How EMI/EMC Testing Makes Electronic Wheelchairs SafeApril 23, 2019
Electronic wheelchairs provide mobility assistance for 131 million people around the world every single day. Before one of these wheelchairs makes it to the market, it undergoes thorough testing to ensure it is safe for daily use. How do EMC test labs make electric wheelchairs safe?
EMC and Electronic Components
Wheelchairs are classified based on risk and range from Class I to Class III based on FDA rules and regulations.
Class I represents the lowest risk, and are subject to basic regulations.
Class II represents a medium risk and is substantially equivalent to another device that has already undergone the FDA approval process. Most electronic wheelchairs are considered class II devices.
Class III wheelchairs present the highest level of risk and may require premarket approval from the FDA. These devices undergo the most rigorous testing possible to prove safety and effectiveness. There’s only one wheelchair on the market that has earned a Class III rating.
When it comes to EMC, or electromagnetic compatibility, testing in the United States, the FCC sets all requirements for testing electric wheelchairs. Any electronic device like a wheelchair that generates and uses timing pulses at a rate higher than 9 kHz and uses digital techniques falls under the preview of the FCC. Specifically, FCC Part 18 covers industrial, scientific and medical equipment that uses radio waves but isn’t intended for radio communication.
The FDA-recognized 60601-1-2, Edition 4: 2014-2 was recently updated to cover all environments where an electronic wheelchair might be used, including in-home use and other particular situations. A pass/fair requirement is required before EMC testing of electric wheelchairs.
Electric Wheelchair Operating Environments
Electronic wheelchairs need to be capable of working in a variety of different environments, both indoors and outdoors. This means each chair needs to pass a series of tests that simulate all these locations.
In indoor environments, an electronic wheelchair must withstand any home-level electronic disturbances, such as:
- Electrostatic discharge (ESD): ± 8 kV contact discharge, ± 15 kV air discharge
- Power frequency magnetic fields: 30 A/m at 50 MHz or 60 MHz
It also needs to be able to handle conducted RF, such as those generated by amateur and professional radio stations.
- 3 V rms outside ISM and amateur radio bands between 0.15 MHz and 80 MHz
- 6 V rms in ISM and amateur radio bands between 0.15 MHz and 80 MHz
- Radiated RF: 10 V/m, 80 MHz to 2.6 GHz
Outdoors, the chair needs to be able to function with conventional sources of ambient electromagnetic energy (EME), such as :
- AM, FM and satellite radio
- Solar storms that can interfere with electronic devices
- Utility power grid transmission lines
- Broadband over power lines
- Airport radar
- Telecom transmissions
- Electrostatic discharge
- White noise
- Fluxes in the Earth’s magnetic field
If an electronic wheelchair passes these EMC tests and can function adequately in these environments, it is considered to be successful and can move on to other testing phases.
How EMC Testing Services Fit in With Other Wheelchair Testing Requirements
The 2009 RESNA Standards Volume 2, Section 2 includes EMC testing standards for electric wheelchairs, as well as scooters and accessories. To make it to the market, an electronic wheelchair has to pass EMC testing and a variety of other requirements, including:
- Dynamic stability
- Brake effectiveness
- Energy consumption
- Maximum speed, acceleration and deceleration
- Climatic tests
- Obstacle climbing
- Power and control system tests
If a new wheelchair model can pass all these tests, as well as the EMC testing, it can be made available for purchase.
Can Electric Wheelchairs Get Wet?
Are electric wheelchairs waterproof? No.
Most power wheelchairs aren’t designed for wet environments, but if you happen to encounter damp conditions — whether it’s rain and snow outdoors or the shower or sink indoors, there’s no need to panic. Start by drying it with a towel as soon as possible, then letting it sit unused in a warm, dry place for at least 12 hours. When you use it again after it gets wet, test the joystick and brakes before you leave the house. Finally, if you encounter a problem, have your wheelchair repaired professionally.