6
ELECTROMAGNETIC INTERFERENCE (EMI)
Therapiddevelopmentofelectronics,especiallyintheareaofcommunications,hassaturatedour
environmentwithelectromagnetic(EM)radiowavesthatareemittedbytelevision,radioand
communicationsignals.TheseEMwaveareinvisibleandtheirstrengthincreasesasoneapproachthe
source.AllelectricalconductorsactasantennastotheEMsignalsand,tovaryingdegrees,allpower
wheelchairsandscootersaresusceptibletoelectromagneticinterference(EMI).Theinterference
couldresultinabnormal,unintentionalmovementand/orerraticcontrolofthevehicle.TheUnited
StatesFoodanddrugAdministration(FDA)suggeststhatthefollowingstatementbeincorporatedto
theuser’smanualforallpowerscootersliketheS12, S12T, S12S, S12X.Powerscootersmayas
susceptibletoelectromagneticinterference(EMI),whichisinterferingelectromagnetic
energyemitte
d
fromsourcessuchasradiostations,TVstations,amateurradio(HAN)transmitter,two‐wayradios,
cellularphonesandalarmsystemsofshops.Theinterference(fromradiowavesources)cancausethe
powerscootertoreleaseitsbrakes,movebyitselformoveinunintendeddirections.Itcanalso
permanentlydamagethepoweredscooter’scontrolsystem.TheintensityoftheEMenergycanbe
measuredinvoltspermeter(V/m).EachpoweredscootercanresistEMIuptoacertainintensity.This
iscalled“immunitylevel”.Thehighertheimmunitylevelthegreatertheprotection.Atthistime,
currenttechnologyiscapableofprovidingatleast20V/mofimmunitylevel,whichwouldprovide
usefulprotectionagainstcommonsourcesofradiatedEMI.
Following the warnings listed below should reduce the chance of unintended brake release or powered
scooter movement that could result in serious injury:
1. Donotturnonhand‐heldpersonalcommunicationdevicessuchascitizensband(CB)radiosandcellular
phoneswhilethepoweredscooteristurnedon.
2. BeawareofnearbytransmitterssuchasradioorTVstationsandtrytoavoidcomingclosetothem.
3. Ifunintendedmovementorbrakereleaseoccurs,turnthepoweredscooteroffassoonasitissafe.
4. Beawarethataddingaccessoriesorcomponents,ormodifyingthepoweredscooter,maymakeitmore
susceptible to interference from radio wave sources (Note: It is difficult to evaluate the effect on the
overallimmunityofthepoweredscooter).
5. Reportallincidentsofunintendedmovementorbrakereleasetothepoweredscootermanufacturer,and
notewhetherthereisaradiowavesourcenearby.
TURNOFFYOURPOWEREDSCOOTERASSOONASPOSSIBLEWHENEXPERIENCINGTHEFOLLOWING:
Unintentionalscootermovements
Unintendedoruncontrollabledirection.
Unexpectedbrakerelease
TheFDAhaswrittentothemanufacturersofpowerscootersaskingthemtotestnewproductstobesuretheyprovidea
reasonabledegreeofimmunityagainstEMI.TheFDArequiresthatapoweredwheelchairshouldhaveanimmunitylevel
atleast20V/m,whichprovidesareasonabledegreeofprotectionagainstmorecommonsourcesofEMI.Thehigherthe
immunitylevelthegreatertheprotection.Yourpoweredscooterhasanimmunitylevelof20V/mwhichshouldprotect
againstcommonsourcesofEMI.Warning:Thescooteritselfcandisturbtheperformanceoftheelectromagneticfieldssuch
asemittedbyalarmsystemsofshops.