Conformity Magazine - October 2008 - (Page 51)

continuous frequency sweeping and amplitude leveling, or it can be done digitally. If it is done digitally, the settling characteristics of the signal generator’s output are important in the delivery of a reliable test—large settling transients can cause temporarily large signals which may lead to false test failures. Test Facilities: Weather Protected and Anechoic Radiated interference and immunity measurements have to take place somewhere. For interference measurements, the “gold standard” is the OATS or open area test site. For reasons of weather protection and security, this usually means a “weather protected site,” which requires a building that produces minimal deviations from the ideal situation of open space over a large ground plane. For this to occur, there can’t be any large reflecting objects above the ground plane, which in turn requires that the protective enclosure be both insulating and electrically thin (fractional wavelength thickness). A number of manufacturers offer lightweight, prefabricated plastic and foam buildings reinforced by composite beams that meet the bill. Fabric-walled enclosures—tents and air buildings—also work very well. Standard stud and dry-wall construction is more problematic because of the thickness of the walls and the multiple reflections from the outer and inner walls. These materials can also absorb water from the air and will present different RF characteristics at different humidity levels. This effect can be particularly difficult to characterize and makes repeatability of measurements very difficult. However, regardless of type, the real test is an ANSI/CISPRcompliant site attenuation test on the completed installation. If the ambient signal level in an area is too high for measurement, an OATS won’t do. This is also the case for radiated immunity, but for a different reason; the strong signals generated during an immunity test must be contained to avoid interference with authorized communications. The open area test site has to be moved indoors, into an anechoic chamber. Anechoic chambers have come a long way in terms of cost and size with the introduction of ferrite tiles in the past decade or so. Before the advent of ferrite tiles, anechoic chambers were screen rooms lined with conductive pyramidal absorbers. These absorbers work well so long as they are a significant fraction of a wavelength long. In practice, that used to mean that full-range chambers capable of being used at 30 MHz required 6 to 8 foot cones, and a very large surrounding shielded structure. With ferrite tile absorbers, much smaller chambers are possible because of the reduced wall thickness. A ferrite tile lining adds less than an inch to the chamber wall thickness, while a wide range ferrite/cone combination will be less than a foot thick. For combination absorbers, the ferrite does the work at the lower frequencies, and the absorbing cones take over at the high end. DAMPED OSCILLATORY WAVES – Scalable Solutions to IEC61000-4-18, 60255 series, & ANSI / IEEE C37.90 on Power and I/O lines. Primary unit provides 100 kHz and 1 MHz. Extension adds 3, 10, 30 MHz at any time. Models MIG-OS-OS1 or MIG0603OSI. HARMONICS & FLICKER - Total solution. Simple to use. Complies with 61000-3-2 Eds. 1, 2, 3 and 61000-3-3. Report with tabular and graphic data including new 200% of limit analysis, average and maximum harmonics as a percentage of limits. Model HAR1000. ESD/EFT/SURGE/DIPS/MAG – Integrated solutions for full compliance configurations to IEC Basic Standards. Available SURGE waveforms include Combination, Ring, 10/700 waves at 4kV and 6kV plus ability to couple all phases & neutral to ground as specified in ANSI/IEEE C62.41. Model TRA2000 series. CE Mark Test Solutions Look to HVT for turn key transient test solutions meeting the latest specifications. User Friendly, Repeatable, Reliable. Damped Oscillatory Wave Harmonics & Flicker ESD/EFT/SURGE/DIPS/MAG IEC 61000-4-18, 60255; ANSI/IEEE C37.90.1 IEC 61000-3-2, -3; IEC61000-4-7, -13, -14, -17, -28 IEC 61000-4-2, -4, -5, -8, -9, -11, -12, -16, -29; ITU-T K.44; ANSI/IEEE C37.90; C62.41 Contact us today to add some real Firepower to your test equipment arsenal. Tel: 703-365-2330 • www.hvtechnologies.com e-mail:emcsales@hvtechnologies.com http://www.hvtechnologies.com http://www.hvtechnologies.com

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

Conformity Magazine - October 2008 Contents Editor's Note FCC Releases Annual Report on National Do-Not-Call Registry Commission Cracks Down (for the Fourth Time!) On Junk Fax Marketer FCC Releases Quarterly Reports on Consumer Inquiries and Complaints Greenpeace Ranks Electronics Manufacturers Standards List For The EU’s Energy Consumption Directive Published EU Commission Publishes Standards List for Directives on Pressure Equipment, Pressure Vessels Standards List for the EU’s Medical Devices Directive Available The IEEE Product Safety Engineering Society: The First Five Years ESD Open Forum Improving Election Security and Accuracy: The Future of Voting System Certification Conformity Assessment and Accreditation: Their Role in the Global Market Design Issues in Extreme EMC Environment Focus On... Test Equipment Buyers Guide Product News Updated Standards List for EU Directive on Active Implantable Medical Devices FDA Warns of Effects from CT Scans on Electronic Medical Devices FDA Provides Report Card on Its PMA Review Process CPSC Releases Import Safety Strategy Other CPSC Actions in the News IEC Standards Update Product Reviews UL Standards Update Telcordia Standards Update From Our “You Can’t Make This Stuff Up” Department Looking Back: Items from Past Issues of Conformity Advertisers

Conformity Magazine - October 2008

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