The Automated Test Blog

As I stated in an earlier blog post, I’m planning to discuss one of five industry trends per blog entry over the next few weeks. My 3^rd trend is:

Growing Popularity of FPGA-Enabled Instrumentation
Another area experiencing rapid expansion in the test industry is the increase in system-level tools for field-programmable gate arrays (FPGAs). FPGAs are powerful because they are inherently parallel, deterministic, and reliable and can be defined and reconfigured in software. While FPGAs are used inside many embedded designs, and even standalone instruments, users are not typically given access to reprogram them. More manufacturers are beginning to include open FPGAs on modular instruments and are giving test engineers the means in software to reprogram them according to their requirements. With this capability, test engineers can embed a custom algorithm into the device to perform in-line processing inside the FPGA or emulate part of the system that requires a real-time response. Historically, most test engineers do not have expertise to program FPGAs because they familiarity with hardware description languages like Verilog or VHDL which use low-level syntax to describe hardware behavior. New system-level tools are emerging that provide test engineers with the ability to rapidly configure FPGAs without writing low-level HDL code. LabVIEW, for example, can target onboard FPGAs and synthesize the necessary hardware directly from a graphical LabVIEW program, dramatically reducing the complexity of the code development. I’ve been amazed at the things our customers, who are often domain exprerts, but not experts in hardware design, have been able to accomplish with LabVIEW FPGA.  Examples include testing RFID devices performing bit-error-rate testing (BERT) of military communication protocols.

As I stated in my last blog, I’m planning to discuss one trend per blog entry over the next few weeks. The second trend in Test and Measurement is:

Growth of Software-Defined Instrumentation

One issue facing test engineers is that test instrumentation is not updated as rapidly as the devices being tested. The functionality of these complex devices is being defined by the software embedded in them, such as the Apple iPhone, which gives design engineers the ability to add features faster than ever before. This is increasingly challenging for many test engineers because most stand-alone instruments often lack the measurement capabilities of the most recent standards due to the fixed user interface and firmware that must be developed and embedded in them.
Thus, test engineers are turning to a software-defined approach to instrumentation which gives them the ability to quickly customize their measurement algorithms and user interfaces to meet specific application needs and integrate testing directly into the design process, further reducing development time. PXI is the example of a widely used software-defined instrumentation standard for building modular, reconfigurable high-performance automated test systems.

Kiran Unni, Frost & Sullivan Measurement & Instrumentation research manager, recently confirmed that PXI is influencing this trend when she stated, “The adoption of tools such as PXI is an indicator that companies recognize the benefits of moving toward software-defined instruments. The savings being realized in capital equipment, system development and improvements in system efficiency all contribute to reducing the per-unit cost of test, directly influencing the bottom line.”

One the biggest signs of success factors of PXI has been the increased adoption by major test and measurement vendors. Even though at times they have been hesitant to wholeheartedly support the PXI standard, Agilent, has several product lines in PXI:

•  A line of PXI-based high performance signal generators (N6030A)
• PXI digitizer modules, from their acquisition of Acqiris
• PXI Optical test instruments, form their acquisition of PXIT

Last week, Agilent released new PXI modules in their optical test product line. Their press release notes that the modules offer their customers “a smaller, faster, more cost-effective solution” – precisely the primary benefits of the PXI platform.

I’d like to clarify the difference between these two terms as I have found that there is very often confusion between them. The distinction is entirely in the software model and the programmability of software-based analysis by the instrument user. A Virtual Instrument’s primary programming model is to present raw data to the user for customized measurements. A Traditional Instrument’s primary programming model is to present vendor-defined measurements to the user.

What about Standalone Instruments versus Modular Instruments? This is a question of form-factor, not software, and is therefore entirely orthogonal to whether the instrument is virtual or traditional. A standalone instrument can indeed be used as a virtual instrument. An example is a standalone oscilloscope that is automated to create custom measurements in software. Similarly, it is possible for a modular instrument to present only a traditional use model to the user; VXI instruments, for example, were most often vendor-defined instrument repackaged in a modular form factor.

While the definition of virtual instruments and modular instruments is orthogonal, it is true that many modular instrument standards lend themselves to building virtual instrumentation systems. In order to effectively perform user-defined analysis on a signal, the user must have access to the raw data from the instrument’s acquisition. For high-speed measurements, this requires transferring many megabytes of data from the instrument to a processor to be analyzed in software. High-speed interface buses such as PCI Express, which can transfer data at up to 4 Gigabytes/s, are well-suited to this application. Instrumentation standards such as PXI combine high-speed buses and upgradeable PC-based processors, making it an ideal platform for virtual instrumentation systems.