Software Improves EMC Testing

Electromagnetic compatibility (EMC) test software is a welcome savior now that worldwide EMC regulations are mandatory. It can save time, provide a bounty of information and, in general, go a long way toward reducing the frustration level you may encounter with today’s EMC testing.

Evolution of EMC Test Software

The late ’70s and early ’80s marked the beginning of a new wave of automation for all types of electronic equipment. The GPIB was becoming available in a wide variety of equipment. Personal computers, which made good controllers well suited to EMC automation, also entered the marketplace around this time. And as test equipment was becoming digital, more data and setups could be stored and transferred.

These technologies were the backbone for developing EMC test automation. Interestingly enough, because of the higher emissions generated by digital circuitry, they also were the driving force behind the need for more EMC testing and new regulations. Not only did they provide the means for EMC automation, they also increased the need for it.

For tests such as radiated emissions, EMC test software truly has made a world of difference. Gone is the need to manually set an analyzer or receiver for each portion of the test, record as much data as possible with pencil and paper, and then painstakingly calculate the actual field strength at each frequency using tables of antenna factors, cable loss and pre-amplifier gains. What used to take hours now takes minutes.

Along with the tremendous time savings, a wealth of useful information is provided. Instead of a few data points at the end of a spreadsheet, a curve showing the actual field strength over the entire frequency spectrum now can be displayed on a graph. Getting the whole picture in a graph provides quick insights into the source of emissions which otherwise may have taken hours of analysis to uncover.

Another good example of the efficiency of EMC test software is the radio-frequency field-radiated immunity test. If you have done this test manually, you can attest to the drudgery and frustration of adjusting the frequency control with one hand while trying to maintain a constant field strength by adjusting the generator output with the other, all while watching both the field strength indicator and the EUT. Leveling can now be handled entirely by the controller, leaving you free to concentrate on observing the EUT.

Capabilities

Almost every EMC lab today uses software automation to some degree. Even engineering groups who only make simple measurements with a minimum of equipment find that software automation is cost-effective. For labs dedicated to EMC testing, test software is not only necessary from an efficiency standpoint; some tests today simply couldn’t be run without it.

Most emissions test software today controls the turntable and antenna positioning mast as well as the analyzer or receiver. With the exception of setting up the EUT at the beginning of the test, the entire process of performing a radiated scan can be automated. With one keystroke, the measurement can be made, a plot of the field strength printed, and a table of the worst-case emissions and the respective margins displayed.

Many of the new IEC 1000 series standards have been developed with software capability in mind. The IEC 1000-4-3 RF field immunity test requires measurements of field uniformity and the generation of a leveling file to maintain that uniformity, a task that would be impractical without EMC software.

Many EMC test packages also help generate reports. While some merely provide a table or graph of the results, others enter this information into a report template on a common word-processing application. At the end of the test, you only add or edit minor details and print the report.

The Future of EMC Test Software

EMC test requirements will continue to expand for years to come, and more testing will require more real-time analysis. As a result, new EMC test software should integrate with design and predictive analysis software. Plug-and-play software should be usable with receivers, spectrum analyzers, frequency synthesizers, turntables, masts and whatever other EMC equipment is necessary from most any manufacturer. With these goals in mind, there is an excellent opportunity to further develop EMC test software to enhance EMC design, analysis, testing and prediction. Table 1 lists some of the criteria to consider when selecting an EMC test software package.

About the Authors

Henry Benitez is a NARTE-Certified EMC Engineer at Tektronix and a member of the Information Technology Industries Council ESC-5 EMC Committee. He has a B.S.E.E. degree from the University of Portland. Mr. Benitez has participated as a member on the ANSI U.S. Technical Delegation during direct discussions with representatives of the European Community. Ron Fairley is an EMC Engineer at Tektronix. He has a B.S.E.E degree from Oregon State University. Tektronix, Measurement Business Division, 13500 S.W. Karl Braun Dr., Beaverton, OR 97077, (503) 627-1217.

Table 1

Ease of Use	Is the software easy to use? Is it intuitive or does it require continual reference to the user’s manual? Windows-based software usually provides an interface that is easy to understand and familiar to most users. Non-Windows-based software can be good if designed carefully.
Flexibility	Can the tests be configured to meet your needs or does it only perform predefined tests? Consider variations to your normal test procedures.
Compatibility With Different Equipment and Vendors	Will it work with all your equipment or are you tied to one vendor? Can you upgrade or use alternate equipment when your normal equipment is being calibrated or repaired?
Ability to Control Ancillary Equipment	Can it control other pieces of your test system such as a turntable and mast? The inability to communicate with just one piece of your test system can mean a significant loss of potential efficiency.
Auto Quasi-Peak Capability	Can the software automatically determine radiated or conducted emissions peaks that must be measured with a quasi-peak or average detector to determine compliance? Will it automatically resolve and measure these frequencies? If so, does it do this accurately and thoroughly or is it easily fooled into an erroneous result?
Future Compatibility	Will it support new equipment you purchase or new tests you perform? Can drivers for new equipment be added as they are developed, without an upgrade to the main program?
Report Generation Capability	Does the software create a report complete with EUT information and test results? Can be easily modified? If not, does it provide tables and graphs that can be placed directly in reports without more work or calculations?
Pass/Fail Analysis	Will the software determine pass or fail automatically and report this result?
Direct Loading of Transducer Factors	Can it load antenna factors, preamplifier gains and other information directly from floppy disks generated in a common format?