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9.1 Electromagnetic Interference (EMI) From Radio Wave Sources
Power positioning systems may be susceptible to electromagnetic interference (EMI), which is interfering
electromagnetic energy (EM) 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
power positioning system to function by itself, or activate in unintended directions. It can also permanently
damage the control system.
The intensity of the interfering EM energy can be measured in volts per meter (V/m). Each power positioning
system can resist EMI 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 at least a 20 V/m
immunity level, which would provide useful protection from the more common sources of radiated EMI.
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.
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: cellular telephones, citizen band (CB) radios,"walkie-talkies", security,
fire and police transceivers and other personal communication devices.
NOTE:
Some cellular telephones and similar devices transmit signals while they are "ON", even when
they are not being used.
2.
Medium range mobile transceivers, such as those used in police cars, fire trucks, ambulances, and taxis.
These usually have the antennae 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,
so far as we know, are not likely to cause EMI problems to your power wheelchair.
ELECTRO-MAGNETIC INTERFERENCE WARNING
WARNING!
WARNING! It is very important that you read this information regarding the possible effects
of electromagnetic interference on your Motion Concepts power positioning system.
In addition, operation of power positioning systems can create electro-magnetic interference,
the effect of which cannot be determined. Please make sure to read the associated warnings
in the user manual for your wheelchair power base.
9.0
9.0
ELECTRO-MAGNETIC INTERFERENCE (EMI) INFORMATION
ELECTRO-MAGNETIC INTERFERENCE (EMI) INFORMATION
Summary of Contents for F Series
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