International EMC Compliance Simplified

Medical Device & Diagnostic Industry Magazine
MDDI Article Index

An MD&DI June 1998 Column

EMI FIELD NOTES

Selecting the right standard is crucial to attaining product certification for electromedical devices.

In the early days of electronics, electromagnetic compatibility (EMC) was not a major problem. With the advent of the computer, the introduction of electronic equipment increased exponentially. In addition, logic families began to use lower voltages and therefore became more susceptible to disturbance. This created the need to place controls on the electromagnetic environment.

EMC is a relatively new requirement for electromedical device manufacturers. Currently, the European Economic Area (EEA) requires EMC compliance as a condition of marketing electromedical devices. Certain types of devices also require EMC compliance in the United States. Many other countries are adopting the EEA's EMC requirements. Australia and New Zealand, for example, drafted laws in 1997 that require EMC compliance; these laws are similar to those for the EEA.

Addressing EMC for electronic and electromedical products was not mandatory until FDA published its guidance document, MDS-201-0004, in 1979. In 1989, the European Community published an EMC Directive that set out its EMC requirements. Although technical problems delayed implementation, it was finally adopted January 1, 1996, when it was published in the Official Journal of the European Community as document 89/336/EEC with amendments 92/31/EEC and 93/68/EEC.^1—3

INTERNATIONAL REGULATIONS

Manufacturers can achieve EMC certification in Europe by meeting the following requirements from the Medical Devices Directive (MDD).⁴ Devices must be designed to minimize risks associated with reasonably foreseeable environmental conditions such as magnetic fields, external electrical influences, electrostatic discharge, pressure, temperature, or variations in pressure and acceleration, and reciprocal interference with other devices normally used in investigations or treatment.⁵

EMC regulations have an order of precedence. The highest level is the international treaty administered by the International Telecommunications Union (ITU). This organization establishes regulations required for international operation of radio communications. ITU regulations address issues such as international safety and security frequencies; industrial, scientific, and medical (ISM) frequencies; and noninterference requirements. All EMC regulations contain some basic ITU requirements. These include:

Each country drafts its national laws based on ITU regulations. European directives may also include more stringent requirements. Although national laws must include all aspects of the directives, they may also include country-specific requirements (Figure 1).

Figure 1. EMC regulations. Legal requirements in order of precedence.

STANDARDS

Standards provide guidance for meeting the EMC requirements. In an attempt to harmonize standards, the International Electrotechnical Commission (IEC) was founded, and in 1934, it formed the International Special Committee on Radiation Interference (CISPR). CISPR now controls all standards for product emissions above 9 kHz. IEC technical committee (TC) 77, established in 1974, controls product immunity over the entire frequency spectrum, emissions at or below 9 kHz, and disturbances or emissions below 9 kHz not covered by CISPR. The IEC Advisory Council on Electromagnetic Compatibility coordinates the work of CISPR and IEC TCs. IEC works in conjunction with other standards organizations worldwide (Figure 2).

Figure 2. EMC standards organizations. The IEC works with standards organizations worldwide.

Standards are divided into four categories: product standards, product family standards, generic standards, and basic EMC standards. Product standards provide guidance for identifying characteristics necessary to operate a device properly within a specified environment. They apply to a particular type of product, system, or installation requiring special conditions or specifications. Manufacturers should refer to a product standard first when preparing a product for certification. Such product standards include radiated immunity specifications for powered wheelchairs and EMC requirements for apnea monitors.

A product family standard groups together products, systems, or installations requiring similar or special conditions, environments, or specifications. Some product family EMC standards are:

Generic standards apply to products operating in a particular environment for which no dedicated product or product family standards exist. These standards specify a set of essential minimum requirements, test procedures, and generalized performance criteria applicable to such products but do not include detailed measurement and test methods. Examples of generic EMC standards include EN 50081-1, EN 50082-1, and EN 50081-2.^6—8

Basic standards provide fundamental conditions for achieving compliance by product families, products, systems, or installations. These standards serve as reference documents for all other standards. Basic standards include IEC 100-4-2, ESD Immunity Tests, and CISPR 11^9,10 (Figure 3).

Figure 3. Standards hierarchy. Standards are divided into four categories: product standards, product family standards, generic standards, and basic standards.

EMC COMPLIANCE

Manufacturers can demonstrate EMC compliance through a variety of methods. The following is one option for electromedical device manufacturers. Manufacturers should also analyze the need for a competent or notified body for product certification.

MDD Product Classification. To obtain EMC compliance, manufacturers must identify the product classification according to annex IX of the MDD and section 4 of CISPR 11.¹¹ Products are classified as Class I, IIa, IIb, or III for the MDD and group 1 or group 2 for CISPR 11. Electromedical devices are Class A equipment (commercial) for CISPR 11. A group 2 device, such as MRI or diathermy, must intentionally use external radio frequency as part of its operation. All devices except Class I require a notified body in the certification process (Figure 4).

Figure 4. A variety of options are available for certification of electromechanical medical devices.

Quality System. Electromedical device manufacturers must also determine the quality system to be used, as required by both annex IV—VIII of the MDD and FDA's quality system regulation. For devices other than Class I, the MDD requires manufacturers to use a competent or notified body.¹²

Standards. The EMC standard for electromedical devices is EN 60601-1-2: 1995.¹³This standard specifies the following standards as applicable:

Documentation. The MDD requires manufacturers to document the following: directives with which the system is compliant; any restrictions on equipment use; safe usage requirements; intended purpose of the device (if not obvious); proper installation and operation; sterility and reuse requirements; cautions regarding performance changes; warnings related to exposure to radiation, electromagnetic fields, pressure, and so forth; materials limitations and system interactions; device disposal requirements; and clinical data. Information must reflect the requirements of IEC 60601-1.

Standards and Requirements. Manufacturers should determine standards for each directive and test the device based on each standard. Manufacturers must also determine applicable country-specific requirements, such as compliance with VDE 0871 in Germany.

EMC FUTURE FOR MEDICAL DEVICES

IEC is currently drafting IEC 60601-1-2, 2nd edition. The following are proposed changes to that standard:

CONCLUSION

Standards are still being developed for product conformity. It is the manufacturer's responsibility to determine proper specifications and requirements for meeting applicable EMC requirements. Understanding the relationship between treaties, directives, laws, standards, and certification is key to obtaining product certification with the least amount of time, effort, and frustration.

REFERENCES

1. Official J Eur Commun, No. L139, May 23, p 19, 1989.

2. Official J Eur Commun, No. L126, May 12, p 11, 1992.

3. Official J Eur Commun, No. L220, Aug. 30, 1993.

4. Official J Eur Commun, No. L169, July 12, 1993.

5. Official J Eur Commun, No. L169, annex I, section 2, clause 9.2, July 12, p 14, 1993.

6. "Generic Emissions Standard for Residential, Commercial, and Light Industry," EN 50081-1, Brussels, CEN/CENELEC, 1992.

7. "Generic Immunity Standard for Residential, Commercial, and Light Industry," EN 50082-1, Brussels, CEN/CENELEC, 1992.

8. "Generic Emissions Standard for Industry," EN 50081-2, Brussels, CEN/CENELEC, 1995.

9. "Electrostatic Discharge Immunity Test," IEC 1000-4-2, Geneva, International Electrotechnical Commission, 1995 .

10. "Limits and Methods of Measurement of Electromagnetic Disturbance Characteristics of Industrial, Scientific and Medical (ISM) Radio Frequency Equipment," CISPR 11, amendments 1 and 2, Geneva, International Special Committee on Radiation Interference, 1990, 1996.

11. Official J Eur Commun, No. L169, annex IX, July 12, pp 36­40, 1993.

12. Official J Eur Commun, No. L169, annex IV­VIII, July 12, pp 24­35, 1993.

13. "Medical Electrical Equipment, Part 1: General Requirements for Safety. Part 2: Collateral Standard: Electromagnetic Compatibility—Requirements and Tests," EN 60601-1-2, Brussels, CEN/CENELEC, 1995.

Wayne A. Hunter is a senior quality engineer with Hewlett-Packard Chemical Analysis Group (Wilmington, DE). He is a member of the U.S. national technical advisory group for CISPR/B. Bruce Fiorani is program manager, EMI/EMC for GE Medical Systems (Waukesha, WI).

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