3
EMI Warning
This vehicle has an immunity level of 30 v/m which should protect it from Electromagnetic
Interference (EMI) from radio wave sources. The rapid development of electronics, especially in the
area of communications, has saturated our environment with electromagnetic (radio) waves that are
emitted by television, radio and communication signals. These EMI waves are invisible and their
strength increases as one approaches the source. All electrical conductors act as antennas to the
EMI signals and, to varying degrees, all power wheelchairs and power scooters are susceptible to
electromagnetic interference (EMI). This interference could result in abnormal, unintentional
movement and/or erratic control of the vehicle. The United Statement is incorporated to the user's
manual for all electric power wheelchairs:
Powered wheelchairs and electric power scooters (in this text, both will be referred to as powered
wheelchairs) may be susceptible to electromagnetic interference (EMI), which is interfering
electromagnetic energy emitted from sources such as radio stations, TV stations, amateur radio
(HAM) transmitters, two-way radios and cellular phones. The interference (from radio wave sources)
can cause the powered wheelchair to release its brakes, move by itself or move in unintended
directions. It can also permanently damage the powered wheelchair's control system. The intensity
of the EMI energy can be measured in volts per meter (V/m). Each powered wheelchair can resist
EMI up to a certain intensity. This is called the "immunity level." The higher the immunity level, the
greater the protection. At this time, current technology is capable of providing at least 30 V/m of
immunity level which would provide useful protection against common sources of radiated EMI.
Following the warnings listed below should reduce the chance of unintended brake release or
powered wheelchair movement that could result in serious injury:
1)
Do not turn on hand-held personal communication devices such as citizens band (CB) radios
and cellular phones while the powered wheelchair is turned on.
2)
Be aware of nearby transmitters such as radio or TV stations and try to avoid coming close to
them.
3)
If unintended movement or brake release occurs, turn the powered wheelchair off as soon as
it is safe.
4)
Be aware that adding accessories or components, or modifying the powered wheelchair, may
make it more susceptible to interference from radio wave sources. (Note: there is no easy way
to evaluate their effect on the overall immunity of the powered wheelchair).
5)
Report all incidents of unintended movement or brake release to the powered wheelchair
manufacturer, and note whether there is a radio wave source nearby.
