Design Con 2015

Modular framework speeds bench instrument evolution

-February 11, 2013

Rapid evolution in standards such as wireless telephony is placing unprecedented pressure on the test instrument industry to quickly create new instruments to support product design, certification, production, and field test. While custom instruments assembled using open modular frameworks can help address these needs, especially in the design laboratory, they are challenging to apply in field and production use. Instrument manufacturers can address these challenges by taking advantage of open modular standards to create in-house hardware as well as software synthetic instrument frameworks for new instrument designs.

Test engineers have widely embraced modular instrumentation architectures for their cost benefits and design flexibility. In this era of rapidly-evolving technologies and standards, the ability to quickly create instruments that address new test requirements is becoming essential. Yet the same flexibility in modular architectures that allows such customization creates challenges in many applications. Field, compliance, and production testing, for instance, benefit greatly from the traceability and ease-of-use that comes with traditional vendor-configured equipment functionality. Unfortunately, traditional vendor approaches to creating such instruments are slow in reacting to changes in functional requirements.

The synthetic test instrument design approach provides vendors with a means of combining the rapid adaptability of modular instruments with the configuration control and turn-key operation of traditional instruments. It allows equipment vendors to quickly respond to shifting standards with product variations and updates as well as create cost-effective, semi-custom test instruments for major customers – while at the same time providing the configuration and functional stability desired by engineers who want to do testing, not configure equipment.

Simply building test equipment using one of the modular standards is not a full solution, however. For one thing, no one standard addresses the full range of test environments efficiently. Standard modules and chassis sizes are often too big or too small, and power and bus performance limits can be a drawback for some applications. Also, modular test architectures lag in high-performance mesh multiprocessing support while high performance modular computing standards lack the synchronization and triggering structures needed for test.

Fortunately, equipment vendors need not be restricted to a single modular standard when creating an in-house framework. Multiple standards can be combined as long as they share a high-bandwidth means of exchanging data and commands. PXI Express and ATCA, for example, have PCI Express bus connectivity in common, which allows them to work together in a single hybrid system. This mutual connectivity is already being exploited in the emerging AXIe modular test standard.

Proprietary yet standards-based
A proprietary hybrid of modular standards may seem an oxymoron at first, but there are many advantages to both the instrument vendor and end users in adopting such an approach. One is that, by mixing standard architectures, the vendor’s framework can benefit from the strengths of one architecture to overcome weaknesses in another. Processing power in a PXI system controller, for instance, is often a generation behind what is available in MicroTCA and cannot support mesh multi-computing. However, blending the two allows a framework to offer the instrument functions of PXI with far greater processing power than PXI alone can provide.

The mixing of standards in a proprietary framework also provides an opportunity to bypass some of the form factor restrictions of the standards. A low power PXI module can fit into a battery powered handheld instrument, for example, since the vendor controls integration within the proprietary framework and can manage any non-compliant specifications. This freedom allows a vendor to create a wider range of instruments based on their common framework than is possible simply using the standards alone.

One of the primary advantages is a reduction in the effort needed to develop targeted instrumentation. The adoption of standard architectures into their framework gives vendors access to the multitude of modules available under the standards. This can significantly cut the time and effort needed to create a new instrument targeting an emerging application or to modify an existing instrument to upgrade performance. With a properly designed framework, vendors are able to assemble the foundation structure for a new instrument or upgrade an existing instrument using available modules that best match the target requirements.

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