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Introduction to the CE Mark and EMC Compliance.

Background

If you make or supply things with electricity in them they must comply with the EMC Directive This is now law in all EC Countries. If you don't like it, emigrate, but be warned the rest of the world is gradually following suit. To comply, the product must have a CE mark. In order to qualify for a CE mark some responsible person within your organisation must sign a Declaration of Conformity which states that the product complies with the appropriate EMC standards. Generally this will mean testing the product to ensure that it really is compliant.

Introduction to the CE Mark

The CE Mark is the symbol as shown on the top of this page. The letters "CE" are the abbreviation of French phrase "Conformité Européene" which literally means "European Conformity". The term initially used was "EC Mark" and it was officially replaced by "CE Marking" in the Directive 93/68/EEC in 1993. "CE Marking" is now used in all EU official documents. "CE Mark" is also in use, but it is NOT the official term.
CE Marking on a product is a manufacturer's declaration that the product complies with the essential requirements of the relevant European health, safety and environmental protection legislation. The Product Directives contain the "essential requirements" and/or "performance levels" and "Harmonised Standards" to which the products must conform. Harmonised Standards are the technical specifications (European Standards or Harmonisation Documents) which are established by several European standards agencies (CEN, CENELEC, etc). CEN stands for European Committee for Standardisation. CENELEC stands for European Committee for Electrotechnical Standardisation.
CE Marking on a product indicates to governmental officials that the product may be legally placed on the market in their country. CE Marking on a product ensures the free movement of the product within the EFTA & European Union (EU) single market, and CE Marking on a product permits the withdrawal of the non-conforming products by customs and enforcement or vigilance authorities.

Introduction to EMC Compliance and Testing.

Selecting the correct standards for your product is the first critical hurdle. Some product families may have a number of applicable standards particularly if it’s a new product which has not been seen on the market before. However, irrespective of which standard is used for testing the EMC compliance of your product the substance of the testing will remain similar. The sections below give an overview of equipment classification and of the testing that will be carried out.

Equipment Classification

Equipment classification determines the level and severity of testing and decides which specific procedure is applied for testing the equipment under test.
Class A equipment is equipment suitable for use in all establishments other than domestic and those directly connected to a low voltage power supply network which supplies buildings for domestic purposes.
Class B equipment is equipment suitable for use in domestic establishments and in establishments directly connected to a low voltage power supply network which supplies buildings used for domestic purposes.

Emissions.

Emissions testing is done to determine the levels of Radio Frequency noise being generated by the equipment being tested. These emissions could be harmful to other legitimate communications on the airwaves. This testing takes two forms as described below:

Conducted emissions:

The RF conducted back down the mains lead or other leads entering the equipment being tested is measured. Problems occur when the equipment being tested injects or induces noise onto the cables entering (from outside) the equipment being tested. Noise measurements go down to 150KHz.

Radiated emissions:

This type of emission occurs when the equipment being tested is emitting noise into the environment via interconnecting leads, poorly earthed enclosure, unscreened cables, noisy control electronics etc. Measurement of this type of emission requires the use of a broadband antenna to measure the level of RF energy radiated from the product into ‘space’. Ideally an Open Area Test Site (OATS) or equivalent should be used. Many test houses use an anechoic chamber

Immunity.

Immunity testing is carried out to ensure the effects of electromagnetic disturbances will not damage the equipment or render it inoperable.

Conducted immunity.

Surge and Electrical Fast Transients:

Surges can be considered as the net result of a lightning discharge to the National Electricity distribution grid. This lightning impulse is then severely filtered by the low-frequency response of the grid, arriving at the consumer as a low frequency (but high energy) surge.
Fast Transients can be loosely considered as 'equivalent' to the effect of switch or relay bounce.

Voltage interruptions and Voltage fluctuations:

Variations to the level of mains voltage or complete loss of that voltage is covered in this testing. One test will cycle the mains power on and off over a period. Malfunction of the equipment is assessed against a pass fail criteria.

Radiated immunity.

Radiated immunity testing requires that the equipment under test(EUT) operates satisfactorily when subject to a strong electromagnetic field. This requires a frequency scan at a certain fixed level of field strength (specified by the standard). The 'scan' will comprise a series of 'steps' in frequency. Each step is specified as a percentage of current frequency value. This percentage is variable from 0.5% to 5%.
At each step, the frequency is held, the level adjusted to the required field strength (V/m) as measured by a field sensor, a prescribed modulation mode is initiated and then the conditions held for a 'dwell' time. The EUT should be monitored to detect faulty operation during the test. Typical values for field strength are 3 V/m for domestic and 10 V/m for industrial products. These fields are so intense that this test must be carried out in a screened room or test cell.

ESD ( Electrostatic discharge).

ESD testing simulates the effect of a user touching the EUT and discharging a high voltage onto the accessible part of the EUT. Testing requires points to be tested which are accessible to the user in normal operation. Installation and/or setup is unlikely to fulfil one or both of these conditions. Maintenance and installation are not regarded as "normal operation".

- Printable version of this document (pdf).