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The use of many items of electronics equipment in close proximity in hospital environment means that same sort of EMC problems are encountered as with other types of electronic products. However there are some special features of hospital EM environment:
• Failure of medical devices can lead to injury or death. • Some equipment found in hospitals is intentionally designed to emit electromagnetic energy, often for therapy. Other equipment, which may be located nearby, is designed to detect very small physiological signals. This combination has potential to create EMC Problems. • Also in hospitals, there is question of whether to ban or restrict use of mobile phones. They improve communications but can interfere with critical equipment. • Many medical devices are connected directly to patients. For mains-powered devices, designer must prevent electric shock as well as ensure EMC. Electronic equipment is constantly evolving, so there is always possibility of new problems arising, e.g. interference from new types of mobile communications devices.
Remedial Measures: Ensuring EMC of devices/ components: Electromagnetic compatibility describes a state in which electromagnetic environments produced by natural phenomena and by other electrical and electronic devices do not cause interference in electronic equipment and systems of interest. In order to reach this state, it is necessary to reduce emissions from sources that are controllable, or to increase immunity of equipment that may be affected, or to do both. To try to eliminate all possibility of interference by decreasing emissions and increasing immunity further could incur a high cost to industry and could prevent new technologies from emerging. For example, a restriction lowering transmitting power of cellular telephones so that consumers could place their cell phones on top of any electronic equipment might compromise performance and economic viability of such communication systems. On other hand, a requirement that all commercial electronic equipment perform without malfunction at ambient levels of 50 V/m would place a financial burden on manufacturers of a large range of equipment. The following are some of techniques used to counter effects of EMI:
Source Elimination: An effective technique to eradicate interference is through identification and elimination of source. In theory, this represents arguably most effective of any measures, but is not practical in most situations, whereas this would require source to be periodically or permanently disabled from operation. Grounding a grounding point represents a common reference point for a device or multiple devices that functions to ensure safety or equipment and operator, and its effects provide some immunity to noise and interference. Certain transmission and other Electronic equipment require adequate grounding to ensure proper operation. The Conductor used to ground equipment should be shortest necessary length to avoid a ground loop condition. This could result in energy transfer through conduction to connected devices.
Filters The use of filters allows selected frequencies to pass through to connected device, while rejecting or attenuating any frequencies that are outside filter specifications. Examples of filters include low-pass, band-pass, and high-pass.
Shielding. An effective manner used to minimize, and in some instances eliminate, EMI is to effectively shield components from interaction with electromagnetic energy. This technique is often expensive and causes major design engineering challenges, especially to fully shield a device, which requires that conductive material completely enclose equipment or circuitry. Any separation in shielding material reduces effectiveness Of shielding technique.
With ever increasing use of spectrum due to modern communication equipments and also use of latest digital processing techniques for most of devices there is a need for laying down guidelines for Emission standards. The extent of spurious radiation by any device should be limited to extent possible without increasing cost of product. Various governmental and nongovernmental agencies must come forward at national and international level to coordinate and standardize permissible radiation limits
(1)Banana Skins’, UK EMC Journal, vol. 15, p. 8, February 1998.
(2)Healthcare Engineering: Latest Developments and Applications; I Mech E, London, 25-26 Nov 2003 and Jeffrey L Silberberg, ‘Performance degradation of electronic medical devices due to Electromagnetic Interference Compliance Engineering vol. 10 p. 25 1993.
(3)Medical Devices Agency, Electromagnetic Compatibility of Medical Devices with Mobile Communications, MDA DB 9702, 1997.
Author has 28 years of experience in the field of Telecommunications. He is M.Sc(Physics) and has M. Tech from Indian Institute of Technology Kanpur. He has worked in different capacities including Signal corps ndian Army, Regional Manager of one of leading Telecom company. Currently he is Associate Professor with one of leading Engineering colleges in North India.