The nine tips below will help engineers get the most for their test system money and will enhance their ability to reuse existing hardware and software. All of the tips involve thinking ahead and developing a test system plan that incorporates reuse strategies. As the cost to develop test applications increases, companies demand their design teams and test engineers to cut expenses. Reuse of existing hardware and software will help.
Avoid development tool obsolescence Engineers should think of their
software development tools as a "free ticket" to software reuse. Using a
programming language and software tools that will remain in use—and that
vendors will support—for many years helps guard against obsolescence.
Engineers want a software development "environment" to exist for their test
system's lifetime—often a decade or more. That doesn't happen often, though.
Recently, Microsoft shifted its emphasis from tools, such as Visual Basic 6,
to Visual Studio .NET. That move will leave many VB6 developers high and dry.
The .NET tools may last for five or six years. But who knows? Engineers should
adopt tools that offer longevity.
Integrate design and test tools Seek software tools engineers can apply
equally well in a development lab or on a production line. When design
engineers and test engineers define their test software needs in parallel,
they can develop a common test strategy that uses one set of software tools.
In addition to saving time and money, using one test development tool includes
hidden benefits. First, design and test engineers can use each other's code.
Second, design engineers can help troubleshoot problems in production, and
test engineers can assist design engineers to ensure sufficient—but not
excessive—production test coverage during product design.
Choose easy-to-use tools Software development tools should be easy to
use, even for novices or engineers who use the tools infrequently. These
latter users should not have to relearn menu choices and other operational
details to set up test applications. Ease of use encompasses the "connection"
of application software to test-and-measurement hardware. Tools should
simplify the configuration of hardware and make it easy for engineers to
transfer data to and from data acquisition modules, digital I/O boards, signal
generators, and so on. And drivers should shield engineers and users from
Develop reusable modules Mention reuse of software and most
developers think only of standard, proven code they can insert in a program as
needed. But software reuse extends farther. Developers interested in
maximizing software reuse should use software tools that produce "modules"
that can operate in two ways. First, they can run on their own to test a
specific function on a device under test (DUT). Second, modules should
operate—without modification—within a larger test management program. Not all
software tools produce reusable modules of this type.
Employ test management software Test management software, also known
as a test executive, handles system-level tasks, such as powering a DUT,
getting the DUT to a specific state, and reporting test results. This
overarching test management software controls and "connects" the modules that
perform specific tests on the DUT. Separating management and test functions
makes it easy to change and reuse individual tests. Combining management and
test routines in a single, inflexible program can force software developers to
dig through lots of code to gain access to the software for individual tests.
Adapt to new buses Engineers must keep an eye on new
technologies, such as the LAN eXtensions for Instrumentation (LXI) that may
make older buses obsolete. By configuring test systems to use the Virtual
Instrument System Architecture (VISA) specification and Interchangeable
Virtual Instrument (IVI) drivers, developers can insulate themselves—and
users—from bus changes. Thus, software can control instruments regardless of
the hardware bus that connects them to a host controller. And, in most cases,
adhering to IVI-driver and VISA specs means adopting a new bus requires little
or no change to application code. Move a DMM from an IEEE 488 bus to an
Ethernet cable, for example, and the DMM and the application will continue to
operate properly. Thus, engineers can reuse instruments and software even as
bus technologies change.
Rely on standard hardware The use of standard hardware increases the reuse possibilities of test systems. Because vendors have invested a great deal in a broad offering of hardware based on USB, PXI, IEEE 488, and other buses, engineers can count on long-term support. So, as testing needs change, engineers can count on a wide array of instrument and control hardware that will keep their test systems up to date. Reuse involves changing hardware functions instead of building a new test system. The PXI bus, in particular, builds on the Compact PCI-bus spec, so in addition to test instruments, developers can buy PXI motion and vision controllers, and many other special-purpose cards. Longevity has its limits,
though. Because the VXI-bus community focused solely on test applications, the
market stayed small. Today, few engineers base new test systems on this bus.
But the VXI bus continues to find use in test systems, particularly those
employed by the military.
Mix and match test equipment To maximize the potential for
hardware reuse, design a test system that will accommodate a variety of
instruments and buses. Then, older—but still useful—instruments can quickly
drop into a system. It's easier to use existing test instruments than to get
approval for a capital equipment purchase.
Seek multifunction equipment A test instrument or module that can solve several problems helps designers reuse hardware in new test systems. A switch card, for example, supplies a matrix of contacts. Cards with a fixed matrix adapt poorly to changing test needs. On the other hand, a card that will change its switch configuration under software control can operate as, say, a 4 × 64-switch matrix today, or as a 16×16 matrix tomorrow. Thus, one card provides many switch configurations, which makes it easy to reuse, as test needs change. Measuring instruments also combine functions so one box or card will measure current, voltage, temperature, inductance, and capacitance, and other quantities, depending on the code that controls it. That capability lets engineers reuse an instrument in a new test system, or they can extend the capabilities of an existing system at no extra cost.
Wired: Test systems usually combine rack-and-stack
instruments, such as the LeCroy oscilloscope, bus-based instruments,
specifically the PXI chassis, and custom equipment. A conscious reuse
strategy extends the lifetime and reduces the costs of test
Safety Integrity Level compliance — a global standard for the safety level of control systems — is a key method manufacturers can use to ensure customers and partners that their products’ control systems are in top working order.
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