Conformity Magazine - September 2007 - (Page 25)

T he basic standard for system-level electrostatic discharge (ESD) immunity testing of electrical and electronic equipment, IEC 61000-4-2, has remained essentially unchanged for more than 10 years. Over this time, in-depth understanding of the benefits of this standard, as well as areas where enhancements could be made, have been developed across a wide section of the industry segments in which this standard is applied. The International Electrotechnical Commission (IEC) is engaged in an active maintenance project to address industry concerns and to update this important basic standard. This article will briefly discuss the essential concepts of system-level ESD immunity testing according to IEC 61000-4-2 and provide an insider’s view on the maintenance project to revise the standard. It describes the concerns being addressed; the process employed for maintenance revision, including determining what elements of the standard would and would not be considered for change; the initial modification proposed; the changes in the current proposal, and; the rationale for why some elements are not being changed. Some ideas for potential future improvement, and what needs to happen for those to become realized, are also briefly introduced. IEC 61000-4-2 System-level ESD immunity testing consists of injecting static electricity discharges into the exposed exterior surfaces of complete electronic equipment that is set up and operating as it would under normal end-user conditions. The equipment thus being tested (often called the equipment under test, or EUT) is monitored for any malfunctions or deviations from its expected operation. Malfunctions can be classified into three general categories: • Temporary errors that are automatically corrected by the EUT or its operating software; • Temporary errors that require some intervention by the operator to recover to normal operation; and • Permanent damage that requires repairing or replacing part or all of the EUT. Depending on the type of equipment being tested, some of these failure categories may be acceptable during testing. The system-level ESD immunity test requirement for many types of equipment is based on IEC 61000-4-2 [1]. This standard is considered a basic standard. It describes requirements for the basic elements of the test, including test equipment used for the test, the test setup, how to perform the test, general description of the test, and test levels. As a basic standard, IEC 61000-4-2 does not include specific test limits or performance criteria. These last two elements are determined by the particular product or product family standard that applies to the type of equipment being tested. The test equipment for this test is an ESD generator to simulate discharges from a person with an intervening piece of metal hand in the hand. The generator is to be capable of creating a current pulse meeting the criteria shown in Table 1 and of the approximate shape shown in Figure 1. The simplified model of the ESD generator is shown in Figure 2. In its simplest form, the generator consists of a capacitance that is charged to the test voltage, a discharge resistance through which the stored energy is discharged, an internal switch, and a metallic electrode or tip that contacts the surface receiving the discharge. The test generator needs to be capable of operating in two discharge modes: air discharge mode, in which the electrode is charged and then brought into contact with the EUT and the discharge occurs with an arc between the electrode and surface receiving the discharge; and contact discharge mode, in which the uncharged electrode is placed in contact with the surface receiving the discharge, and then the internal switch is closed to complete the discharge circuit. The EUT is configured and set up in a manner consistent with typical use. To assist in obtaining repeatable test results, the EUT is placed above a metallic ground reference plane and insulated from it to prevent unintended direct electrical connection to it. Equipment that is normally installed on a desk or table is placed above a coupling plane that is located 0.8 m above the ground reference plane. This table-top SEPTEMBER 2007 CONFORMITY 25 http://www.monroe-electronics.com http://www.monroe-electronics.com

Table of Contents Feed for the Digital Edition of Conformity Magazine - September 2007

Contents Editor’s Note FCC Extends Disability Access Requirements to VOIP Commission Fines Importer $3 Million Over Non-Compliant TVs FCC Gets Tough on Retailers Over Analog TV Tuner Labeling Analog Cellular Service Sunset Date Reaffirmed Commission Adopts Recommendations of Katrina Panel Free-Space Antenna Factors Through the Use of Time-Domain Signal Processing Editorial Correction ESD Open Forum An Update on Revisions to IEC 61000-4-2, the Basic Standard on ESD Practical Advice for Meeting the DFS Testing Requirements of the FCC The EMC Impact of Embedded Software ESD Design Buyer's Guide Tate Renominated to the FCC EPA Releases Report on U.S. Electronic Waste Additional Standards For The EU’s Toy Directive Medical Device Manufacturer Enters Consent Order Updated Guidance Document on Laser Products Issued FDA Offers Advice on Defective Heating Pads CPSC Issues China Product Safety Program Report Other CPSC Actions In The News IEC Standards Update Product Reviews Product News UL Standards Update From Our “You Can’t Make This Stuff Up” Department Looking Back: Items from Past Issues of Conformity Advertisers

Conformity Magazine - September 2007

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