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CHAPTER 8 – EMI Warning
All types of electrically powered vehicles, such as powered
wheelchairs and motorized scooters (in this text all types will be
referred to as “powered vehicles”) may be susceptible to
electromagnetic interference (EMI). This is from sources such as
radio and TV stations, amateur radio (HAM) transmitters, two-way
radios and cellular phones.
The interference (from radio wave sources) can cause the powered vehicle to
release its brakes, move by itself, or move in unintended direction. It can also
damage the powered vehicle’s control system. The intensity of the interfering EM
energy can be measured in volts per meter (V/m).
Each powered vehicle can resist EMI interfering electromagnetic energy (EM)
emitted up to a certain intensity. This is called its “immunity level”. The higher the
immunity level, the greater the protection. At this time, current technology is capable
of achieving an immunity level that would provide useful protection from the more
common sources of radiated EMI. This vehicle as shipped, with no further
modification, has an immunity level of 20 V/m.
There are a number of sources of relatively intense electromagnetic fields in the
everyday environment. Some of these sources are obvious and easy to avoid. Others
are not apparent and exposure is unavoidable. However, we believe that by following
the warning listed below, your risk of EMI will be minimized.
The sources of radiated EMI can be broadly classified into three types:
1. Hand-held portable transceivers (transmitters-receivers) with the antenna
mounted directly on the transmitting unit. Examples include: citizen band (CB)
radios, “walkie talkies”, security, fire and police transceivers, cellular
telephones and other personal communication devices.
NOTE:
Some cellular telephones and similar devices transmit signals while
they are ON, even when not being used.
2. Medium-range mobile transceivers such as those used in police cars, fire
trucks, ambulances and taxis. These usually have the antenna mounted on
the outside of the vehicle.
3. Long-range transmitters and transceivers such as commercial broadcast
transmitters (radio and TV broadcast antenna towers) and amateur (HAM)
radios.
NOTE:
Other types of hand held devices, such as cordless phones, laptop
computers, AM/FM radios, TV sets, CD players, cassette players and small
appliances such as electric shavers and hair dryers, as far as we know, are
not likely to cause EMI problems to your powered vehicle.
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