Medical Electronics
EMC in medical devices – Important aspects for patient safety
By Felix Wedel, product manager, Schaffner EMV AG B
ringing a new medical device to the market is a complex task. Technical innovation or a better solution to a problem is not enough in itself. With lives on the line, flawless reliability and safety is a must. Regulatory bodies impose high standards to protect lives and ensure safe product designs. Meeting these strict requirements in the medical field requires extensive experience and expertise.
EMC (Electromagnetic compatibility) regulatory requirements are only a part of the complex requirements matrix but should not be taken lightly. Solving EMI (Electromagnetic Interference) issues and passing subsequent EMC testing can become a roadblock between product design, development, and bringing a product to market.
EMC regulatory requirements define the acceptable limits of electromagnetic interference between electrical systems. Such a system shall not propagate electromagnetic energy in conducted or radiated/spatial form above a defined level. On the other hand, electrical systems need to tolerate defined electromagnetic levels and always be able to function safely. If both conditions are met, an electric system is deemed “electromagnetically compliant.”
The limits to the described emission and tolerance levels can be found in IEC’s CISPR 11. Ideally, EMC performance is monitored continuously during a development cycle. If an EMI issue can be identified early in the design phase, solving it has a low impact on project timing and costs (“rule-of-ten”). Troubleshooting at the end of a product development cycle may even result in a re-design. That being said, an engineering team sometimes need to operate in shortened design cycles and face tough competition situations. Time to
16 December/January 2022
EMC propogation
market can be of essence. Having a good EMC filter in combination with an EMC friendly design, is a good place to start. Another important global standard for medical products is the IEC 60601-1. It describes requirements for basic safety and essential performance of medical electrical equipment (terminology IEC/EN 60601-1).
Leakage currents – Complying to the IEC/EN 60601-1 for Medical Electrical Equipment
For patient safety as well as EMI mitigation, leakage currents play an important role. These currents are an effective method for most applications to mitigate EMI, but counter-productive for high patient safety.
For medical applications leakage currents need to be limited.
In electric systems, voltage naturally exists between the live/phase connector and the voltage potential of protected earth. In normal operation small leakage currents flow from phase to protected earth. In the case of medical electrical
EMC circuit Components in Electronics
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