产品设计师的EMC指南：第四版

需积分: 10 31 浏览量更新于2024-07-27 1 收藏 7.27MB PDF 举报

"EMC for Product Designers, Fourth Edition" 是一本由Tim Williams撰写的关于电磁兼容（EMC）设计的经典著作，旨在帮助产品设计师在设计过程中融入EMC原则，以符合最新的EMC指令要求，避免额外的成本和性能损失，同时满足特定标准，提升产品的整体质量。这本书的第四版不仅涵盖了最新的法律要求，而且根据EMC合规性和产品设计的最佳实践进行了全面更新。新增了对R&TTE、汽车EMC指令以及军事航空航天标准DEF STAN 59-41和DO160E的讨论，还特别加入了一个关于系统EMC的新章节，并通过案例研究展示EMC产品设计的实际应用。 Tim Williams是一位拥有25年电子设计工程经验的专业人士，他对EMC指令及其相关标准的发展有着深入的跟踪观察。目前，他经营自己的咨询公司，专注于EMC设计和测试建议及培训。本书详细讲解了以下关键知识点： 1. **EMC基础**：介绍电磁兼容的基本概念，包括电磁干扰（EMI）和电磁敏感度（EMS），以及它们如何影响设备的正常运行。 2. **EMC指令**：详细阐述最新EMC指令的要求，指导读者理解并满足这些法规标准。 3. **设计过程中的EMC考虑**：提供如何在产品设计早期阶段就考虑到EMC问题的方法，以降低后续修改的成本。 4. **R&TTE和汽车EMC指令**：针对无线通信和交通电子设备的特殊EMC要求，帮助设计者遵循这些特定领域的规定。 5. **DEF STAN 59-41和DO160E**：解释军事和航空航天行业的EMC标准，对于相关领域的设计师尤其重要。 6. **系统EMC**：新增章节探讨系统级别的EMC问题，包括系统间的互操作性和整体系统性能的影响。 7. **最佳实践**：介绍当前业界认可的EMC设计和测试方法，确保产品达到最佳的EMC性能。 8. **案例研究**：通过真实案例分析，展示如何将EMC设计原则应用于实际产品开发中，提供实践经验。 9. **许可和版权**：强调了内容的版权保护，以及如何合法获取和使用出版物内容的详细信息。这本书对于电子工程师、产品设计师以及从事EMC相关工作的专业人士来说，是一本不可或缺的参考书，它提供了丰富的理论知识和实用技巧，有助于读者在设计过程中有效地解决EMC问题。

Introduction 1

Chapter 1

Introduction

1.1 What is EMC?

Electromagnetic interference (EMI) is a serious and increasing form of environmental

pollution. Its effects range from minor annoyances due to crackles on broadcast

reception, to potentially fatal accidents due to corruption of safety-critical control

systems. Various forms of EMI may cause electrical and electronic malfunctions, can

prevent the proper use of the radio frequency spectrum, can ignite flammable or other

hazardous atmospheres, and may even have a direct effect on human tissue. As

electronic systems penetrate more deeply into all aspects of society, so both the

potential for interference effects and the potential for serious EMI-induced incidents

increases.

Electromagnetic compatibility (EMC), then, is the absence of effects due to EMI.

The definition of EMC, as it appears in the International Electrotechnical Vocabulary

[152], is:

The ability of a device, equipment or system to function satisfactorily in its electromagnetic

environment without introducing intolerable electromagnetic disturbance to anything in that

environment.

Some reported examples of electromagnetic incompatibility are:

• in Norfolk, various makes of car would “go crazy” when they passed a

particular air defence radar installation – dashboard indicators dropping to

zero or maximum, lights and engines cutting out;

• on one type of car, the central door locking and electric sunroof would

operate when the car’s mobile transmitter was used;

• new electronic push-button telephones installed near the Brookmans Park

medium wave transmitter in North London were constantly afflicted with

BBC radio programmes;

• interference to aeronautical safety communications at a US airport was

traced to an electronic cash register a mile away;

• the instrument panel of a well-known airliner was said to carry the warning

“ignore all instruments while transmitting HF”;

• electronic point-of-sale units used in shoe, clothing and optician shops

(where thick carpets and nylon-coated assistants were common) would

experience lock up, false data and uncontrolled drawer openings;

• when a piezo-electric cigarette lighter was lit near the cabinet of a car park

barrier control box, the radiated pulse caused the barrier to open and drivers

were able to park free of charge;

2 EMC for Product Designers

• lowering the pantographs of electric locomotives at British Rail’s Liverpool

Street station interfered with newly installed signalling control equipment,

causing the signals to “fail safe” to red;

• a digital TV set-top box initiated an air–sea rescue operation in Portsmouth

harbour by creating an emission on the distress frequency;

• two Navy warships nearly collided when the radar transmissions of the

frigate HMAS Anzac disabled the steering of the minehunter HMAS Huon,

Huon passing ahead of Anzac “at close range”.

Many other examples have been collected over the years; the “Banana Skins” column

in the EMC Journal, collated by Keith Armstrong, is a fruitful source, and the EMC

group of the former UK Radiocommunications Agency commissioned an EMC

Awareness web page introducing the subject [203], which also contains a number of

examples. Here are a few issues in more detail.

1.1.1 Portable electronic devices in aircraft

Mobile cellular telephones are rapidly establishing themselves, through their sheer

proliferation, as a serious EMC threat. Passengers boarding civil airliners are now

familiar with the announcement that the use of such devices is not permitted on board.

They may be less familiar with why this is regarded as necessary. The IFALPA

International Quarterly Review reported 97 EMI-related events due to passenger

“carry-on” electronic devices since 1983. To quote the Review:

... By 1990, the number of people boarding aeroplanes with electronic devices had grown

significantly and the low-voltage operation of modern aircraft digital electronics were

potentially more susceptible to EMI.

A look at the data during the last ten years indicates that the most likely time to experience EMI

emissions is during cruise flight. This may be misleading, however. During the last three years,

43% of the reported events occurred in cruise flight while an almost equal percentage of events

occurred in the climb and approach phases.

Of particular note: during the last three years the number of events relating to computers,

compact disc players, and phones has dramatically increased and these devices have been found

to more likely cause interference with systems which control the flight of the aircraft.

Recognising an apparent instrument or autopilot malfunction to be EMI related may be difficult

or impossible in many situations. In some reported events the aircraft was off course but

indications in the cockpit displayed on course. Air traffic controllers had to bring the course

deviations to the attention of the crews. It is believed that there are EMI events happening that

are not recognised as related to EMI and therefore not reported.

Particular points noted by the Review were that:

• events are on the rise;

• all phases of flight are exposed (not just cruise);

• many devices may cause EMI (phones, computers, CD players, video

cameras, stereos);

• often there will be more than one device on a flight;

• passengers will turn on a device even after being told to turn it off

†

;

• passengers will conceal usage of some devices (phones, computers);

• passengers will turn devices on just after take-off and just prior to landing;

• phones are a critical problem;

Introduction 3

• specific device type and location should be recorded and reported by the

crew;

• when the emitting EMI device is shut off, the aircraft systems return to

normal operation (in the case of positioning errors a course change may be

necessary);

• flight attendants should be briefed to recognize possible EMI devices.

In 2000, the Civil Aviation Authority carried out tests on two aircraft parked at

Gatwick, which reinforces the ban on the use of mobile phones while the engine is

running [64]. The tests revealed that interference levels varied with relatively small

changes in the phone’s location, and that the number of passengers on the flight could

affect the level, since they absorbed some of the signal. Further testing has been done

since, publicly reported in [198], which showed that at the GSM mobile frequencies it

was possible to create the following interference effects:

• compass froze or overshot actual magnetic bearing;

• instability of indicators;

• digital VOR (VHF Omnidirectional Ranging, an aeronautical navigation aid

using the VHF spectrum) navigation bearing display errors up to 5 degrees;

• VOR navigation To/From indicator reversal;

• VOR and ILS (Instrument Landing System, an aeronautical navigation aid

using the VHF spectrum) course deviation indicator errors with and without

a failure flag;

• reduced sensitivity of the ILS Localiser receiver;

• background noise on audio outputs.

Nevertheless, there is considerable public pressure to allow use of cellphones on board,

and the fact that more often than not interference doesn’t actually create problems has

led to the perception that there isn’t a problem. To deal with both of these issues, some

airlines are trialling a system which actually allows cellphones to be used via a pico-

cell base station on the aircraft, communicating via satellite with the ground networks.

The EMC implication of this is that because the base station is very local, the phones

are able to transmit at their minimum power, thus (hopefully) eliminating EMC

interactions. Even so, there will almost certainly be restrictions on use, only above

10,000 feet and not during takeoff and landing.

1.1.2 Interference to medical devices

Another critical area with potentially life-threatening consequences is the EMC of

electronic medical devices. A 1995 review article [122] described three incidents in

detail and listed more than 100 EMI problems that were reported to the US Food &

Drug Administration between 1979 and 1993. It states bluntly that:

EMI-related performance degradation in electronic medical devices has resulted in deaths,

serious injuries, and the administration of inappropriate and possibly life-threatening treatment.

† Especially if they regard their need for personal communication as more important than a mere

request from the crew. [64] reports that an aircraft carrying a German foreign minister had to make

an emergency landing “after key cockpit equipment cut out”. It was claimed that mobile phone

transmissions could be the only explanation and it was said that, “despite repeated requests from

the crew, there were still a number of journalists and foreign office personnel using their phones”.

4 EMC for Product Designers

The detailed case studies were as follows:

• apnea monitors: the essential function of an apnea monitor is to sound an

alarm when breathing stops; the devices are used in hospitals and frequently

prescribed for home use in the case of infants who either have exhibited or

are at risk of experiencing prolonged apnea. After numerous reports of

unexplained failure on the part of apnea monitors to alarm even upon death,

their susceptibility to radiated RF was evaluated by the US Center for

Devices and Radiological Health (CDRH). Most commercial apnea

monitors were found to erroneously detect respiration when exposed to

relatively low field strengths, a situation that could result in failure to alarm

during apnea. Most monitors were found to be susceptible above 1V/m; one

particular model was susceptible to pulsed fields above 0.05V/m.

• anaesthetic gas monitor: the CDRH received several reports of erroneous

displays and latch-up of an anaesthetic gas monitor during surgery. None of

the reports mentioned EMI as a possible cause. FDA investigators found

that the manufacturer had a list of 13 complaint sites, and his own

investigations revealed that interference from certain types of

electrosurgery units disrupted the communication link between the monitor

and a central mass spectrometer, causing the monitor to fail to display the

concentration of anaesthetic gas in the operating room during surgery.

• powered wheelchairs: a QA manager at a large wheelchair manufacturer

had received reports of powered wheelchairs spontaneously driving off

kerbs or piers when police or fire vehicles, harbour patrol boats, or CB or

amateur radios were in the vicinity. Though CDRH databases showed

reports of unintended motion – in several cases involving serious injury –

none of these incidents had been attributed to EMI. When CDRH

investigated the EMI susceptibility of the motion controllers on various

makes of powered wheelchairs and scooters, they discovered

susceptibilities in the range of 5 to 15V/m. At the lower end of the range, the

electric brakes would release, which could result in rolling if the chair

happened to be stopped on an incline; as the field strength at a susceptible

frequency was increased, the wheels would actually begin turning, with the

speed being a function of field strength.

Another issue is the effect on hearing aids:

The problem of interference to hearing aids has been known for some time. Digital mobile

phones use a form of radio transmission called Time Division Multiple Access (TDMA), which

works by switching the radio frequency carrier rapidly on and off. If a hearing aid user is close

to a digital mobile telephone, this switching of the radio frequency carrier may be picked up on

the circuitry of the hearing aid. Where interference occurs, this results in a buzzing noise which

varies from very faint to maximum volume of the aid... [A specialist standards panel] has

determined that, although digital mobile telephones are being looked at as the source of likely

interference, all radio systems using TDMA or similar transmissions are likely to cause some

interference.

BSI News December 1993

These are all examples of the lack of a product’s “fitness for purpose”: that is, to operate

correctly and safely in its intended environment, which includes the electromagnetic

environment. There are clear safety implications in the reports.

Introduction 5

1.1.2.1 Hospital and emergency service radio management

Many types of hospital equipment are susceptible to RF radiation from hand-portable

mobile radio transmitters – diagnostic equipment such as ECGs, EEGs, pulse oximeters

and other physiological monitoring equipment; and therapeutic equipment such as

infusion pumps, ventilators and defibrillators. Physiological (patient-coupled)

monitoring equipment is very sensitive and hence very susceptible, although for every

device type, some models consistently perform better than average (they exhibit good

EMC design). The type of modulation employed by the mobile transmitter can be

significant. For example, an external pacemaker withstood a GSM signal (modulated at

217Hz) at 30V/m field strength, but TETRA modulation (17Hz) caused interference at

3V/m.

This is of particular concern for ambulances, which in Europe are mandated to use

the TETRA system for emergency communications, but which also carry an array of

patient-coupled instrumentation for life support purposes. This has led to the UK's

Medicines and Healthcare Products Regulatory Agency (MHRA) recommending as

follows [199]:

• the use of portable handsets and cellphones inside ambulances should be

restricted;

• special precautions are needed if a patient with an external pacemaker is

being transported;

• displaying warning notices, providing staff training, and relocating parking

bays are possible actions if risks of interference prove unacceptable when

emergency vehicles are parked immediately outside patient treatment areas;

• caution should be exercised when treating patients with medical devices at

the scene of an accident if an emergency vehicle is nearby;

• mobile data terminals should be subjected to any restrictions which are

locally applied to cellphones.

Various studies have tested medical devices and recommend that a distance of 1 to 1.5m

be maintained between typical hand-portable transmitters and medical equipment. The

MHRA tested 178 different models of medical device using a wide range of radio

handsets. Overall, in 23% of tests medical devices suffered electromagnetic

interference (EMI) from handsets. 43% of these interference incidents would have had

a direct impact on patient care, and were rated as serious. Only 4% exhibited effects

with cellphones at 1m distance, although at that distance emergency and security

handsets had much greater effects [200].

The difficulty with controlling the use of radio communications in hospitals and

other medical situations is well illustrated in the MHRA’s guidance document [201],

which itself refers to an ISO technical report on the subject [170]:

Overly-restrictive policies may act as obstacles to beneficial technology and may not address

the growing need for personal communication of patients, visitors and the workforce. At the

other extreme, unmanaged use of mobile communications can place patients at risk.

The guidance stresses the need for an effective policy for healthcare providers to

manage the use of the radio frequency spectrum in their own sites. This includes

considering areas where medical devices will not be affected and therefore no

restrictions apply, and other areas where authorized staff can use communication

devices authorized by the hospital. Incidents should be reported when a medical device

is suspected to have suffered electromagnetic interference.

剩余512页未读，继续阅读

kingdomren

粉丝: 2
资源: 5

产品设计师的EMC指南：第四版

EMC for Product Designers(Fourth Edition) [Tim Williams]

EMC for Product Designers 3rd

EMC_for_Product_Designers_3E

EMC入门的书籍推荐

Autodesk Fusion 360

keyshot solidwork blender

too few template argument for class template

html网页设计作品文字,40个以大文字排版的网页设计作品

unity Visual scripting

designers guide to spice and spectre

最新资源