Problem:     Bay Area Rapid Transit had completed a major refurbishment of its transit vehicles. The car builder had delivered test equipment but the transit authority quickly realized that they needed additional capabilities to improve throughput and test coverage. The requirement was for a test system to test the friction brake electronics both at the sub-system level and to provide for card diagnosis and repair. BART mandated that the new test system utilize National Instruments hardware and software to minimize the impact on training since their personnel were already familiar with those tools.

Solution:     Group Alpha reviewed the customer needs and wants and proposed a system built around National Instrument's LabView and Teststand software products. All of the test functions were implemented using LabView and all test sequences were implemented using Teststand. All of the test hardware (excluding the fixture) was built using National Instrument's standard equipment. A custom fixture was developed that provided equipment protection, signal level shifting, and test connections.

The resulting system performs a comprehensive subsystem test to functionally test the braking electronics and to identify problem board assemblies within the braking system. The individual board tests provide functional test, guided fault debug, as well as manually debug capabilities to allow diagnosis done to the problem components. One of the specific customer requests was that the system should provide as much information as possible to the repair technician to eliminate the need for auxiliary documentation. A custom user interface was developed that interfaces to Teststand. It provides enhanced user functions and provides full documentation for the unit under test including: schematics, theory of operation, representative waveforms, and full test documentation. This information is changed based on the context of the test but can be presented at any time by user selection.

The complete system was developed in approximately six months with the machine qualified and on line in less than seven months from the time the order was placed. The resulting system has been well received by both the engineering and technicians at BART and has resulted in the expected improvements in production throughput and test coverage.