Decade-Old EMC Standard Updated

Originally Published MDDI February 2002NEWS & ANALYSIS William Leventon

William Leventon

February 1, 2002

3 Min Read
Decade-Old EMC Standard Updated

Originally Published MDDI February 2002


William Leventon


The Association for the Advancement of Medical Instrumentation (AAMI) has unveiled a new electromagnetic compatibility standard for medical electrical equipment. The new standard is clearer, tougher, and more up-to-date than its predecessor, according to one of its authors.

In January, AAMI published "Medical electrical equipment—Part 1–2: General requirements for safety—collateral standard: Electromagnetic compatibility—Requirements and tests" (ANSI/ AAMI/IEC 60601-1-2:2001). The standard replaces a 1993 version published by the International Electrotechnical Commission. Unlike the first version, however, the revised edition has been adopted by AAMI and granted American National Standard status.

The new standard is based on "our estimate of the types of electromagnetic disturbances a device might encounter in a typical hospital environment," says Jeffrey Silberberg, a senior electronics engineer with CDRH. Silberberg, who co-chairs AAMI's Electromagnetic Compatibility Committee, was a member of the group that wrote the second edition.

To bring EMC procedures up to date, the new standard incorporates key advancements that have taken place in recent years. For example, the document refers to EMC standards that didn't exist at the time the first version was issued. Many of these standards describe new and improved tests for different types of electromagnetic disturbances. "These improved test methods needed to be incorporated into the standard," Silberberg says.

Overall, the document deals with electromagnetic emissions and the immunity of electrical devices used in medical practice. In the emissions area, the document includes guidelines and tests that limit energy output from medical devices. The purpose: to prevent electromagnetic disturbances that affect computers, communications devices, and other types of equipment near the devices. Unlike the first version of the standard, the new document includes emission standards for harmonic distortion and voltage fluctuations and flicker, Silberberg says.

As for immunity, the document deals with electromagnetic conditions that could cause a device to malfunction. In tests, device operation should be unaffected by such conditions, according to the standard.

To improve immunity tests, the standard lays out new pass/fail criteria for medical equipment exposed to electromagnetic disturbances. Under the first version of the standard, equipment passed the immunity test if it continued to operate according to manufacturer's specifications or failed in a manner that didn't create a safety hazard. According to Silberberg, many manufacturers interpreted the failure clause to mean that a device could fail safely under test conditions. "But a device can fail safely and still impact the health of the patient," he says. "If the device can't be used because of an electromagnetic disturbance, that can have a health impact."

For instance, Silberberg recalls the case of a cardiac ablation device tested according to the first version of the standard. Though the device's power supply failed, the manufacturer claimed the device had passed the test because the failure wasn't a safety hazard to the patient.

"That would not be called a pass under the second edition," Silberberg says. "We tried to get very specific about what is expected of a device under test conditions."

The new guidelines state that a device should maintain its essential performance and remain safe under test conditions. The standard lists a number of prohibited "degradations" that can be caused by electromagnetic disturbances. These include component failures, changes in programmable parameters, change of operating mode, and false alarms.

Users also benefit from new language requiring manufacturers to add emissions and immunity tables to their device documentation. As Silberberg puts it, the tables "give guidance to the user on how to assure that the device is compatible with the environment and the environment is compatible with the device."

Copyright ©2002 Medical Device & Diagnostic Industry

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