The revised International Medical Safety EMC Standard, IEC 60601-1-2 Edition 4, which takes effect in Europe, USA (new applications) and Canada, defines the basic and essential performance for medical equipment regarding emissions and immunity to electromagnetic disturbances.
Edition 4 responds to the increasing number of electrical devices being used directly by patients in the home healthcare environment, outside of hospitals or professional healthcare facilities. It shifts classification of the EMC requirements from relating to the usage of a medical electrical device (life supporting or non-life supporting) to the intended user and environment of a medical electrical device (home healthcare, hospital, special environment).
The home environment will often feature more mobile transmitters situated close to medical electrical devices, so immunity requirements have been revised to ensure that the devices can be operated safely in the current and future intended environments.
The revised standard requires manufacturers to take EMC into account in the risk management process and, in the risk management file, identify all risks affecting the basic safety of a medical electrical device. The practical outcome of a risk management file is a detailed EMC test plan, which the manufacturer will need to prepare prior to testing, ideally involving the EMC testing laboratory in its preparation.
The main elements in an EMC test plan are:
- Essential performances of the equipment (affecting basic safety)
- Detailed PASS / FAIL criteria for each essential performance
- The method of monitoring each essential performance while testing
- Test setups of the equipment under test (accessories, cables, operating modes etc.)
Immunity requirements have been revised to ensure that the medical electrical devices can be operated safely in the current and future intended environments. Electrical discharge immunity (IEC 61000-4-2), radiated RF field immunity (IEC 61000-4-3) and radiated magnetic field immunity (IEC 61000-4-8) requirements have been fully revised having much higher requirements now. Also, the requirements for conducted RF immunity take into account ISM and radio amateur frequencies. The radiated RF field immunity testing has been extended to cover a near field immunity testing which simulates the close proximity of external transmitters. For the devices to be installed in a vehicle a new EMC requirement of conducted transients (ISO 7632) has been introduced.
Emission requirements remain largely unchanged - for information and multimedia equipment a product standard of CISPR 32 may be used. A new test for the patient cables emissions has been introduced as an informative annex.
The risk management process
Through the risk management process the manufacturer defines final EMC testing requirements. Manufacturers should consider the level of risk together with the test levels given in the EMC standard. The conclusion may be that different test levels, different test frequencies or different types of EMC interferences from the given requirements in the EMC standard shall be considered. It becomes the manufacturer’s responsibility to define the final EMC requirements based on the risk management.
Requirements given in the EMC standard are a starting point and the manufacturer will need to evaluate the remaining risk if the requirements of the EMC standard have been used. If the remaining risk is at too high level, then the manufacturer has to take action to lower the risk. In this phase new test levels, new test frequencies, new EMC interferences will need to be considered and applied to bring risk within acceptable levels.
Mr. Tuomo Hietanen, Project Manager for SGS said: “The concept of risk management is something new to many manufacturers and to many EMC testing laboratories and, although manufacturers still have a few months to prepare for the new EMC requirements, we’d urge them not to leave it too late.
“SGS operates the biggest, fully equipped and most effective network of EMC testing facilities in the world. Our personnel are fully trained and ready to help customers through the new procedures and requirements of the revised publication and support the manufacturer in testing and confirming the compliance of all medical electrical equipment to the new EMC requirements.”
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