Changes to EMC test approaches

EN 55032 (Electromagnetic compatibility of multimedia equipment - emission requirements) is mandatory and is effective as a harmonised emission standard in compliance with EMC Directive 2014/30/EU. The standard applies to multimedia equipment that has a rated r.m.s. AC or DC supply voltage not exceeding 600V. It incorporates three old standards into one - EN 55022: 2010 AC: 2011 (information technology equipment), EN 55013: 2013 (sound and television broadcast receivers, and associated equipment) and EN 55103-1: 2009 A1: 2012 (a product family standard for audio, video and entertainment lighting equipment for professional use).

EN 55032 is also used as an emissions ‘base standard’ by several other product family standards as the complete emissions requirement. This includes the European Telecommunications Standards Institute’s (ETSI) EN 301 489 series of standards, which specify the technical characteristics and methods of measurements for broadband data transmission system equipment, which it detailed in Annex B.

Emission tests primarily focus on the ability of the product not to emit unintentional radio frequency energy that would interfere with radio and television broadcast reception and wireless communications, such as mobile phones, Wi-Fi and Bluetooth. Emission tests also include low frequency tests for mains harmonic current, to preserve mains power quality and voltage changes, fluctuations, and flicker tests to avoid lighting flicker. Emissions may radiate from the product or be conducted over power or signal leads e.g. Ethernet cables. Immunity tests ensure that the product functions correctly in the presence of radiated fields from transmitters, conducted interference via cables and a range of transient interference events such as electrostatic discharges, power surges due to lightning or fast transients due to power switching.

New terms

As EN 55032 is an amalgamation of the previously detailed test standards, it introduced a few new terms; noticeably:

• 3.1.2 Analogue/Digital Data Port: now included within this definition are Fibre Optic Ports, which need to be treated and tested as signal and control ports if the fibre cable has either a metallic screen or metallic strain relief. Audio ports (e.g. microphone inputs and speaker outputs) longer than ten metres are also included in the scope of this standard and need to be tested for conducted emissions.
• The difference between an antenna port and a broadcast receiver tuner port is detailed; note that these ports are subject to different test limits.
• DC network power port – clarification is given.
• Multimedia Equipment (MME) – clarification is given.
• Port – Redefined.

It is important to emphasise at this point that EN 55032 does not cover intentional transmissions from radio transmitters, as these must fully comply with the European Union Radio Equipment Directive (RED) 2014/53/EU. The RED is applicable to all non-military electrical and electronic devices that intentionally emit and receive radio waves at frequencies below 3,000GHz.

EN55032 is now the only route to compliance. Not only must new products being sold in the EU comply with EN55032, older product designs that were already released onto the market before March 2017, are also required to prove compliance as there is no grandfathering allowed.

EN 55032 is an attempt to harmonise the testing on several different types of equipment, which in the past have differed greatly in their design, operation and internal technology, but which now all share very similar internal technology and functionality. The testing for a piece of IT equipment in the old EN 55022, compared to EN 55032, is therefore very similar.

However, EN 55032 now recognises that other equipment, such as set top boxes/TVs/professional audio and video equipment, have more in common with an IT device than they do a custom built separate device in their own right (as they may have done in the past when multimedia technology was not so advanced) and therefore the test approach to these devices should be the same, although the way that the different multimedia equipment is exercised during testing differs considerably from product to product.

Practicalities

For IT equipment, that was tested previously to the old EN 55022 standard, there is very little difference. Aside from the power disturbance measurement, which is no longer permitted, limit values and measurement procedures remain largely unchanged.

For other equipment, that was not previously covered by EN 55022, but which must now comply with EN55032, radiated emissions are likely to be required to be measured in a much higher GHz range, rather than up to the 1GHz requirements of some of the old standards. This will depend on the highest internally generated frequency within the product. As a lot of devices now have a PC-based architecture, their processors tend to have high frequency clock signals, which would necessitate testing radiated emissions to a higher frequency than when tested to the previous standards.

The requirements of EN55032 also demand more focus on interface ports, port type and cable options including possible length of the cables and the type of signals on each port, with previously necessary multiple measurements for multifunctional devices no longer mandated. However, EN55032 does require testing on at least one of each type of port per function. For example, if the equipment under test (EUT) has two BNC ports, one is an input and the other is an output - both ports are candidates for conducted emissions testing.

EN55032 has also added clarity regarding the applicability of the I/O port conducted emissions test, which was missing in EN55022. This limits the testing to ports that have cables that are greater than three metres long. However, audio ports (e.g. microphone inputs and speaker outputs) longer that ten metres are also included in the scope of this standard and need to be tested for conducted emissions.

Efficient testing

As manufacturers are under pressure to maintain quality, minimising the costs and time associated with EMC testing is vital. The answer to this is to be properly prepared before products are sent to the test laboratory.

A test laboratory sees many thousands of products each year – they will not be familiar with your product, so you must brief them fully. A successful testing programme is the result of you disclosing as much information to your chosen EMC test laboratory about the EUT as early as possible in the project cycle, with a special focus on the display capabilities and I/O port mix.

Details about the port type and expected cable construction can have a dramatic impact on both the test method deployed, and the time the testing takes. It is therefore vital that you give your chosen EMC testing laboratory a full understanding of the EUT, its primary and any secondary functions, display type, typical display content, display resolution capability and environmental parameters.

Before commencing testing, the laboratory undertaking the EMC tests will also require details on the ports, including whether the port lines are balanced/unbalanced, the number of lines or pairs, and whether they are screened or unscreened. This will help the laboratory to develop a realistic test plan, enabling you to more accurately anticipate time to market for products.

Test reports should contain at least the six highest emissions from the port being tested, unless they are all 10dB or more below the limit. The test report should also indicate if fewer than six emissions were observed within 10dB of the limit. Testing need only be performed at the operating ranges of the equipment under test, taking into consideration the intended market. For products intended for worldwide use, testing need only be performed twice at 230V (±10%) and 110V (±10%) -at either 50 or 60Hz.

Currently the EU is the only market harmonised to EN55032. In some cases, the test methods and setup requirements between standards are not compatible and will require otherwise seemingly redundant testing. Therefore, if manufacturers are shipping products to multiple markets outside the EU, it is likely that they will need to evaluate their product to a wider variety of standards.

Also, EN 55032 recognises that whilst a product may not be marketed globally, it may be used by the end user worldwide. For example, you might take your CE marked tablet on holiday with you to Cancun and need to charge it up via a power adapter in your hotel room. It is therefore recommended that any equipment intended for worldwide use is tested at two voltages, 110V and 230V, to cover any anomalies when supplied at an alternative voltage.

For products that have been tested to the previous standards, a simple gap analysis can be carried out and recorded in a Consultant’s Opinion Letter, which can be included in the equipment’s relevant Technical File. This letter would include where previous testing carried out meets the requirements of EN 55032, as well as identify where further testing is required.