Hoveround MPV5 User Manual - Page 52

Hoveround-MPV5ManualRevM 1/17/14 10:37 AM Page 52 Chapter 8 Electromagnetic Interference (EMI) Our environment is saturated with radio electromagnetic (EM) waves that originate from transmitters of television, radio and communication signals. The waves are invisible and their strength at any location is unknown but in general, the strength of a given EM wave increases as you move toward the transmitting source. All electrical conductors act as antennas to the EM signals. To varying degrees, all power wheelchairs and scooters are susceptible to electromagnetic interference. Abnormal operation in the form of unintentional movement and/or erratic control of the vehicle could result if the interference is such as to override the control system of the vehicle. The U.S. F.D.A. has suggested that the following statement be incorporated to the owner's manual for all power wheelchairs. Electromagnetic Interference (EMI) From Radio Wave Sources. Power wheelchairs and motorized scooters (in this text, both will be referred to as power wheelchairs) may be susceptible to electromagnetic interference (EMI) which is interfering 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 wheelchair to release its brakes, move by itself or move in unintended directions. It can also permanently damage the power wheelchair's control system. The intensity of the interfering EM energy can be measured in volts per meter (V/m). Each power wheelchair 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 MPV5 power 52 Chapter 8 D82008753M 10/13