EMC Compliance Testing for Medical Devices

EMC Compliance: Important Standards for Medical Device Manufacturers 

The road to putting your medical device on the market includes many steps, including passing all necessary electromagnetic compatibility (EMC) testing. These tests play an essential role in ensuring your device doesn’t emit a significant amount of electromagnetic interference, which could be via conducted or radiated emissions. EMC compliance also verifies that your medical device will keep working properly when other electromagnetic phenomena are present. 

There are several different standards manufacturers need to keep in mind when it comes to EMC compliance. We’ve included a brief summary of each EMC test standard, as well as why it’s important for your medical device. 

EN55011 – Conducted and Radiated Emissions (CISPR 11) 

Medical electrical equipment that has a frequency that ranges between 0 Hz and 400 GHz, and that either generates or uses local radio frequency energy, will need to abide by CISPR 11. 

The standard has specific emission requirements for radio frequency (RF) disturbances that fall within a certain range. These ranges vary based on the type of device and how it is defined. 

In basic terms, this standard lays out a set of rules for industrial, scientific, and medical equipment (ISM) to ensure these devices don’t emit too much radio frequency disturbance and interfere with other electronic devices. 

Portions of the radio spectrum are reserved for ISM devices and are known as frequency bands. The CISPR 11 limits do not apply to these bands. 

Devices can fall under one of two classes, Class A and Class B.

• Class A equipment that is used in a domestic environment may cause radio interference with other equipment in its vicinity.
• Class B equipment is designed to be used in a domestic environment and will not cause radio interference with other equipment
in its vicinity

EN61000-3-2 Harmonics 

EN 61000-3-2 is another international standard that limits the amount of harmonic current that electrical equipment can inject into the power supply. Harmonics are currents that exist outside of the fundamental frequency of the power supply (50 or 60 Hz) and are caused by non-linear loads. This can include fluorescent lighting ballasts and switched-mode power supplies (SMPS). 

Limits for this standard vary based on the equipment and the country, but there are limits established for the second harmonic through the 40th harmonic currents. These limits exist to protect the power supply from overloading. Much like EN 55011, this standard also attempts to prevent interference with other equipment, particularly with sensitive devices. 

EN61000-3-3 Flicker

Flicker from a device is not only annoying and uncomfortable. It can also cause damage and be unsafe for some people. Fluctuating voltage can make lights flicker, which can be bothersome. However, it can also be dangerous for people with photosensitive epilepsy.  

While the most visible sign of flicker is lights that flash, the most important thing to think about is how the voltage is not steady to the components of the medical device or any connected items. This can cause them to wear out quicker, and/or cause “ghost” readings.

EN 61000-3-3 limits how much voltage fluctuation, and therefore flicker, can be produced by electrical equipment when connected to a public low-voltage power supply. Limits are included from the 10th harmonic through the 100th harmonic. Again, these vary based on the device and country where the equipment is marketed. 

EN61000-4-2 ESD Level 3 

Electronic equipment must be able to withstand a certain amount of electrostatic discharge (ESD). When objects of two different electrical charges interact, discharge can occur. This can be as simple as someone touching a metal object in dry winter conditions and emitting a spark. 

With the ESD level 3 requirement, equipment needs to be able to withstand an ESD discharge of ±6 kV via contact and ±8 kV via air. If not planned for, ESD discharge from built-up electricity can cause issues such as damage to screens, communication failures, and more. 

EN61000-4-3 RF Susceptibility 10V/m 

Electronic equipment also needs to be able to handle a certain level of radiated radio frequency (RF) interference, which is what EN61000-4-3 is about. With 10 V/m susceptibility, equipment needs to be able to tolerate an RF field of 10 V/m without malfunctioning. There are five levels of susceptibility (including one special, unspecified level), and 10 V/m is right in the middle at Level 3. 

EN61000-4-4 EFT Level 3 

Electrical fast transient (EFT) testing measures the effect of disturbances that come from high-voltage, sudden currents. There are four levels of EFT protection. For Level 3, equipment should be able to handle an EFT pulse of 4 kV on power supply inputs and 2 kV on control and signal ports. 

EN61000-4-5 Surge Level 3 

Similar to protecting against EFT pulses, EN 61000-4-5 is a standard that’s concerned with surge immunity. Surges can come from things like lightning strikes, motors starting, and switching transients (an abrupt circuit change). 

At Level 3, equipment needs to be able to handle a 1.5 kV surge on the power supply input and a 0.8 kV surge on signal and control ports. Generally, equipment used in commercial or industrial environments will need to meet the standards of Level 3 or higher. This is because they are more likely to experience surges. 

EN61000-4-6 RF Conducted Immunity 

Conducted immunity testing is focused on disturbances that may happen from other devices that are powered by the same power network. Electromagnetic interference (EMI) of this kind can come from nearby RF transmitters – television and radio stations, to name a couple. These conducted disturbances can overheat the devices or disrupt them by creating a voltage transient.

EN61000-4-11 Voltage Dips, Short Interruptions 

A complete power outage can keep a medical device from successfully rebooting. Voltage drop tests simulate an array of dips and dropouts of different lengths and intensities. This way, manufacturers can rest assured their devices will operate properly after brownouts, blackouts, or other disruptions. 

EN61000-4-39 Magnetic Fields

With magnetic field testing, equipment needs to go through a simulated magnetic field to confirm it will continue to operate properly. Electrodynamic microphones and cathode-ray tube (CRT) monitors are examples of devices that may need magnetic field testing.

What to know about EMC Compliance and PSUs for Your Medical Device 

As a PC-based power supply unit manufacturer, RAM Technologies is not tested on these EMC standards. However, we do meet the standards, meaning that our PSUs will not impact your compliance. If you have any questions about specific PSUs in accordance with certain standards, please contact us today. 

You can find information on our downloadable data sheets, available on each power supply page.

RAM Technologies’ power supplies are 60601-1 3.2 certified and meet 60601-1-2 EMC standards. When you’re designing your medical device and need help with a PSU,  contact us for details.