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    Chapter15 standards Chapter15 standards Document Transcript

    • The University of New South Wales School of Electrical Engineering and Telecommunications ELEC3017 ELECTRICAL ENGINEERING DESIGN CHAPTER 15: STANDARDS AND THEIR IMPORTANCE IN DESIGN Lecture Notes Prepared by Mr R Lions1, Dr H.S. Blanks2 and Assoc. Prof. W.H. Holmes 1 Group Manager, Information and Communications, Standards Australia 2 Consultant SUMMARYStandards are at the same time a help to the designer and a constraint on his or her work.It is essential that the designer be fully aware of all the standards which are relevant tothe product being designed. This may vary with the places in which the product is to besold or used.This chapter looks at the types and purposes of standards, at the organizations whichwrite and issue standards and at the relations between national and internationalstandardization. It briefly discusses some particular standardization organizations andalso gives guidance on how to search for the existence of, and obtain copies of, relevantstandards.ELEC3017 Electrical Engineering Design 1 Standards
    • 1. PURPOSES OF STANDARDSStandards generally have one or more of the following purposes: 1. To cover requirements for the prevention of accidents or to minimize their effects (e.g. cycle helmets). 2. To establish agreed unit systems, common terminology and common formats of data presentation. 3. To define methods to control and measure the quality of design, products and services. 4. To facilitate interchangeability and interconnectivity of products (e.g. bolts and nuts, plugs and sockets, input and output impedances of cascaded stages). 5. To minimize unwanted side effects and by-products, e.g. Electro-Magnetic Interference (EMI), and to ensure that resources are used optimally (e.g. frequency band allocations in communications). 6. To specify the composition or construction of materials or types of products, and to specify methods by which compliance can be demonstrated. 7. To preserve individual and public health, e.g. in the workplace, or in connection with food, medication, building materials, radiation from equipment, etc. 8. To minimize needless diversity, e.g. through the establishment of preferred component values, standardized dimensions and configurations. This facilitates the interchangeability of products having essentially the same function. 9. To establish methods of measurement, calibration, testing and inspection which lead to reproducibility and are acceptable both nationally and internationally. 10. To provide guidance on the performance of specific tasks, including sound working practices and the management of quality and reliability programs. 11. To allocate resources optimally and to avoid interference in the use of resources, e.g. frequency band allocation in communication systems.2. TYPES OF STANDARDSStandards can be divided into two broad categories: 1. Mandatory Standards These are standards that are made mandatory either by being called up in legislation or by being called up in a specific contract between supplier and customer.ELEC3017 Electrical Engineering Design 2 Standards
    • Examples are standards dealing with safety and health or preserving important aspects of the public good, such as protection of the environment or compatibility of communications systems and channels. Even where a standard is not mandatory by legislation, adherence can be made mandatory if it is called up in the customer’s contract. Compliance with the mandatory standards is not only sensible, but non-adherence may result in higher penalties in the event of subsequent litigation arising from inadequate performance or reliability of the product, or from an accident caused by a defect or failure. When incorporated in legislation, the method of enforcement is generally that the product, or any item or system in which it is incorporated or installed, is not permitted to be used, sold, connected or licensed if it does not meet the standard. Examples are materials which do not conform to safety or health standards or which do not meet radio emission or interference standards. Legislative requirements can usually be satisfied if the supplier can produce test results demonstrating that the product meets the test criteria laid down in the standard. Testing, which was traditionally done in government test laboratories, is moving to the private sector because of the increasing trend of governments to privatize services they formerly provided. Thus it may well be done in the manufacturer’s own accredited laboratory or by an independent laboratory. Such test results are also able to be provided where the standard is only mandatory in the supplier/buyer contract. Note that standards compliance may not be enough to avoid legal liability – the manufacturer may still be held to be liable for death, injury or financial losses caused by a faulty or defective product. However, standards compliance could still be a legal defence even in such cases. 2. Guidance Standards These standards provide guidance and information. Examples include: • Glossaries of terms • Standards giving information about material properties • Guides for component selection, de-rating and environmental stress protection • Guides on how to conduct a reliability assurance program • Recommended methods of product performance measurement • And guides on what constitutes good workmanship Many guidance standards describe industry and market consensus or expectations, such as standards giving preferred component parameter values or industry-agreed “standard” dimensions and configurations, etc. The guidance standards, now tending to be called guides, codes of practice or handbooks, are meant to encourage quality, promote good practices and facilitate uniformity and interchangeability. They assist designers by providingELEC3017 Electrical Engineering Design 3 Standards
    • valuable ancillary information about such matters as good design practice, good workmanship and the backgrounds of the standards. They may be written by a company or organization for its own internal use or for use by its suppliers, or by a Trade Association to improve the performance and marketing effectiveness of its members, or by a government, semi- government or other national body (such as a Standards Association), to promote the social or economic welfare of the community.Standards are often written in several parts, with the first part containing minimummandatory requirements and suitable for calling up in legislation or contracts. A secondpart may then contain the recommendations and good practice guidance which helpsconsiderably with the application of the mandatory rules of the first part (the “deemedto comply” solutions). Another part might contain specifications for performance abovethe bare minimum which could be useful in special circumstances.Note that no standard is “set in concrete”, but must be recognized as representing thebest state of the art at the time of publication, and is subject to change if circumstancesrender it necessary.3. THE IMPORTANCE OF STANDARDS TO DESIGN ENGINEERSEven when a product is designed in response to a customer’s specification, it cannot beassumed that the customer knows all the statutory or other requirements, or that thesewill be stated in the initial specification.It is one of the essential initial tasks of a designer, in the Product Definition Phase, toidentify all standards relevant to the product which are mandatory by legislation in allthe places where the product will be made, sold or used. Compliance with thesestandards then becomes part of the product specification. This is particularly importantif the product being designed is for the general market (i.e. not in response to aparticular customer).It is also important to meet the industry/market consensus standards, since it will bedifficult to sell a product which does not meet the market expectations or which,because of non-standard dimensions, configuration, energy supply requirements, etc.,does not have interchangeability with competing products already on the market orcannot be connected into existing systems or transported or used in existingenvironments. (An example would be a refrigerator or washing machine too wide to fitthrough standard door openings.)Finally, the guidance standards are often very useful design aids, dealing as they do withdefined good practice, good workmanship etc. The quality standards are particularlyrelevant in this connection.ELEC3017 Electrical Engineering Design 4 Standards
    • 4. PRODUCT AND QUALITY STANDARDSPRODUCT STANDARDSProduct standards are common forms of standards. They can state their requirements intwo ways: 1. Performance Specification This defines the performance which the product is expected to provide and indicates the tests which it must pass before being considered suitable for the purpose. For example, a sample set of circuit breakers may have to show that they can switch full load several thousand times, break an overload of six times full load fifty times, and operate a few times with a short circuit on their output and a supply source capable of providing several thousand amps. Along with these and other tests, the sample group must still operate correctly at the end of the test period! However, the designer is free to make the circuit breaker in any way and using any overload sensing system which it is felt can be manufactured economically. A standard may specify several levels of performance which are necessary for various categories of performance. Users should be sure that they indicate which specific level is required whenever they call up the use of the standard. 2. Prescriptive Specification This defines such matters as the materials and dimensions etc. which must be used in the product. Thus, a specification which calls for a galvanized weatherproof enclosure prevents the use of newer products such as stainless steel or engineering plastics which might provide superior service at a lower cost. In some cases, there may be a need to specify dimensions etc. to ensure that the product is interchangeable or compatible with other devices.In practice, most standards contain elements of both prescriptive and performancerequirements. However, most modern standards, wherever possible, are written asperformance specifications, whereas in the past they tended to be written in aprescriptive way.Performance specifications have several advantages, the most important of which is thatproduct innovation is not stifled. If a manufacturer can meet the performancerequirements using new materials or a novel manufacturing technique, while stillmeeting the performance requirements of the standard (and presumably at a costadvantage), he then has a market edge which he can exploit.ELEC3017 Electrical Engineering Design 5 Standards
    • QUALITY STANDARDSOne area attracting a great deal of attention in recent years is the establishment ofstandards for quality systems. Quality standards exist for the design process (bothhardware and software), as well as for manufacturing processes and products. The mostimportant quality standards are the ISO9000 to ISO9004 series for design andmanufacturing, which have also been adopted as Australian standards with the numbersAS3900 to AS3904, and AS3563 for software.Quality management is really just applied common sense, but since a properlyimplemented quality system is now essential if a manufacturer wishes to stay inbusiness, most industries are very interested in them.It should be borne in mind that quality management standards address the managementof the process and as such are generic. They indicate a number of specific areas wheremanagement action must be considered. There is need thereafter to adapt them to theorganization to achieve a working quality system. Quality systems can be implementedin a number of stages and the standards provide guidance for implementation.A manufacturer or service provider can have their quality system audited by an externalauditor, who will certify that it complies with the appropriate standard. This may permitthem to use certain “standards marks” or may be an essential prerequisite to doingbusiness with an increasing number of quality-conscious customers.Third party quality assurance auditing is provided on a commercial, competitive basisby a number of organizations including Quality Assurance Services (a wholly ownedsubsidiary of Standards Australia), Lloyds of London, Det Norske Veritas of Norway,Underwriters Laboratories (UL), NATA, etc. An important facet of the IEC activities (see below) is the IECQ Scheme of Electronic Components of Assessed Quality. According to this scheme, component data sheets are written in standardized formats, and reliability data must also be provided in a standard form. Component quality is assured through the fact that component manufacturers who participate in the scheme must have their manufacturing quality system approved by a National Inspectorate, which itself must be approved by the IECQ Management Committee. Standards Australia has been approved as the Australian National Inspectorate. Unfortunately there is virtually no electronic component manufacturing industry left in Australia. Designers should however be aware of the scheme and that IECQ approved components can be purchased overseas.ELEC3017 Electrical Engineering Design 6 Standards
    • 5. NATIONAL STANDARDS ORGANIZATIONSSTANDARDS AUSTRALIA Within Australia, Standards Australia is recognized as the peak national standards writing organization. Standards Australia is an independent non-profit body, incorporated by Royal Charter, funded largely by the sale of publications, membership dues, fees for licensing of the use of the Standards “marks”, and a small contribution from the Commonwealth government. Standards are prepared covering a huge range of subjects, generally in response to specific requests or a survey of interested parties. Committees are established to provide a wide and balanced range of representation, with members drawn from users, suppliers, regulators and manufacturers. This provides a transparent consensus process. When an Australian standard is being prepared, the committee will consider several working drafts. After a reasonable draft standard has been prepared, it is sent to draft review (“Public Comment”), and any comments are then taken into account prior to preparation of the final draft. This, after a committee ballot, is published as a standard and put into the public domain. There is an increasing tendency, particularly in the technology areas, not to create specific Australian standards. Australia participates in the work of the international standards bodies and then adopts the international standard (with an Australian standards number). This is partly to ensure global compatibility and assist Australian exporters, but also because it generally represents international best practice. It is Australian government policy that if at all possible there should be no inconsistencies between Australian standards and those of the ISO and IEC, so that differences in standards should not constitute a barrier to international trade. However, the adoption of international standards as Australian standards does alter the local methods of operation, in that there often doesn’t appear to be a great deal happening in Australia, but suddenly there is a new Australian standard! Further, if new work is started in Australia, the first committee task is to see what is available from international sources or other countries. Where no such foreign work exists, and the work starts in Australia on “a clean sheet”, it is now normal to offer the work to an appropriate international committee as soon as it has reached a reasonably mature stage. However, there are some needs in Australia which are not recognized in international work. For example, seat belt webbing must pass an ultra-violet test in Australia, since solar conditions tend to be tougher here and some materials which are otherwise acceptable will degrade too quickly in the Australian sun. Standards Australia is the Australian member of two of the most important international standards bodies, The International Organization for Standardization (ISO) and The International Electrotechnical Commission (IEC). These are discussed further below.ELEC3017 Electrical Engineering Design 7 Standards
    • Standards Australia has an active cooperation agreement with New Zealand, whereby the standards development capabilities of the two countries are combined to produce joint Australia/New Zealand standards wherever feasible. Standards Australia also provides a comprehensive information service which is available to assist in finding out about standards, both nationally and in other countries. The use of this facility is discussed later.AUSTRALIAN COMMUNICATIONS AUTHORITY (ACA) The Australian Communications Authority (ACA), was formed on 1 July 1997 as a merger between AUSTEL, the Australian Telecommunications Authority, which was the telecommunications industry regulator, and SMA, the Spectrum Management Agency, which was responsible for radiofrequency spectrum management and radiocommunications licensing.OTHER AUSTRALIAN ORGANIZATIONS The Department of Defence, the Electricity Supply Association and the Commonwealth Department of Transport are other organizations involved in standards activities in Australia.STANDARDS ORGANIZATIONS IN THE USA The main national standards body in the USA is the American National Standards Institute (ANSI), which does not develop its own standards but acts as a clearing house for other standards. It coordinates the efforts of groups which have grown out of the learned societies, such as the IEEE, or trade associations such as the EIA (The Electronic Industries Association), and will endorse as American national standards those documents which have been developed by a proper consensus process. In addition to ANSI standards, many standards from organizations such as the IEEE (see below) have become regarded as international standards in their own right.Other important standards organizations in the USA include: • Underwriters Laboratories (UL). This is probably the most widely known civilian standards writing and testing organization in the USA. Its standards apply to materials and devices and are intended to prevent loss of life and property through fire, accidents etc. • Federal Communications Commission (FCC). The FCC is active in the fields of frequency allocation, radio frequency interference, electromagnetic compatibility and communications systems. For example, it licenses radio stations in the US.ELEC3017 Electrical Engineering Design 8 Standards
    • The FCC’s approval is also required for radio and telecommunication equipment and equipment with the potential for producing interference with communication systems. This includes most electronic products. • US Department of Defense. Of great importance for equipment going into US government service are the standards and handbooks issued by the US DoD in the form of the so-called MIL standards, bearing identification numbers MILSTD... or MILHDBK... These standards and guidance handbooks are also widely used in the USA and elsewhere for non-government procurement. • Electronic Industries Association (EIA). This association produces a very extensive range of standards and guidance publications relevant to electronics, covering general, consumer electronics, telecommunications, passive components, solid state products, electronic displays and tubes, government electronics and industrial automation. Included are the EIA’s Joint Electron Device Engineering Council (JEDEC) solid state component standards and publications. • Institute of Electrical and Electronics Engineers (IEEE). The IEEE issues standards in several fields, including electronics, software engineering and power systems. • American Society for Testing and Materials (ASTM). Produces standards on the characteristics and performance of materials. • National Fire Protection Association (NFPA). One of its standards is the National Electrical Code (NEC), which is accepted as the standard for installation of electrical equipment in most areas of the USA.NATIONAL STANDARDS ORGANIZATIONS IN OTHER COUNTRIES There are similar bodies to Standards Australia in many other countries, including the British Standards Institute (BSI) in the UK, DIN in Germany and JIS in Japan. Other countries have standards bodies with differing methods of operation and differing ownership, ranging from fully government to independent.6. INTERNATIONAL STANDARDS ORGANIZATIONSThe need for international standards was discovered very early, in 1865, when theInternational Telegraph Union (ITU) was formed to provide for the interconnection ofthe various national telegraph networks. In time there have come to be three majororganizations, each of which is now run under the auspices of the United Nations and isheadquartered in Geneva:THE INTERNATIONAL TELECOMMUNICATIONS UNION (ITU) With a slight change of name to reflect changes in technology, but retaining the acronym “ITU”, the ITU is now the pre-eminent standards setting organization forELEC3017 Electrical Engineering Design 9 Standards
    • telecommunications. The fact that you can pick up a phone somewhere and dial any of the hundreds of millions of other phones around the world is a testament to their ability to create viable standards. Before 1993, ITU had two divisions: • CCIR, the International Radio Consultative Committee, which looked after radio and mobile services. • CCITT, the International Telephone and Telegraph Consultative Committee, which looked after fixed services such as telephony and data. Following a major reorganization at the beginning of 1993, two new divisions were created to replace these: • ITU-T, the telecommunications standardization sector, which looks after all the systems aspects of communications systems, whether or not they involve radio techniques. • ITU-R, which looks after radio transmission, propagation, frequency allocation and interference aspects of global radio services.THE INTERNATIONAL ELECTROTECHNICAL COMMISSION (IEC) This organization was formed to coordinate the safety and use of electricity. During its life, its role has expanded and the IEC now produces standards not only for electrical products but also for electronic components (including PC boards), and also publishes CISPR standards for electromagnetic compatibility and interference etc. They also publish the CIE lighting standards. Much of their work involves definitions, methods of test, and standard sizes and profiles for items such as motors which need to be interchangeable.THE INTERNATIONAL ORGANIZATION FOR STANDARDIZATION (ISO) This group grew from the needs of the manufacturing community, who wanted interchangeable screw threads, standard manufacturing tolerances and many other standardized items, so they could be traded. It has grown over the years and now covers a huge range of subjects.The IEC and ISO complement each other, in the sense that there is no overlap ofstandards produced by them. Both are organized into “Technical Committees” dealingwith particular fields. These committees in turn have “Working Groups” to preparespecific standards. Most industrialized countries, including Australia, are members ofISO and IEC, and provide input to the working groups.7. THE STANDARDS PROCESSStandards are produced in many ways, generally by establishing from experience thebest options from all those that have been tried in a non-standard environment. This isgreat for slowly developing industries such as bolts and plumbing, but modern industryELEC3017 Electrical Engineering Design 10 Standards
    • is demanding faster delivery of relevant standards, particularly as the cost of being non-standard can be so expensive.Another way of setting a standard can involve market power, where a dominant supplier(or the now very popular variant, the ad hoc industry consortium) sets a standard whichothers tend to follow. These include such entities as ISA, X-Open, OMG, OSF and theATM Forum. Such standards bodies tend to get going, produce one or two standardsfairly quickly, and then fade away within a few years. Who will maintain the standardsthey set?However, the tried and best used method for creating lasting standards is the consensusprocess, i.e. with no negative votes. This requires all stakeholders to be involved in thedevelopment of the standard, and gives them a feeling of ownership of the final output.All parties get an opportunity to contribute input, and although the result will generallybe that of a clear majority rather than unanimous, most participants are happy with theoutcome.The major problem with this process is speed. Because of the number of peopleinvolved, information must be disseminated, and comments prepared, collated anddistributed several times before a document can be finalized. Where the processinvolves the participation of people from all over the globe who also have other jobs toattend to, there can be significant delays built into the system which makes the processslow.This problem is currently being studied by most national and international standardsbodies and one would hope that over the next few years a process, somewhat like theInternet RFC (Request for Comments) process, can be established for internationalstandards development. Even this system requires a group to bring order into the chaosby sitting down and sorting out the good ideas from all the comments which may bereceived. Certainly it can cut down on postal and other delays and on the quantities ofpaper used, and can provide for an extensive, interactive global discussion.8. INFORMATION ABOUT STANDARDSStandards writing organizations are generally happy to supply catalogues of theirstandards free of charge. Several maintain World Wide Web sites, and standards can bedownloaded (for a price). For example, the ITU address is http://www.itu.ch/.Design Engineers should build up a library of catalogues and standards relevant to theproducts or systems they may have to design in the future.Standards Australia provides major information centres in Sydney and Melbournewhich can assist in locating most national and international standards. It has a library ofabout 60,000 standards from national and international standards organizations aroundthe world, and also has data bases of much of the other material to assist in a search.One problem is the difficulty of obtaining and keeping up-to-date details of proprietaryand industry standards which are not endorsed as national standards. However, in manyinstances Standards Australia will know where these can be obtained.ELEC3017 Electrical Engineering Design 11 Standards
    • Standards Australia endeavours to obtain distribution right for all these documents, sothat searchers can not only inspect the standards, but if necessary also purchase copiesof them. One side benefit of adopting international standards is that the documents arethen available “off the shelf” in Australia at a price about a third of the price of theinternational version.Standards Australia also publishes useful collections of standards in particular areas, aswell as simplified guides, student versions, etc.ELEC3017 Electrical Engineering Design 12 Standards