147. Financial risks and EMC compliance
Silicon Film Technologies, the firm developing a digital ‘film’ that fits in a standard SLR camera body, has suspended operations because of failure to meet EMC standards. “The failure of certification tests in the summer delayed Silicon Film’s anticipated revenues, but development expenses continued,” said Robert Richards, president and CEO of Irvine Sensors, the firm’s largest creditor.
Last week Silicon Film said it had met the FCC emissions requirements but could not conform to the stricter European standards. “We believe at least some of those stricter standards must be met for a successful product launch,” added Richards. If alternative finance is not found, the firm – 51 per cent owned by Irvine Sensors – will go onto liquidation.
(From Electronics Weekly, 19th September 2001, www.electronicsweekly.com.)
148. A make of residual current detector (RCD) tripped out by walkie talkies
A particular make of 30mA RCD units fitted in plastic consumer units in site contractor’s portable cabins would trip when the walkie-talkies used by the contractors were keyed within 1 metre distance. Replacing them with a different make of RCD solved the problem.
(From Chris Byrne of CB Electrical Engineers Ltd.)
149. Numerous stories of external RF sources interfering with aircraft
The penetration of high-intensity radiated fields (HIRF) into conducting enclosures via apertures is an EMI issue that is relevant to all aviation. The stories are numerous, of disrupted communications, disabled navigation equipment, etc., due to the effects of sources external to the aircraft.
(Extracted from “HIRF penetration through apertures: FDTD versus measurements” by Stavros V Georgakopoulos, Craig R Bircher and Constantine A Balanis, IEEE Transactions on EMC, Vol. 43 No. 3 August 2001 page 282.)
150. EMI and the selection of heat-sink thermal gaskets
It should be emphasised that changing heat-sink gasket material as an EMI mitigation strategy is limited to cases in which the heat-sink patch resonance constitutes a significant part of the overall coupling mechanism. Even then, it is necessary to ensure that the shifted patch-resonance does not coincide with a clock harmonic.
Despite these limitations, there are at least two commercial products in which the substitution of one electrically insulating heat sink gasket for another (of the same size but different composition) has resulted in significantly reduced EMI at certain troublesome frequencies. In one of these cases, this reduction was sufficient to allow the product to meet FCC requirements.
(Extracted from “EMI considerations in selecting heat-sink thermal gasket materials”, Huang et al., IEEE Transactions on EMC, Vol. 43 No. 3 August 2001 page 259.)
151. EMI issues loom for future development of single-electron semiconductors
Each year the size of transistors shrinks, thereby improving performance (but not EMC performance! – Editor). Yet, according to Technology Review, transistors must be big enough for electrons to pass through. Preparing for an inevitable impasse, Toshiba has demonstrated a transistor that can turn on and off based on the movement of a single electron. Unlike other quantum-level transistors, the device operates at room temperature. It’s also the first successful hybrid circuit, mixing single-electron transistors with traditional metal-oxide transistors, which are required to boost the weak quantum-level signal.
Chips based on the circuit should offer blazing performance and low power consumption. Before building a full-fledged processor, researchers face challenges such as finding a way to protect the chips from the disrupting effects of stray electromagnetic fields, electrical discharges, and physical movement. Hybrid chips should be available for use by 2010.
(From Electromagnetic News Report, July/August 2001, pages 11-12.)
152. 50 years ago: ignition systems to be suppressed
The Postmaster General’s Advisory Committee on Wireless Interference from Ignition Systems has now presented its report. The Committee devoted its attention in the main to the abatement of interference with the television services of the BBC from ignition systems, including those used in motor vehicles, motor boats, fixed or portable stationary engines, motor mowers, tractors, etc. The Committee’s recommendations are based on the assumption that all reasonable measures will be taken to reduce the susceptibility to interference of receiving installations.
They recommend that ignition equipment, when installed as intended, should not radiated an interference-producing field which exceeds 50 microvolts per metre in the 40-70 megacycles per second frequency band, measured on specified equipment at a point not less than ten metres distant. The committee advise that suppression to this amount can be achieved with negligible effect on the mechanical performance of the engine. In the case of about 60 per cent of existing motor cars the Committee think that the required degree of suppression can be achieved by fitting a single resistor costing about 2s 6d.
(From: Council Notices, The Journal of the IEE, September 1951, www.theiet.org.) (Editor’s note: 2s 6d is equivalent to 12.5p now, or about 18 cents US. Of course in 1951 this amount of money was worth a lot more than it is now.)
The regular “Banana Skins” column was published in the EMC Journal, starting in January 1998. Alan E. Hutley, a prominent member of the electronics community, distinguished publisher of the EMC Journal, founder of the EMCIA EMC Industry Association and the EMCUK Exhibition & Conference, has graciously given his permission for In Compliance to republish this reader-favorite column.
The Banana Skin columns were compiled by Keith Armstrong, of Cherry Clough Consultants Ltd, from items he found in various publications, and anecdotes and links sent in by the many fans
of the column. All of the EMC Journal columns are available at: https://www.emcstandards.co.uk/emi-stories, indexed both by application and type of EM disturbance, and new ones have recently begun being added. Keith has also given his permission for these stories to be shared through In Compliance as a service to the worldwide EMC community.
We are proud to carry on the tradition of sharing Banana Skins for the purpose of promoting education for EMI/EMC engineers.
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