A clear understanding of OSHA safety requirements and the objectives of the NRTL program can render the testing and approval process easier for electronics manufacturers. Regan Arndt, TÜV SÜD America, San Diego, California, USA INTRODUCTION The Occupational Safety and Health Administration (OSHA), an arm of the U.S. Department of Labor, is the primary federal agency … [Read more...]
Regulatory Agencies Upping Enforcement Actions
The FCC carries out random audits of products that have received recent TCB grants. David A. Case NCE, NCT, Cisco, Richfield, Ohio, USA The question that occasionally comes up, generally from someone not familiar with compliance, goes something like, “What will the Federal Communications Commission do to us if we are non-compliant, or how will the agency know?” Both questions … [Read more...]
Increasing Design Flexibility for Board-Level Shielding
Today's consumers want electronic devices in all shapes and sizes, a demand that can dictate the enclosure design and board shape. David P. Donaldson, Applications Engineer, W.L. Gore & Associates, Inc., Newark, DE, USA As electronic devices are getting smaller and as consumers are demanding more features, designing printed circuit boards (PCBs) is becoming increasingly … [Read more...]
The Institute of Engineering and Technology’s New Guide on EMC for Functional Safety
A brief introduction... Keith Armstrong, Cherry Clough Consultants, Brockton, Stafford, UK This new publication (August 2008) EMC for Functional Safety published by the Institute of Engineering and Technology (IET) replaces the IEE’s 2000 edition. The Guide comprehensively describes practical and cost-effective procedures that can be utilized by both management and … [Read more...]
Inrush Current in DC-DC Converters
Some applications may require limiting the inrush spike into the input capacitors. Steve Butler and Jeremy Ferrell, VPT, Inc., Blacksburg, Virginia, USA BACKGROUND Inrush current is the spike of current drawn by a power supply when it is turned on. A typical power system is shown in Figure 1. The input EMI filter will include some capacitance connected across the input … [Read more...]
Solving the Galvanic Corrosion Issue in EMI Shielding
Tungsten carbide/aluminum composite particles inhibit galvanic corrosion of aluminum. Harry Fuerhaupter, Potters Industries, Inc. ABSTRACT An ongoing issue in the design of reliable EMC shielding is galvanic corrosion of aluminum. How can an aluminum frame be protected from galvanic corrosion if it contacts an EMI gasket containing non-aluminum particles? Chromate conversion … [Read more...]
Crucial RF Shielding Selection Considerations
Gary Fenical Laird Technologies INTRODUCTION Designers must attenuate RF signals for various reasons. Since a product cannot be legally marketed unless it meets EMC requirements, designers must curtail RF signals above a certain limit. It is important to consider RF shielding materials at the beginning of a design project because choosing the correct kind of shielding upfront … [Read more...]
Understanding Shielding Effectiveness of Materials and Measurements in the Near-Field and Far-Field
When we treat the shielding effectiveness measurement with a uniform field, the results are similar for both near and far fields. Kermit O. Phipps and Philip F. Keebler EPRI EMC Laboratory, Knoxville, TN, USA INTRODUCTION Traditionally Schelkunoff’s shielding effectiveness equation is used universally in teaching and practice throughout the EMC community as a whole. In this … [Read more...]
Magnetic Shielding Design for Manufacturing
Sensitive electronic devices require protection from radiating magnetic fields. David Grilli Magnetic Shield Corporation, Bensenville, IL, USA Magnetic shielding for static and low frequency (<100 kHz), time-varying magnetic fields is accomplished by containing a specific device or item within a sheet metal enclosure of high permeability material. Typically, a sensitive … [Read more...]
Designing an RF Shielded Enclosure
Ron Brewer EMC/ESD Consultant Shielding has been with us a long long time. Early AM radios had shielded RF and IF transformers, shielded electron tubes, and compartmentalized shielded chassis. These shields were necessary to prevent RF pickup, feedback, and oscillation by the electron tubes, radiation from the local oscillator, RF contamination of the IF strip, and crosstalk … [Read more...]
