University of Twente Student Theses


Electromagnetic sources in the hospital environment : risks analysis and measures for electro-magnetic compatibility (EMC)

Jeunink, S.P.P. (2017) Electromagnetic sources in the hospital environment : risks analysis and measures for electro-magnetic compatibility (EMC).

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Abstract:The introduction of new intentional emitters in the hospital environment have raised concerns about the electromagnetic compatibility (EMC). Electromagnetic interference (EMI) created by these emitters could disrupt the function of the surrounding ME equipment. Electromagnetic compatible electrical devices operate adjacent to each other without disturbing the operation of each other. EMC is related to three factors: 1) The emission of the source. 2) The efficiency of the coupling path. 3) The immunity of the victim. There are four kinds of coupling paths: 1) Conductive 2) Inductive 3) Capacitive 4) Radiative. In this thesis the focus is only on the radiative coupling path. The severity of EMI is related to the function of the victim. In the hospital environment a multiple of intentional emitters can be present. The devices identified are the portable radio, Walkie-Talkie, cell phone, computer, tablet and long-range RFID. The devices support a multiple of wireless communication techniques on a multiple of frequencies. The emissions created by these digital wireless communication techniques can be compared to a pulse modulated signal. The field strength of the emitted signal could be calculated by using the free space propagation with an additional factor for the reflection contribution. The electromagnetic susceptibility (EMS) of medical electrical (ME) equipment is laid down in the ME EMC standard, IEC 60601-1-2. The standard has had several editions through the years. The last edition, which is not yet in force, has special immunity requirements for bands at which intentional radiators could be present. The one but last edition makes a distinction between life-supporting and non lifesupporting ME equipment and requires higher immunity for the first. For several reasons the immunity of ME equipment can be different in practice. To ensure EMC the manufacturers provide recommended separation distances for their ME equipment. These recommended separation distances do not allow emitters close by ME equipment. In practice, the use of certain emitters close by ME equipment have benefits for healthcare providers and it is difficult to ban certain emitters. Therefore these distances are mostly not followed. Separation distances can also be calculated by the information known about the emissions of the sources, the propagation characteristics and the immunity of the ME equipment. Researchers also conducted empirical studies to find separation distances for the intentional emitters. Not for all emitters the researchers came to a consensus about a safe separation distance. A more consistent and modern approach to EMC is risk based. A risk analysis method is proposed and applied to the neonatology and intensive care department of the Medisch Spectrum Twente. First the risk of EMI induced by a certain emitter to a certain victim is assessed. Of the source-victim pairs bearing a high theoretical risk after assessment, the experimental risk is determined. With the information of the risk analysis, a risk management policy is proposed to ensure EMC in these departments. The experiments showed multiple instances of EMI on the ME equipment. The experiments also pointed out that the modulation of a signal and the combination of multiple signals could have a different interference effect. Only an introductory study about the EMC of the hospital environment is done. At which only a limited number of medical instruments of a limited number of environments were tested. To have a better view on this subject, a more comprehensive and in-depth research is necessary.
Item Type:Essay (Master)
Faculty:EEMCS: Electrical Engineering, Mathematics and Computer Science
Subject:53 electrotechnology
Programme:Electrical Engineering MSc (60353)
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