UL 60601-1 and CAN/CSA C22.2 No. 60601-1

With the publication of the fourth edition of IEC 60601-1-2 [1] and its European equivalent, EN 60601-1-2 [2] being listed in the Official Journal, the EMC requirements for medical electronic devices changed. Products that will remain in production after the mandatory effective date of December 31, 2018 may require redesign to comply with the requirements of the fourth edition. Changes in design will also affect the FDA approval. Even if no changes are required, testing will need to be performed to assess the product’s performance in light of the expanded scope of testing of this new edition for the EU. There is no grandfathering of equipment that was assessed using the third edition of the standard in the EU. A presumption of conformity with the essential requirements of the Medical Device Directive (MDD) may only be assumed if the new edition is employed after the transition date. For the sake of brevity, whenever I refer to the standard, I am talking about the fourth edition of IEC 60601-1-2 and EN 60601-1-2.

Test Requirements: Emissions

The emissions requirements are found in Table 2 of the standard and cover conducted and radiated emissions using the limits and methods of CISPR 11, harmonic distortion using IEC 61000-3-2 and voltage fluctuations and flicker using IEC 61000-3-3. The application of IEC 61000-3-2 and IEC 61000-3-3 depends on the use environment. Different requirements may be necessary based on other uses, such as in transportation.

Test Requirements: Immunity

Performance Requirements

As you read the standard, you eventually get to the section on immunity requirements for ME equipment and systems. The test levels to be used are described in the standard for two types of environments. Use of higher or lower values may be used depending on the outcome of the risk management process.

At first glance, you may decide that degradations of performance are not allowed during the tests and that your product will not be able to meet a performance criteria without a significant redesign. However, as stated, the intent of this section is to describe these degradations in light of the Essential Performance and Basic Safety of the product being tested. The product is allowed to exhibit degradations that do not affect Essential Performance and safety during the tests.

Basic Safety and Essential Performance

What are Basic Safety and Essential Performance? These are defined terms in the standard IEC 60601-1. Basic Safety is “freedom from unacceptable risk directly caused by physical hazards when ME equipment is used under normal condition and single fault condition.” Essential Performance is “performance necessary to achieve freedom from unacceptable risk.” According to the standard, a risk management process shall be used to identify risks from electromagnetic disturbances in addition to any other risks.” Annex F provides additional guidance for including the risks from electromagnetic disturbances in the risk management process described in ISO 14971. The risk management report produced by the process provides the description of pass fail criteria for each function of the product and how the basic safety and essential performance will be monitored during each immunity test. This information is incorporated in the EMC test plan. This test plan is required prior to starting any EMC testing. An example is provided in Annex G of the standard.

The implication here is that you should perform a risk analysis (see Annex F of the standard for more details) prior to establishing the compliance criteria to avoid the need to perform more tests against more stringent criteria. Depending on the class of device as determined from Annex I of the medical device directive, a notified body will likely need to be consulted in determining the performance criteria to apply based on the risk analysis. The establishing of the performance criteria is crucial to evaluating the observations made of product operation during immunity tests and in determining the methods used to monitor the product. The risk analysis must account for all manners of use of the product. After assessing all the risks and determining the residual risk level, you enumerate the compliance criteria. Examples of criteria can be found in Annex I of the standard.

Tests

Now that you have established the compliance criteria you will use during the immunity tests, you are ready to test. Not so fast. The standard requires a completed test plan be prepared prior to the start of formal testing. The recommended content of the test plan is given in Annex G of the standard. The standard includes the normal set of immunity tests that are to be applied and describes test levels for special environments in Annex E. The tests are the same tests that are applied for other products such as radio equipment, networking equipment and information technology equipment except that the standard incorporates some specific test application guidance notes that require special consideration. Tables 4 through 8 list the immunity tests applicable to medical devices and the basic levels for both professional healthcare facility and home healthcare environments.

The list may include additional tests and the test specification column may change based on the type of equipment to be evaluated and particular standard that would therefore apply. It is beyond the scope of this paper to present the appropriate specifications for all medical devices. However, some examples can serve to illustrate the point. EN 60601-2-24, particular to infusion pumps, modifies the test specifications: radiated immunity test level changes to 10 V/m even if the product is for professional healthcare environments; magnetic immunity test level increases to 400 A/m. EN 60601-2-10, particular to nerve stimulators, adds that patient leads are to be placed in saline solution during testing. EN 60601-2-2, particular to HF surgical equipment, modifies the compliance criteria and the emissions test configuration.

To evaluate the DFS functions of a system the regulatory standards describe waveforms to be used when evaluating DFS. These waveforms are defined in terms of the number of pulses, the pulse width and the pulse repetition frequency (or period) for the radar signal. The pulses may be modulated with an FM chirp, and may contain pulses of different widths and different periods.  Manufacturers should always bear in mind that their radar detection algorithms should be designed to detect all radar systems.

Table 1: Immunity Tests
Environmental Phenomena	Test Specification	Test Setup
Electrostatic Discharge	±8kV (Contact) ±2, 4, 8, 15kV (Air)	EN 61000-4-2
RF Fields	80 – 2700 MHz 3V/m (professional healthcare facilities) or 10V/m (home use) 80% AM, 1 kHz	EN 61000-4-3
RF Proximity fields	Various frequencies up to 28 V/m	EN 61000-4-3
Fast transients Power Signal	5/50ns, 100 kHz ±2.0 kV ±1.0 kV	EN 61000-4-4
Surges Line to PE Line to Line Outdoor SIP/SOP	1.2/50μS ±0.5, 1.0 & 2.0kV ±0.5 & 1.0 kV ± 2 kV line to ground	EN 61000-4-5
RF Voltage (Conducted Immunity)	0.15 – 80 MHz 3V (6V in some frequency ranges) 80% AM, 1 kHz	EN 61000-4-6
Magnetic Fields*	50 Hz 30A/M	EN 61000-4-8
Voltage Dips	100%, 0.5 cycles at various phase angles 100%, 1 cycle 30%, 25/30 cycles	EN 61000-4-11
Voltage Interruption	100% for 250/300 cycles	EN 61000-4-11
*Applies only if the product has magnetically sensitive components or circuity

 

The standard has higher test levels for ESD and magnetic field immunity, magnetic field immunity may not be needed, additional RF field immunity requirements with potentially higher levels and additional VDI requirements compared to the previous edition. It also makes clear the need for a test plan prior to testing. Depending on the product, the test plan may need to include other tests or test levels that will also need to be evaluated based on the intended use of the product.

Basic Immunity Test Modifiers

For some of the immunity tests, the standard specifies modifications to the methods of the basic standards listed in table 1 above.

For example:

The dwell time at each frequency step for conducted and radiated immunity must be set to allow the product to be fully evaluated at each step. Dwell times exceeding 15 seconds are not uncommon.

Electrical fast transient tests are not performed on patient cables.

During conducted emissions, electrical fast transient/burst and conducted immunity tests, patient coupled parts shall be terminated with artificial hands.

CDNs shall not be used for conducted immunity tests on patient leads.

Power input voltage and frequency are specified for each test in Table 1 of the standard. In most cases, the tests are performed at one voltage and one frequency from the ranges of voltage and frequency for which the product is rated. Voltage dips and short interruption tests shall be performed at the minimum and maximum rated voltages if the product has rated voltage range ≥ 25% of the minimum rated voltage.

Product Information

Assuming that you have performed all of the appropriate emissions and immunity tests using the compliance criteria specified in the test plan with acceptable results, the requirements of the standard are still not yet fulfilled. The standard requires information about EMC to be included in the instructions furnished to the user. These can be found in Clause 5. The tables of information there were part of the third edition of the standard are not included in the fourth edition.

The instructions shall also provide technical information such as compliance information for each test and test levels for immunity. The justification for using the levels other than described in the standard shall be provided in the instructions. Instructions necessary for maintaining BASIC SAFETY and ESSENTIAL PERFORMANCE with regard to electromagnetic disturbances shall also be provided.

Radio Functions in Medical Devices

If a radio is provided with the product either internally or as a separate unit, the radio part of the device or system may only need approval against the applicable radio standards. However, if the function of the radio affects the essential performance of the system, then the radio and medical device both must be evaluated for immunity using the medical equipment standard.

The emissions of the radio part must comply with the medical equipment standard except in the dedicated transmission band. This means that spurious emissions of the radio must meet the CISPR 11 limits, which in most cases are more restrictive than the spurious emissions limits for the radio device.

Summary

The new edition of EN 60601-1-2 presents many challenges to manufacturers. From the beginning of the design process, manufacturers are encouraged to seek assistance from test labs and certification agencies to understand the provisions of EN 60601-1-2 as they apply to their specific product.

References

[1] IEC 60601-1-2:2014, International Standard for Medical electric equipment – Part 1-2: General requirements for basic safety – Collateral standard: Electromagnetic compatibility – Requirements and tests.

[2] EN 60601-1-2:2015, European Standard for Medical electric equipment – Part 1-2: General requirements for basic safety – Collateral standard: Electromagnetic compatibility – Requirements and tests.