2.4 EMI
This portion of the content will provide the user with basic information that describes
the problems with EMI, known sources of EMI, protective measures either to lessen the
possibility or exposure or to minimize the degree of exposure, and suggested action
should unexpected or erratic movement occur.
■ ELECTROMAGNETIC INTERFERENCE (EMI) FROM RADIO WAVE
SOURCES
Powered vehicle 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 mobile phones.
The interference (from radio wave sources) can cause the powered scooter to release its
brakes, move by itself, or move in unintended direction
s. It can also permanently
damage the powered scooter’s control system. The intensity of the interfering EM
energy can be measured in volts per meter (V/m). Each powered scooter 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. This powered scooter model as
shipped, with no further modification, has an immunity level of 20 V/m without any
accessories.
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 to EMI will be minimized.
The sources of radiated EMI can be broadly classified into three types:
• Hand-held portable transceivers ( transmitter -receivers with the antenna mounted
directly on the transmitting unit. Examples include: citizens band (CB) radios,
“ walkie talkie”, security, fire, and police transceivers, cellular telephones and other
personal communication devices.
