EMC in medical technology: The 4th edition of IEC 60601-1-2

60601-1-2 is the EMC standard for the 60601 family of standards, meaning it applies in principle to all medical electrical devices. The full name of the standard, DIN EN 60601-1-2:2016, is:

“Medical electrical equipment – Part 1-2: General requirements for basic safety and essential performance – Collateral standard: Electromagnetic disturbances – Requirements and tests”

The new edition has many interesting changes and new focuses:

• The increasing use of medical devices in the home environment is taken into account. The home environment is not a controlled environment like a hospital environment with professional users.
• In addition, the proliferation of mobile devices with radio interfaces is adequately considered for the first time. These devices require high levels of interference immunity due to their proximity and widespread use.
• Risk assessment is becoming increasingly important, which is sensible given the significant differences between various medical devices (from equipment carts to CT scanners). Risk analysis is the best way for manufacturers to assess the impact of risks on basic safety and key performance characteristics and define measures. This then leads to tests that must be documented in a test plan.

Most medical device manufacturers have already begun the transition, and new devices have been able to be tested and approved in the EU according to the new edition since 2016. However, it should not be forgotten that as of January 1, 2019, older, long-approved devices may no longer be marketed in the EU if they do not comply with the 4th edition of 60601-1-2!

Requirements in the new edition

When looking at the 3rd and 4th editions of the standard, you'll find many differences. To give you an idea of the changes, the following are listed:

• Previously, the emphasis was on the device; now the focus is on the environment. For example, the "life-supporting device" category has been eliminated; instead, there are now three categories: clinical environment, home environment, and special environments such as military applications. The focus is now on meeting basic safety and essential performance characteristics.
• The requirements for immunity and emission depend on the location of use.
• Higher test levels for ESD up to 15 kV for air discharge, although the standard recommends testing at higher levels if necessary. Connectors are also now tested differently.
• With the 4th edition, the test criteria depend on the environment in which the device is to be used.
• The field strength for magnetic fields was increased to 30 A/m, a tenfold increase.
• Electrical transient tests have been introduced for devices intended for use in vehicles.
• EMC must definitely be considered in risk management.
• An EMC test plan is required.
• New immunity requirement for ISM frequency bands up to 28 V/m.
• Interference immunity is now tested up to 2.7 GHz (previously 2.5 GHz). The requirements have otherwise changed, primarily with regard to the classification of the environment.
• It was defined how errors occurring during the immunity test should be handled.
• The references to other standards now all have a date, meaning they always refer to a specific version of another standard. This was not done consistently in the 3rd edition, leading to some inconsistencies and ambiguities. However, this also means that the current versions of the standards are no longer necessarily referenced (for example, there is already a newer edition of CISPR 11).

But don't worry, the new standard is quite useful and offers many suggestions in the appendices on how risk management can look and what the testing should be aimed for.

Risk management

In risk management, the device manufacturer must address the essential performance characteristics of the device. They must select appropriate immunity levels to ensure that the risk of failure or erroneous behavior is as low as possible. These levels could also be higher than those required by the standard. However, risk management also allows risks to be reduced in other ways, e.g., through status messages, warnings, or similar, which was not possible after the 3rd edition. It is therefore important for the device manufacturer to understand this concept and the underlying philosophy of essential performance and basic safety! Essential performance characteristics can be identified by the fact that their absence or deterioration would lead to an unacceptable risk. So, be clear about what the essential performance characteristics of your device are and how basic safety is ensured. Then you can also assess whether these features and functions can be affected by electromagnetic interference and how this can be tested.

Also, not every device necessarily has to meet the immunity requirement against 28 V/m at the ISM frequencies – but only if this does not pose a risk.

It's easiest to refer to the Part 2 standards for the essential performance characteristics. However, sometimes, as a manufacturer, you have to define requirements based on your own experience. For example, when it comes to special operating modes and settings during device testing.

Immunity

The following table shows some of the changes regarding immunity (according to Tables 4, 5 and 6 of IEC 60601-1-2):

Many immunity tests are not applicable to cables shorter than 3 m. However, please note that country-specific variations apply! For example, in the USA, cables shorter than 3 m should also be tested.

A major change with the new edition is the requirement for immunity to radiated fields in ISM frequency bands—a very useful test given the widespread use of cell phones and other radio devices. The requirements are shown in the following table (adapted from Table 9 of the 4th edition):

During these tests, the distance to the antenna may be reduced to as little as 1 m, which may be necessary to achieve the specified field strengths.

Test plan

The EMC test plan was often created even after the 3rd edition. Now, the test plan is defined as a requirement in the standard. An appendix to the 4th edition provides assistance in creating it and lists the necessary content, which must include, among other things:

• Description of the system
• Intended purpose and operating environment
• Key features
• Key features
• Pass/Fail Criteria
• Methods of monitoring
• Number of test subjects
• Test levels for immunity tests
• Simulators and other testing equipment
• ESD test points

schedule

In 2014, the 4th edition of IEC 60601-1-2 was published, followed by a German version as DIN EN in 2016. A transition period applies in the EU until December 31, 2018. This means that starting next year, only the 4th edition of IEC 60601-1-2 will be valid!

Incidentally, the same deadline also applies to the USA, after the FDA extended the transition period several times. However, there is a difference between the USA and the EU: In the EU, all medical electrical devices tested according to 60601-1 and placed on the market after December 31, 2018, must comply with the 4th edition of 60601-1-2. In the USA, grandfathering applies: Devices already approved according to the previous edition of the standard may continue to be produced and sold. Compliance with the new edition only becomes necessary if the device is modified or re-approved.

For some countries, such as China, it may be necessary to test according to an older edition if these countries still require the 2nd edition of 60601-1 for approval.

Our proposal for action

Are you pressed for time and would like to transition to the new edition without too much hassle? Then you can utilize our contacts and our methodology. We're happy to support you with the following steps:

• Create a gap analysis based on your device. The gap analysis should answer the following questions and generate the necessary documents:
  • Which tests need to be repeated or performed?
  • Creation of the EMC test plan.
  • What changes and additions are necessary to the risk management documents?
  • What follow-up tests are necessary? Will any changes to the circuitry be required to achieve higher immunity?
• Talk to your EMC test laboratory early
• Pre-tests are recommended before the actual test to save costs and make the admission test more predictable.
• Finally, the tests are performed in an external EMC laboratory. We are also happy to support you in supervising the tests.

Conclusion

In summary, compliance with the 4th edition requires the following points:

• A test plan
• A passed examination for the tests required in the standard and determined in risk management
• A test report that meets the criteria of Chapter 9 of the 4th edition.
• A risk management process as detailed in Appendix F.
• A standard-compliant type plate and instructions on the device, as well as instructions in the technical documentation.

This article compares the 3rd edition of 60601-1-2 from 2007 and the 4th edition from 2015 (IEC). The changes are sensible and necessary to meet the demands of the modern environment. However, you should be aware that passing a test according to the 3rd edition does not necessarily mean compliance with the 4th edition, just as conformity with the 4th edition does not necessarily result in conformity with the 3rd edition. The focus and tests in the two editions of the standard are too different for that to be the case.

We're happy to support you with your EMC testing by providing measuring equipment, experience, and contacts to EMC specialists and laboratories. And don't forget, all tests should be completed by the end of 2018!

Best regards
Martin Bosch