Information Technology (IT) Equipment:  EN 55022 & EN 55024

• Overview
• Determining Highest Frequency for Emissions Testing
• Sample Test Matrix
• Technical Notes Concerning I/O Cables
• Miscellaneous Technical Notes
• Scheduling

Overview

Typical equipment falling under this category include desktop computers, laptop computers, file servers, computer peripherals, digital data recording and/or data storage devices, etc.

EMC testing for the European Union includes compliance with both emissions and immunity standards.  Emissions from IT equipment are regulated by EN 55022 and immunity is regulated by EN 55024.  As of January 1, 2001, compliance with AC power line harmonics (EN 61000-3-2) and AC power line flicker (EN 61000-3-3) is also required.  These last two standards apply to most single-phase products that connect to the AC power mains and draw less than 16 Amps of current. Amendment A1 to EN 55022 introduced radiated electric field emission limits from 1-6 GHz. This is important for several reasons. First, the limits from 1-3 GHz are 4 dB more stringent than comparable FCC limits. Second, limits are specified for this frequency range only at a distance of 3 meters, using the new measurement techniques and site VSWR requirements defined by the updated version of CISPR 16.

In the United States, compliance of Information Technology (IT) equipment with federal requirements is governed by the Federal Communications Commission (FCC).  Limits are defined by the Code of Federal Regulations (CFR) Title 47, Part 15, which regulates the emissions (unintentional and intentional) from a product up to 40 GHz.

Standards for Eastern Rim countries, as well as Australia and New Zealand are based on CISPR 22. Since EN 55022 is also based largely on CISPR 22, these standards are for the most part, very similar. The main difference is that each country specifies that testing of the UUT be performed at that country’s nominal AC voltage. While some standards give labs latitude in determining a worst case voltage, allowing for a degree of optimization in the testing matrix, there is a good chance that much, if not all of the EMC testing must be performed at multiple voltages to satisfy in-country requirements.

It is also important to realize that presently, EMC testing for Japan and Taiwan entails only emissions testing, while testing for Korea includes both emissions and immunity.

While getting a VCCI certificate using EMCI’s data is a straight-forward process, getting the KCC mark for Korea and the BSMI mark for Taiwan are more involved, more time-consuming and more expensive. EMC Integrity has tested numerous products and done nearly as many submittals for Taiwan and Korea. While there are a number of forms to be completed and items to be submitted, EMCI provides project management for these processes and, as a Nemko partner lab (Nemko ELA 215), our turn-around times are among the best in the industry.

EMCI has a thorough knowledge of the standards, what is required to meet these standards and how to get international approvals. As such, we have designed our test facilities so that our data will be accepted anywhere in the world. (The only exception to this is China, which currently requires in-country testing for EMC. While a mutual recognition agreement (MRA) is in process, it most likely will not go into effect for a few more years.) It is important to realize that for radiated emissions data from 30 MHz to 1 GHz, nearly the entire world will require and accept only 10-meter data. Technically, 3-meter data is only acceptable for 1) FCC Class B, 2) intentional transmitters and 3) emissions data taken above 1 GHz. While CISPR 22 and EN 55022 do allow for radiated emissions on Class B products to be measured at a distance of 3 meters “…if the field-strength measurement at 10 m cannot be made because of high ambient noise levels…” (Ref. EN 55022: 2006 + A1: 2007, Section 10.3.1), this is the only exclusion given. Far East countries simply will not accept RE data from 30 MHz to 1 GHz at anything less than 10 meters.

Even in a strong economy, companies are worried about cost. How much more important is cost in our current economic environment? The world-wide market offers huge opportunities for American manufacturers, but companies can be intimidated by not only the process, but also the cost of getting international approvals. When doing testing for world-wide compliance, EMCI can optimize a test matrix which will save clients literally thousands of dollars in EMC testing costs.

Determining Highest Frequency for Emissions Testing [top of page]

In general, compliance testing for the EU is more stringent than for the U.S. because both emissions and immunity are required.  However, there is one notable exception for IT equipment.  The European standard, EN55022, only regulates unintentional radiated emission levels from a product up to 1 GHz, while the FCC uses the following criteria* for unintentional radiators to determine the highest frequency of measurement:

*information in table taken from CFR 47, Part 15

Other countries have also adopted EMC standards as part of their agency requirements.  While these countries typically require the same emission limits as EN 55022, there are a number of logistical details which need to be addressed for compliance.  Contact EMC Integrity for more information.

Sample Test Matrix [top of page]

A typical test matrix for an ITE product for compliance with both EU and FCC requirements is contained in the table below.

Technical Notes Concerning I/O Cables [top of page]

Approximately 80% of EMC compliance issues are related to cables.  Power and I/O cables create the “antenna structure” for a product.  These unintentional antennas can both radiate electromagnetic energy generated by electronics inside the product and receive electromagnetic energy impinged upon the product.  The former could result in non-compliance with regard to emissions and the latter could create an immunity problem.

Since cables are an integral part of a product’s function and configuration, clients should realize some significant factors about cables prior to testing for EMC compliance.

• For emissions testing, all I/O ports should be loaded with a cable; for FCC only, ANSI C63.4 specifies a minimum cable length of at least 1 meter, while CISPR 16 requires the cable length be at least 2 meter long
• Exclusions may apply for service and maintenance cables
• For immunity testing, if a cable can be greater than 3 meters in length, electrical fast transient testing via capacitive clamp applies to this cable
• Non conductive cables (e.g., fiber optic or plastic tubes) are exempt from cable testing requirements

Miscellaneous Technical Notes [top of page]

Note 1.   Whether a product is tested to Class A or Class B limits for emissions depends on where it will be used.  If a product may be used in a residential environment, it should meet the Class B limits, which are 10 dB more stringent than Class A.  If a product will only be used in commercial, office or industrial environments, the Class A limit then applies.

Note 2.   When measuring the radiated E-field emissions for both Taiwanese and EU compliance, we recommend performing a “pre-scan” at both 110 Vac and 230 Vac. The formal testing can then be performed at the worst-case voltage, satisfying both BSMI and EU requirements. However, it is important to note that this applies only to radiated emissions. It should further be noted that all testing for VCCI and KCC must be performed at the in-country voltage.

Note 3.   When performing immunity testing, keep in mind that the product will need to be monitored to ensure that its level of performance meets the requirement defined for the test being performed.  Different tests have different performance criteria, which are summarized as follows:

Level A:    The equipment shall continue to operate as intended without user intervention.

Level B:     After the test, the equipment shall continue to operate as intended without user intervention.

Level C:     Loss of function is allowed, provided that the product can be restored by the operation of controls (i.e., no permanent damage).

The performance criterion for each immunity test is listed in the following table.

Scheduling [top of page]

EMC Integrity generates a detailed quotation for all formal compliance testing that we perform.  Our quotations state the name of the product to be tested, the standards to which the product will be tested, the individual tests that will be performed and any additional testing that may be requested by the client.  Tests are listed on a line-item basis, thus clearly delineating both the scope of work and the cost of each test.  An outline of our process is given below.

Overview of EMCI’s RFQ Process.