The Assign Tests and Groups window allows you to change most attributes of any test or group. These attributes include program flow, test parameters, hardware connections and power sequences.
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The main development window allows you to add, replace or delete groups, tests and functions in a test program. It also provides access to all other parts of the development environment, such as Describe UUT-Interface, Describe Connections or Describe Power.
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The Describe UUT Interface Tool allows easy input of data required for switching instruments to the UUT and for creation of the fixture report.
Global competition is forcing companies to streamline their operations to reduce costs. One high-cost operation receiving a lot of attention is test. And test-program generation is at the top of the list for high recurring costs.
Costs have been high because most functional test stations have been custom— either IEEE 488-based rack-and-stack systems or system hot-mockups—and programming tools have not been refined. While software languages are powerful, they are general programming languages developed for a range of engineering applications. They lack the production-focused efficiency and structure required to significantly reduce test programming time and cost while maintaining consistent test results.
Some companies have invested sizable R&D efforts to create a more robust test programming environment for themselves. But they soon discover that new technologies and test problems force never-ending development efforts.
This has led ATE vendors and test-system suppliers to form closer business partnerships with their customers. Many companies buy test solutions from outside vendors, and their test engineers spend most of their time determining the most efficient test strategy. They spend the rest of their time programming the test strategy and debugging the code. But what the test engineer really needs to become more efficient is a test-management software system.
Test-Management Software
A third-party test-management software package brings advantages to the test floor that cannot be realized by in-house test executives. This software combines the elements of production-process management, test-program development, dynamic signal switching and on-line compliance with documentation management specifications. To better understand what this software can offer, let’s examine the major components used in production test:
Test Executives/Flow Control
Most test executives are simple boilerplates in which tests can be inserted to provide simple flow control. This allows the engineer to develop tests in a fashion similar to that of his colleagues. When you compare the programs, they appear to be somewhat similar in structure, making them easier to maintain.
It is more desirable to reuse tests and test functions from test program to test program. In a more sophisticated test executive, a test program can be constructed by simply clicking on test functions listed in a library. Then, those functions can be strung together to form a test, each different test can be strung together to form a test program, and finally the execution order of the tests can be changed and saved to create many test scenarios.
Once a test program is functional, optimizing the execution speed is essential to increase throughput and to reduce the number of test systems needed to support production. Utilities are needed to provide actual test execution times, function call and test overhead. Then, the engineer can pinpoint the areas of the program that need to be optimized to increase throughput.
Signal-Path Programming
For tests and test functions to share a library, the test program’s unique switching must not be part of the test code. Consequently, a separate utility in the test-management software must take care of signal routing.
Most test engineers want the flexibility to connect any measurement resource to any pin of the UUT. They define how the UUT is connected to the switching matrix and how the test instruments are connected to the matrix. This test-interconnection topology allows individual tests within the test program to reference only the UUT signal name and instrument that it needs.
By determining the signal switch path during program execution, test programs are unaffected by wiring changes in the fixture and cabling. So when any wiring changes are made, the engineer only has to make a change in one place.
Datalogging
Test development is only one aspect of a production test operation. Analyzing the test information that is gathered and quickly acting on it result in higher yields and reduced costs. Most test executives do not have datalogging tools, so the test engineer usually has to write some in-line code to capture the desired test data. What you really need is comprehensive datalogging that can be customized to use with an existing quality management system. This allows the test-management software to become an integral part of your production process flow.
Common Operator Interfaces
Most companies have a variety of test systems and it is only natural to want to use the same test-executive software. This allows all operator interfaces to have the same look and feel regardless of whether they are being used for test development or production test. Common operator interfaces across all production test systems allow quicker cross-training of production personnel and reduce learning time for operation of new test systems.
Test-System Security/Administration
A typical test-engineering department has many users, projects, programs and test systems that all require close management attention to ensure efficient operation. System access should be controlled by password login that will allow a variety of system features and modes to be locked out depending on the user’s access level. This ensures the integrity of the system and protects test programs from unauthorized changes.
Keeping track of the calibration status of every instrument in every test system can be tedious. A good test-management software system makes this task easier by tracking the calibration dates of each instrument in the system. Alerting the operator when an instrument is close to its calibration date or preventing any programs from running on a tester that is out of calibration will reduce maintenance cost and improve productivity.
Automatic Generation of Test Reports
Given the time constraints of writing and debugging the program, the documentation of what has been done is typically generated at the very end of the test-development process. Last-minute changes to the software and hardware can sometimes be overlooked and not documented.
Because the test program and wiring information have been entered into the test-management system during integration, the system should be able to generate several reports, such as fixture wiring and test flow. Proper documentation is essential to ensure compliance with documentation management specifications, such as ISO 9000.
In-House vs Third Party
To develop a comprehensive test-management solution in-house is a major commitment of time and engineering resources. Is it good business to produce exactly what you want or to buy a third-party package?
The cost of software development can be more than 10 to 20 work years, which translates into well over a million dollars. Sure, you can cut back on features and capability, but you defeat the purpose of developing your own system. It truly comes down to two questions: what is your core business and can you afford to divert test engineering resources to develop a custom in-house product?
Real-World Application
To help you understand the importance of test-management software, let’s look at an actual VXI system application. When AT&T was developing its new generation of SONET line interface units, the company realized that it would need new functional test equipment. The company wanted more flexibility and capability for production test, so a VXIbus-based tester that used commercially available hardware and software was chosen.
Previously, all of the functional test platforms used in-house software and IEEE 488 instrumentation. The goal was to have a tester platform that supported future production-test applications and improved test throughput.
AT&T defined the following requirements for the new test system:
System software that includes instrumentation drivers, a test executive, datalogging, networking capabilities and system self-test.
Software that conforms to industry or de facto standards.
Easy integration of standard and custom interfaces to control the hardware and software.
A signal-switching matrix to support both electrical and optical signals.
A fixture interface to support a variety of products, both present and future.
A tester platform optimized for production test and throughput.
To fulfill AT&T’s requirements, GenRad’s VXI Extended Architecture (GENEVA) test platform was selected, which included the company’s ENCOMPASS Test Management Software, Tektronix SONET/SDH VXI modules and National Instruments’ LabWindows/CVI software development environment. The instrument drivers complied with the VXIplug&play Systems Alliance standards and with the VISA Transition Library.
Almost all the instruments, interfaces and switches were contained within the VXIbus mainframe. The UUT power supply and optical power meter were IEEE 488 instruments and were mounted in the tester cabinet. Figure 1 is a block diagram of the test system.
The functional test requirements defined by AT&T were:
Optical receiver sensitivity measurements.
Frequency measurements of digital signals.
Microprocessor bus emulation for verification of operational readiness of address/data/control signals.
Verification of various electrical and optical interfaces as well as SONET frame content.
To ensure that the test system was production-ready, AT&T required that it run for several days without any failures. After integration, the tester met all of its functional test requirements. It also reduced functional test times by 50% when compared to comparable circuit cards. The combination of VXI hardware coupled with a commercial test-management software helped create a test system that met the needs of today with expandability for the future.
Summary
A comprehensive test-management system will help you effectively manage your production process, improve the quality and repeatability of your programs, reduce complex branch/flow routines, provide calibration monitoring, establish user privileges, offer data collection and simplify signal path programming. In addition, a variety of software development environments give you a choice of graphical or code-based programming.
Commercially available software allows you to take advantage of these benefits without the expense of development. Now you can focus internal resources on your core business and get your products to market faster.
About the Author
Paul Bennett is a GENEVA Product Marketing Manager at GenRad. He holds a B.S.E.E. degree from the University of New Hampshire and an M.B.A. degree from California Lutheran University. He has been involved in product test for 14 years and with VXI systems for the past six years. GenRad, 300 Baker Ave., Concord, MA 01742-2174, (508) 287-7969.
Copyright 1996 Nelson Publishing Inc.
May 1996