Evaluation Engineering - December 2008 - (Page 19)

ﬂexibility needs. Integration of the various SI hardware pieces and measurement science puts higher expectations on the software used. Use IVI drivers wherever possible to maximize the possibility of interchangeability. You want to be able to use the best tool for the job and integrate your pieces together. • Engineering equivalence is very important if you are swapping hardware or software. For example, one instrument bases its measurement on an input of Start Frequency and an input of Stop Frequency while the next instrument is based on an input of Carrier Frequency and Frequency Span. This is a very simple calculation, but if your TPS is based on one or the other, a simple program needs to be added to ensure engineering equivalence. • Pay attention to different data scaling. Some instruments auto-scale; others require setting the minimum and maximum. Each instrument has different ranges that need to be accounted for in your algorithms. • Watch for different data types. A spectrum analyzer outputs a spectrum value, the translation from time domain to frequency domain being done in ﬁrmware. However, a downconverter may put out a time-based waveform and require a software spectrum waveform calculation separate from the SI down-converter. • Make sure you understand your system I/O. The gain in ﬂexibility now requires more attention to details. In my case, I had a group of instruments connected via LAN that IT would bounce off every 30 minutes for security reasons until I got my own instrument subnet. • Pay attention to cabling and calibration between SI hardware. System calibration and inline corrections between SI hardware are especially tricky with RF signals. In gaining ﬂexibility, ﬁne-tuned signal paths within an integrated instrument now are, in some cases, broken. With different lengths of cabling and quality of cabling, your results may vary. In my experiments, I borrowed a well-used cable that turned out to have an intermittent problem. In another case, moving my SI hardware boxes around in my test area caused a connection to loosen, changing my results. Summary SIs are reconfigurable elemental hardware and software components emphasizing separating individual components at a ﬁner granularity of measurement science. They provide a smaller footprint and greater ﬂexibility over time. accurate results, engineering equivalence of prior solutions, and adequacy for capabilities that were provided in the instrument. These needs will put more importance on integration and measurement science software, whether leveraged from instrument firmware or provided by software vendors or system integrators. References 1. SIWG Meeting #2 Statements and Deﬁnitions, Dec. 11, 2004. 2. Solicitation Number: eCASS-RFIB, Department of the U.S. Navy, May 15, 2008, www.FedBizOpps.gov 3. P1671.2/D9: IEEE Draft Trial-Use Standard for Automatic Test Markup Language (ATML) for Exchanging Automatic Test Equipment and Test Information via XML: Exchanging Instrument Descriptions, April 2008, http://ieeexplore.ieee.org/servlet/ opac?punumber=4497172 4. Stratton, J., CanYou Make One Size Fit All?, Agilent Technologies, ieeexplore. ieee.org/iel5/10700/33790/01609120. pdf?arnumber=1609120 5. Creating an SI With Virtual Instrumentation Technology, Sept. 6, 2006, http://zone.ni.com/devzone/cda/tut/p/ id/3183 6. www.agilent.com/ﬁnd/synthetic Engineering equivalence is very important if you are swapping hardware or software. Standardization work by the IEEE ATML Group and the IVI Foundation Driver Groups will greatly enhance the interoperability of SI components. The IEEE ATML Group is defining an overall description language for all instruments, including SIs, which will facilitate exchange of ATMLprescribed hardware components. The IVI Foundation is developing new IVI classes for an SI down-converter, an SI up-converter, an SI digitizer, and an SI waveform generator that will greatly enhance interoperability. SIs also enable the creation of a wide range of measurement analyses beyond a standard instrument. For instance, a down-converter plus a digitizer plus software can act as a spectrum analyzer, a network analyzer, and a peak power meter. A good implementation of SI requires stable I/O interfaces such as IVI class drivers so older modules could be replaced with the latest technology and protect against obsolescence. IVI drivers are an excellent ﬁt for SIs because the class driver can represent, one-for-one, a large percentage of the SI component’s capability. With greater ﬂexibility comes greater engineering responsibility to ensure all of the components of the test system are properly integrated. This will ensure About the Author Hob Wubbena, a software product marketing manager in the Signal Networks Division at Agilent Technologies, has been with Agilent/ Hewlett-Packard since 1983. Mr. Wubbena is published in more than 13 technical and business publications in the United States, Europe, and Asia and holds three patents relating to displaying instrumentation, system veriﬁcation, and synchronous test. He received an M.B.A. from the University of Denver and a B.S. in engineering from the University of Wisconsin. Agilent Technologies, Signal Networks Division, Electronic Measurements Group, 900 S. Taft Ave., Loveland, CO 80537, 970-679-3363, e-mail: hob_wubbena@agilent.com www. ev alua t ion e n gin e e rin g.com December 2008 • EE • 19 http://www.FedBizOpps.gov http://ieeexplore.ieee.org/servlet/opac?punumber=4497172 http://ieeexplore.ieee.org/iel5/10700/33790/01609120.pdf?arnumber=1609120 http://ieeexplore.ieee.org/iel5/10700/33790/01609120.pdf?arnumber=1609120 http://ieeexplore.ieee.org/iel5/10700/33790/01609120.pdf?arnumber=1609120 http://zone.ni.com/devzone/cda/tut/p/id/3183 http://www.agilent.com/find/synthetic http://www.evaluationengineering.com

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Evaluation Engineering - December 2008 Contents Editorial Product Briefing Test Software C-V Measurements Nanoelectronics Test Product Guide Company Guide Machine Vision EMC Test Index of Advertisers

Evaluation Engineering - December 2008

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