In the widely used EN 60601-1 safety standard, medical devices that use electrical power are called Medical Electrical Equipment (or ME Equipment, for short). Since devices have various levels of potential harm to patients, they are divided into groups. Because each group has different safety requirements it’s essential to understand which category a medical device belongs to.
Electrically powered devices are classified by whether they are “energized from an external electrical power source” or an internal one (like from a built-in battery). Externally powered devices are further divided into two “classes.” 60601-1 calls these three kinds of devices Class I ME Equipment, Class II ME Equipment, and Internally Powered ME Equipment. If the Internally Powered ME Equipment can be connected to a supply mains (wall socket), while connected it must meet the requirements of a 60601-1 Class I or II device.
The externally powered devices are divided into classes based on how they meet the required two Means of Protection (2xMOP).
Class I Equipment
ME Equipment in the Class I category does not rely solely on basic insulation for protection against electrical shock but also on protective earth ground for Accessible Parts or internal metal parts.
- Basic insulation is insulation that is sufficient to protect patients and device operators during normal use. This protection is achieved using air clearance and/or solid insulation.
- Protective earth ground is required so that if the basic insulation for touchable parts of the device fails the parts will not become live.
Class II Equipment
Class II ME Equipment does not rely on basic insulation and protective earth grounding for safety.* Instead, they use additional insulation to meet two Means of Protection. This addition could be in the form of reinforced insulation and/or double insulation.
- Reinforced insulation is insulation that has been increased from “basic” to a higher requirement. For example, a basic insulation may need to meet a test voltage of 3,000V, while the reinforced insulation would need to meet a test voltage of 6,000V.
- Double insulation is two layers of insulation between any Accessible Part and any live parts. The device should bear the square-within-a-square symbol to indicate it meets Class II double insulation.
*They can connect to protective earth, but “for functional reasons only,” with its use as functional earth clearly indicated. This includes three-prong power supply cords.
The Class I and Class II designations for electrical medical devices help ensure that people remain safe from electric shock with an appropriate level of protection. Check the EN 60601-1 standard carefully when designing your device.
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