www.vintage-mobility.ch
20
5.
EMI / RFI WARNINGS
Electromagnetic Interference / Radio Frequency Interference
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 (EMI) and Radio Frequency
waves (RFI). EMI/RFI can come from sources such as cellular phones, mobile
two-way radios (such as walkie-talkies), radio stations, TV stations, amateur
radio (HAM) transmitters, wireless computer links, microwave signals, paging
transmitters and medium- range mobile transceivers used by emergency
vehicles. In some cases, they can cause unintended movement or damage to
the control system.
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 is 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/RFI will be minimized:
The sources of radiated EMI/RFI 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
turned 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, CDplayers, 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.
