from scratch. During the initial TPS development effort for which we used NI TestStand to create a TPS, CACI developed a nontrivial test capability that worked in a fielded test system in approximately three months. In addition to rapid TPS development, NI TestStand provided several important features such as the ability to capture parametric data to support the creation of test data sheets. NI TestStand also integrated seamlessly with both LabVIEW and LabWindows/CVI, so we could directly call pieces of software developed with these tools without any issues. 

CACI continues to use all three of these software products in conjunction with the CBATS. Typically, we determine whether we use LabVIEW, LabWindows/CVI, or NI TestStand based on the type of item being tested. As a general rule, when the operator is an integral part of the testing, such as when visual feedback or adjustments are required, CACI opts to use LabVIEW. When the end item requires a defined set of electrical inputs and generates measurable outputs that can be collected in a data sheet, and when the testing requires minimal operator input, CACI opts to use NI TestStand alone, or in conjunction with LabWindows/CVI or LabVIEW.

Conclusion

CACI has recognized a pressing need to develop a flexible yet affordable test system for use in maintenance shops to replace legacy test systems that are becoming unsupportable. The result – CBATS – is now a popular and competitively priced test solution for many DoD bench top applications. Other benefits include the common use of instruments for a large number of end items. To date, dozens of test systems containing hundreds of unique parts have now been replaced with either the CBATS 101 or CBATS 201. As an approved member of the DoD Standard Family of Testers (FOT), the CBATS has the potential to continue replacing legacy test systems as well as provide the basis for fulfilling new test requirements.

CACI selected many NI instruments for the core of the CBATS test system based on the relationship with the company and the quality of its products. We also knew that if issues arose, NI engineers would be available to support us. CACI’s relationship with NI has grown to a level of mutual trust as we work together to deliver high-quality, sustainable test solutions at affordable prices.

The mark LabWindows is used under a license from Microsoft Corporation. Windows is a registered trademark of Microsoft Corporation in the United States and other countries.

Author Information:

Paul Pankratz
CACI
Tel: 703-841-7800