Conformity Magazine - July 2008 - (Page 13)

I n a previous article (see Conformity, February 2008), we described how to select the right chamber for different EMC tests. CISPR standards have evolved at an ever increasing rate since the original publication of that article and, while methods below 1GHz are established, work continues on developing measurement methods above 1 GHz. CISPR is also looking to harmonize CISPR 16 measurement methods between product groups, and this is leading to an increased level of coordination between the committees responsible for the standards. As a consequence, current and future versions of CISPR standards, such as CISPR 11, 14 and 22, may refer to the measurement methods in CISPR 16 rather than write their own, and in fact CISPR 22 already does so. The new proposed multimedia standard CISPR 32 that will replace CISPR 13 and 22 is looking to introduce ideas not yet included in CISPR 16, including the controversial idea of accepting alternative methods. We will discuss the likely impact of all these changes in this article. CISPR 16 Standards Series The IEC manages a number of different EMC standards committees. Emission methods come under CISPR as shown in Table 1, and IEC committees working on immunity methods are grouped under TC 77/SC77B and work on the IEC 61000 series of standards. The CISPR 16 series of publications are basic standards for the measurement of radio disturbance in the frequency range 9kHz - 18GHz. Before 2003, the series of standards was divided into 4 parts, CISPR 16-1, 16-2, 16-3, and 16-4, and totalled 1015 pages. A re-organization took place to divide the series of standards into smaller subject-related publications, so that the basic structure was kept, and new parts designated 16-1-X , 16-2-X, etc., where the x values range from 1-5, as shown in Table 2. This reorganization of the standard in the last five years has seen a huge increase in the workload for CISPR/A. The wide scope of the CISPR 16 standards series as a basic standard means that not all its content is relevant to us in this article. Instead, we will primarily focus on particular parts of 16-1 and 16-2 that concern radiated measurements and anechoic chambers, and their subsequent impact on a number of CISPR product standards. CISPR 16-1-5 [1] Antenna Calibration In order to perform chamber validation, the antennas to be used must be calibrated, and here we need to start with a number of definitions. First, CISPR 16-1-5 defines an antenna calibration test site (CALTS) as an open area test site (OATS) with a tightly specified site attenuation (SA) performance for horizontal electric field polarization only. A CALTS can be used to determine the free space antenna factor (FSAF) of an antenna. CISPR 16-1-5 also defines a reference test site (REFTS) as an OATS with a tightly specified SA performance in horizontal and vertical electric field polarisation. Finally, a COMTS is defined as a compliance test site which is used for the demonstration of product compliance to radiated emission limits. The COMTS will therefore be in our case the anechoic chamber we are validating. The SA measurements of an REFTS are used to compare corresponding SA measurements of a COMTS, in order to evaluate the performance of a COMTS. Alternatively, the measured SA of a COMTS can be compared to theoretical values. The CALTS in CISPR 16-1-5 is validated using calculable dipole antennas which provide an absolute traceable reference to an expected performance based on theory. Close agreement between measurement and theory has been obtained on a number of prime calibration sites worldwide, Sub Committee CISPR A CISPR B CISPR D CISPR F CISPR I Standard CISPR 16 CISPR 11 CISPR 12 and 25 CISPR 14 CISPR 13 and 22 Table 1: CISPR standards and their sub-committees JULy 2008 Conformity 13 http://www.nxtbook.com/nxtbooks/conformity/0208/index.php http://webstore.ansi.org http://webstore.ansi.org

Table of Contents Feed for the Digital Edition of Conformity Magazine - July 2008

Conformity Magazine - July 2008 Contents Editor's Note FCC Adopts 6 Million Dollars in DTV Enforcement Orders Commission Enforcement Bureau Adopts V-Chip Consent Decree FDA Seeks 2 Million Dollars from Medical Device Manufacturer FDA Answers Questions About CFLs and UV Radiation EPA Issues Energy Star Specs for TV, Video Boxes Canada Unveils Sweeping Product Safety Legislation How the Evolution of CISPR Standards Continues to Shape the Requirements for Anechoic Chambers ESD Open Forum Reach Compliance for Non-EU Article Manufacturers The iNARTE Informer Preamplifier Considerations for Emission Measurement Systems Effective Shielding in Medical Electronics Applications Product News Focus On...Power Components Buyer's Guide Updated Standards List for the EU's ATEX Directive EOS/ESD Symposium Set for September CPSC Actions in the News Researchers Work to Develop Non-Flammable Batteries Safety Link Launches Redesigned, Enhanced Web Site IEC Standards Update UL Standards Update Product Reviews Telcordia Standards Update From Our "You Can't Make This Stuff Up" Department Looking Back: Items from Past Issues of Conformity Advertisers

Conformity Magazine - July 2008

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