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  当前位置:网站首页>>认证知识>>CE认证
  文章标题:《Guide to CE marking》
  发表日期:2004年12月7日        已经有452位读者读过此文


What does the CE mark actually mean?

The CE mark indicates that our products comply with all the applicable European directives and we can provide evidence if required. Directives applicable to Amplicon products are:
a) The EMC directive - 89/336/EEC
b) The Low Voltage directive - 73/23/EEC
Both of these have now been revised by the council directive - 93/68/EEC
CE marking is not an approval like UL or CSA which always involve independent testing, it indicates the product complies with the directives. Our quality system ensures continuing compliance as any changes we make to a product are covered by procedures which ensure that European directives are considered.

What is the EMC directive?

The EMC directive is one of many pieces of European legislation designed to produce uniform technical regulations throughout Europe. Because the standards have been selected mostly from existing international standards it is hoped to have a neutral effect with the rest of the world. The EMC directive requires products to generate no harmful emissions and be immune to electromagnetic disturbances. More technical details can be found in the answers to other questions in this guide.

What is the Low Voltage directive?

The Low Voltage Directive (73/23/EEC) directs developers to implement safety standards which apply to the products and the environment they operate in. It applies to all electrical equipment, designed to operate (normally) in the voltage range 42.4-1000Vac peak or 60-1500Vdc. Some classes of equipment may call up the LVD directive 73/23/EEC, but stipulate that no voltage limits apply, for instance the RTTE directive 1999/5/EC. Areas covered are product labelling and marking, i.e. working voltages, the design of product enclosures must ensure that users can not gain access to hazardous areas and service people must be warned of hazardous areas. The design must minimise the risk of ignition using materials that can withstand fault conditions. Cabling and insulation should be able to carry the power in the environment it is intended. Mains driven equipment sold as 'ready to use' must be fitted with a suitable mains plug with a correct fuse. PCB layout is defined in terms of track spacing (creepage distance) and component spacing. Operator areas are also defined in terms of handles, knobs, grips etc., the specification defines the temperature rise for these items, these are not allowed to exceed a certain value so as to be hazardous to the operator. External surfaces are also considered for temperature rises. It specifies maximum earth leakage current for a mains connected device, generally 3.5mA, if devices exceed this then they must carry a warning label. If Lithium batteries are fitted then warning labels must show how to dispose of them.

What is EMC?

Electro Magnetic Compatibility is the ability of an electrical/electronic device or system to function reliably in a typical electromagnetic environment (such as an industrial shop floor or a domestic home) whilst not unduly affecting that environment. It is not measurable as such but it is possible to test equipment by monitoring its emissions, or subjecting it to simulated emissions to establish Electro Magnetic Compatibility against internationally recognised standards.

What needs CE marking for EMC?

The EMC Directive is applicable to 'electrical and electronic apparatus, as well as to the equipment and installations which contain electrical and/or electronic components'. The term, 'apparatus' has been further defined by the commission as being a finished product delivering an 'intrinsic function' and 'directly usable by the end user', and can be sold as a single commercial unit. Electronic components do not need marking and the definition of 'component', which has no intrinsic function, has become a major focus of the electronics industry and in some cases is still under discussion. All PC add in-boards such as our data acquisition, serial communications and GPIB boards are not components and must be CE marked thanks to pressure from the major PC manufacturers who were worried about poorly manufactured boards affecting their CE marked computers. Built in power supplies and DC/DC converters are classified as components but a stand alone cased power supply must be CE marked. Panel instruments have been classified as components but it has become common practice to CE mark them for EMC compliance to make the panel builders job easier, remember the CE mark must now be applied to complete installations not just individual products.

Can I still buy products without a CE mark?

Legally any product that was 'in the supply chain' before Jan 1 1996 can be marketed without the CE mark for EMC compliance, so stock that was on the shelf at the beginning of 1996 may still be sold. Products that are integrated into larger systems can also be sold for service or repair purposes as it is the integrator that must take responsibility for EMC compliance of his finished system.

What about products Amplicon doesn't make?

Amplicon is responsible for all its own products and for some products it distributes for non EU suppliers. We work with all our suppliers to ensure EMC compliance of all their products but products already in the supply chain will be sold without the CE mark where appropriate. For distributed products that originate inside the EU or where the manufacturer has a representative in the EU (such as Tektronix), it is up to the first person, or their authorised representative, who puts the product into the market, to ensure compliance. Amplicon will always try to obtain and hold declarations of conformity if appropriate.

If I sell a system made up of CE marked products does it still need testing?

Strictly speaking yes if you want to be sure. You need to provide evidence that you took all the necessary steps to ensure the system you supply meets the directive.

How can I certify my product or system?

Compliance with the EMC directive can be demonstrated in one of 3 ways:
a) Self certification - which may involve having the tests done at specialist test house or in house testing.
b) Technical construction file - this requires detailing your design, specifications, drawings and all information which will convince the authorities that, if your product was tested independently it would comply. These details are submitted to a DTI competent body (normally a NAMAS accredited laboratory) for approval.
c) EC type examination by a relevant body - which is a specialised route applying to telecommunications equipment only.

What is a pre compliance test facility?

Early in 1995 Amplicon along with 3 other Sussex electronics manufacturers set up the Sussex Euro Compliance Group investing in a large screened room and the latest equipment for carrying out our own EMC tests. Although this pre compliance test facility does not compare in absolute performance with an accredited test house we know enough about the character of our screened room to confidently submit products we have tested for final checking by an accredited test house. This dramatically reduces the cost of testing and with the knowledge we have gained doing the majority of the tests ourselves we can normally quickly identify the sources of and cure for EMC problems. It also allows us to quickly check out the effect of the modifications that some of our customers ask us to make for specialised OEM applications.

Which tests do Amplicon conduct?

Amplicon's products mainly fall into the scope of 'Information technology equipment' for emissions tests and 'Generic immunity' for immunity tests.

·  Radiated Emissions
A scan from 30MHz to 1000MHz is performed at 30 metres distance.

·  Conducted Emissions
A scan from 0.15MHz to 30MHz is performed using a LISN (line impedance stabilisation network), the limits are defined using 2 different techniques, quasi peak and average.

·  Radio Frequency Electromagnetic Field (Susceptability)
This ensures the product performs to its intended functionality when subjected to a field of field strength of 3or10V/m through the frequency range of 27 MHz to 500 MHz.

·  ESD (Electro Static Discharge)
This test simulates static discharge from the human body, it takes place in open air and must not make the unit fail, an 8KV dual polarity discharge is used.

·  Fast Transients
These are induced on the mains and data cables connected to the equipment under test.
All the above tests are carried out with the product running a typical application with appropriate cables attached and varying its position to identify maximum emissions.

·  Level A or B?
There are further classifications which increase or decrease the limits of each test depending on whether the product is primarily intended for domestic or industrial applications. Amplicon's products are industrial and are always tested to level A although most products pass tougher level B limits too and if possible we certify at this level.

What certification should be supplied with CE marked products?

An EU declaration of conformity must be made once the testing is complete and a copy must be available to the authorities such as trading standards officers. The form of the declaration is laid down in Annex 1 of the EMC directive and must: a) Identify the manufacturer or its authorised representative within the European Union. b) Describe the equipment to which it relates. c) Define the standards to which conformity is declared. d) Identify the signatory who is empowered to enter in to commitments on behalf of the manufacturer or its representative. e) All CE marked Amplicon products are supplied with a generic declaration which confirms conformity. The actual declaration for each product is available to customers on request.

What is good practice?

Just buying products that are CE marked does not guarantee your system will comply. How they are installed and connected up has a significant effect to the overall compliance of your system, properly screened cables and good quality connectors combined with a level of understanding of where to concentrate your efforts is what 'good practice' is all about. Find out by reading or attending training seminars. All engineers and electronics integrators need a good understanding of the basics of EMC if they are to produce compliant systems.

Here are some hints that will help:

·  Supply lines to power supplies should always be decoupled at the point of entry or boundaries within equipment, also care should be taken on routing cables within a system or sub system to reduce loops.

·  Cabinets will only help EMC if the access points are put together to ensure good continuity to RF. Make sure surfaces are not painted and do not use long or twisted panel to panel cables.

·  Keep high speed, medium speed, low speed and DC circuits grouped together and avoid cabling, tracking, bus bars that are close to a quarter wavelength of the signal frequencies in length.

·  Minimise rise and fall times of signals and clocks as this produces high energy harmonics. Where possible use slew rate limiting devices which reduces both emissions and cross talk.

·  Minimise the output drive of circuits and try and keep the bandwidth to a minimum.

·  DC/DC converters can reduce conducted emissions and susceptability by isolating power rails and ground from the system supply. Amplicon offers a wide range of PCB mounting converters ideally suited to this purpose.

What are the penalties for non compliance?

The EMC directive requires the EU member states to take all appropriate measures to ensure compliance. In the UK it is the local authority trading standards departments and the HSE.
These agencies will test equipment thought not to comply and if they fail can prohibit sales in the
UK and Europe. They can even seize products or entire systems.
The person found guilty of knowingly supplying apparatus which contravenes the regulations or is affixing a CE mark to non compliant equipment is liable to criminal prosecution. The penalty is a fine and up to 6 months imprisonment.

I have a special requirement, can you help?

Amplicon offers technical advice and pre compliance testing to customers designing in its products. If you are considering Amplicon board level, communications or power supply products for an OEM application and would like our help contact Amplicons Technical Support team. support@amplicon.co.uk.

Is the product I already buy CE marked?

Our catalogue details all the product we sell and is right up to date when it is published. Don't forget if you need advice about products you buy from us we want to hear from you. This CE Guide should be read and used as an aid for interpretation of the CE and LVD Directives; it does not substitute for them. It simply explains and clarifies some of the most imortant aspects related to the application of the Directives.



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