Testing

Learn from best practices within the industry, pre-testing considerations, troubleshooting tips, lessons-learned, and problem solving recommendations.

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Independent Labs Provide Value-Added Services

Manufacturers and distributors of electronic and electrical devices are required to meet various Product Safety standards established by the United States, Canada, European Union, and various global agencies. Today manufacturers have multiple options for testing their product to various North American Standards through Nationally Recognized Testing Laboratories (NRTLs), as well as independent value added laboratories that have approvals for NRTL testing under a variety of programs. Good independent labs must be assessed to ISO 17025 for testing laboratories, similar to those requirements found under ISO 9000 requirements for manufacturers.

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Time-Saving Effects of FFT-Based EMI Measurements

In the world of RF and microwave testing, measurements required for EMI are among the most complex and time-consuming since they incorporate a wide array of specific tests that must be performed over an array of frequencies. They typically require not only many hours of test time but even more for configuring and reconfiguring the test set-up.

Fortunately, advances in the signal processing abilities of test equipment have reduced test time over the years. However, the real improvements are the result of enhancement measurement software, greater integration, automation of the test process, and increasing acceptance of time-domain techniques based on Fast Fourier Transform (FFT) for use in preview measurements of the disturbance spectrum, for example. Together they are slowly making the EMC measurement process faster, and more efficient and accurate.

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EMC Test Site Qualifications: Site Voltage Standing Wave Ratio versus Time Domain Reflectometry

Everyone in the EMC business is familiar with the traditional Normalized Site Attenuation test (NSA). However, in February of 2007 CISPR 16-1-4 was published complete with the new Site Voltage Standing Wave Ratio (SVSWR) test. At the time, the American National Standards Institute (ANSI) Accredited Standards Committee (ASC) C63® had developed a draft proposal for C63.4 (Draft 1 - May 20, 2005) called the Time Domain Reflectivity (TDR) measurement. The critical question addressed by this article is which method – SVSWR or TDR - more accurately provides an assessment of the test site. Given the investments companies make in test sites for EMC compatibility, this is key assessment question.

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S-parameter Data Correction Using Time Domain Gating for PCB and Cable Applications

This paper describes how to remove the measurement artifacts caused by discontinuities in high frequency S-parameter data caused by the test connectors on the Printed Circuit Boards (PCBs) and cables. The frequency domain S-parameters are converted to the time domain to get the impulse response. Time domain gating is then used on this impulse response to remove reflections due to end connectors and/or other discontinuities. The gated impulse response is then transformed back to the frequency domain. The final result is a much improved S-parameter data set with unwanted resonance removed, allowing the PCB trace or cable loss to be determined.

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