Safe power for medical devices used at home

February 13, 2015 //By Herbert Blum
Safe power for medical devices used at home
An aging population and the rising cost of healthcare around the world are a matter of concern to the general public these days. This is especially true in the USA, where keeping costs under control becomes more and more challenging.

In order to reduce the cost of overhead, while offering increased levels of care by way of technology, we are seeing a trend towards medical care at home. Along with this trend is increasing demand for smaller, more portable and efficient medical equipment.

While the shorter stay in overcrowded hospitals is saving costs in the health industry, manufacturers of medical devices are being presented with new challenges to minimize the safety risks associated with the use of medical devices. Medical devices used at home are being operated by laypersons with no medical training, instead of trained personnel in a controlled hospital environment. Regulatory requirements have been established to provide safety measures specifically for these users.

 As an important addition to the basic standard IEC 60601-1 for medical devices, IEC 60601-1-11 describes requirements about medical equipment used in the home. The developers of such devices or components have to observe additional requirements as it relates to safety in addition to specifications about marking (simple operation) and documentation (for example, understandable operating instructions). The utmost care has to be exercised when it comes to powering the device. The safety requirements according to IEC 60601-1-11 can be summarized as follows:

- Altered ambient conditions (domestic environment)

- Protection Class II

- Minimum IP 21 degree of water and dust protection

- Stricter shock and vibration tests

A key criteria is most certainly the responsibility to provide Protection Class II safety, as well as equipment immunity to electromagnetic interference.

Domestic power supply systems, unlike installations in hospitals, are not always reliable or may be insufficiently grounded. A medical device used at home has to compensate for this potential. It is therefore imperative that it be designed with Protection Class II safety.

Protection Class is defined in safety standards that offer protection against dangerous contact voltages. Devices in Protection Class II have double insulation between the mains circuit and the output voltage or metal enclosure. Even if they do have electrically conductive surfaces, they are protected against any contact with other live parts through the double insulation.



Icon for Protection Class II


The icon for Protection Class II symbolizes two insulation layers and is affixed to all Protection Class II devices.

The protective insulation has to be reinforced according to the general standard IEC 61140 for protection against electric shocks or be double that of Protection Class I. A second insulation for the power feed is a common solution. Doubling the clearance and creepage distances for all live contacts also has the same effect as a double insulation. 

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