Trends in test part 5 – Reconfigurable instrumentation
03 September 2010
In this five-part series, National Instruments draws upon its knowledge and experience of a wide range of industries to identify key technologies impacting test and measurement in 2010. In this final instalment, Jeremy Twaits focuses on the benefits of reconfigurable instrumentation.
Whether adapting to new test requirements or accommodating instrument substitutions during calibration and repair cycles, there are many reasons why a test system may require reconfiguration.
Virtual instruments are inherently reconfigurable, since their functionality is characterised through user-defined software running on a host computer, providing a basic model that is ideal for most modern automated test applications.
Complex devices under test (DUTs), such as RFID tags, microcontrollers and engine control units (ECUs), however, are shifting the need for reconfigurability down to the hardware level. In order to meet strict timing deadlines, such as performing coding/decoding, modulation/demodulation, packing/unpacking and other data intensive tasks within a clock cycle of an RF DUT, intelligence must be deployed onto test hardware. By incorporating an FPGA (Field Programmable Gate Array) inside the instrument, tasks like inline processing and decision-making can be performed at hardware-timed execution speeds, allowing test hardware to meet these complex timing requirements. This, along with their inherent determinism, reliability and parallelism, confirms FPGAs as a powerful platform upon which to base reconfigurable instrumentation.
The true parallelism offered by FPGAs means that different processing operations do not need to compete for the same resources on the chip. Each independent processing task has its own dedicated section, meaning that distinct functions can function autonomously without influence from other logic blocks. The resulting benefit is that as more tasks are added, there is no detrimental impact on other parts of the application.
Whilst FPGAs have been used inside instruments for over a decade, their accessibility to test engineers has tended to be limited. To be useful, in software-defined instrumentation, FPGAs must be programmed by the engineer in software. Traditionally, this meant that FPGA technology was only truly accessible to engineers with a deep understanding of digital hardware design software, such as hardware description language like VHDL or Verilog. It is fair to say that most engineers are not experts in using these tools. High-level design tools, such as LabVIEW, are able to abstract the complexity of digital hardware design, placing the power of FPGAs firmly within the reach of all engineers. New technologies have the ability to convert graphical block diagrams or even C code, into digital hardware circuitry, greatly simplifying the design process.
An example of this comes from Siemens, who used LabVIEW and PCI-based FPGA cards to test tele-protection systems, which play a critical role in isolating faults in power networks, preventing outages and blackouts. FPGAs were used for control and measurement within the system, recording system response within a microsecond resolution.
Martin Brunner from Siemens stated that: “We recommend using LabVIEW for application development as well as for FPGA programming since it does not require additional knowledge in VHDL/FPGA design methods or skills in other programming languages.”
As test engineers continue their quest to reduce test time and system cost, this growing accessibility of FPGAs to all engineers, along with the inexorable rise in DUT complexity, means that reconfigurable instruments will continue to find more mainstream applications. Reconfigurable instruments are not just a trend for 2010, but a trend for the entire decade.
Mike Santori, Business and Technology Fellow at National Instruments, adds: “The ability to customise the measurement hardware itself represents yet another milestone in the path towards a completely software-defined test system. In 10 years, we will wonder how we ever programmed test systems effectively without this capability.”
Time will tell whether this prediction comes to fruition, but what is for sure is that whilst the military and aerospace industries have been early adopters of FPGA-based instrumentation through their synthetic instrumentation initiatives, there is huge potential for telecommunications, automotive, medical and consumer electronics applications too.
Jeremy Twaits is Technical Marketing Engineer, National Instruments UK & Ireland
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