Introduction to EMI/EMC

Written by Lieutenant Colonel Anil Kumar Nigam

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The use of many items of electronics equipment in close proximity inrepparttar hospital environment means thatrepparttar 138904 same sort of EMC problems are encountered as with other types of electronic products. However there are some special features ofrepparttar 138905 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 hasrepparttar 138906 potential to create EMC Problems. • Also in hospitals, there isrepparttar 138907 question of whether to ban or restrictrepparttar 138908 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,repparttar 138909 designer must prevent electric shock as well as ensure EMC. Electronic equipment is constantly evolving, so there is alwaysrepparttar 138910 possibility of new problems arising, e.g. interference from new types of mobile communications devices.

Remedial Measures: Ensuring EMC ofrepparttar 138911 devices/ components: Electromagnetic compatibility describes a state in whichrepparttar 138912 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 reducerepparttar 138913 emissions from sources that are controllable, or to increaserepparttar 138914 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 loweringrepparttar 138915 transmitting power of cellular telephones so that consumers could place their cell phones on top of any electronic equipment might compromiserepparttar 138916 performance and economic viability of such communication systems. Onrepparttar 138917 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 ofrepparttar 138918 techniques used to counterrepparttar 138919 effects of EMI:

Source Elimination: An effective technique to eradicate interference is through identification and elimination ofrepparttar 138920 source. In theory, this represents arguablyrepparttar 138921 most effective of any measures, but is not practical in most situations, whereas this would requirerepparttar 138922 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 ensurerepparttar 138923 safety orrepparttar 138924 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 groundrepparttar 138925 equipment should berepparttar 138926 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 torepparttar 138927 connected device, while rejecting or attenuating any frequencies that are outsiderepparttar 138928 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 encloserepparttar 138929 equipment or circuitry. Any separation inrepparttar 138930 shielding material reducesrepparttar 138931 effectiveness Ofrepparttar 138932 shielding technique.


With ever increasing use ofrepparttar 138933 spectrum due to modern communication equipments and also use of latest digital processing techniques for most ofrepparttar 138934 devices there is a need for laying downrepparttar 138935 guidelines for Emission standards. The extent ofrepparttar 138936 spurious radiation by any device should be limited torepparttar 138937 extent possible without increasingrepparttar 138938 cost ofrepparttar 138939 product. Various governmental and nongovernmental agencies must come forward at national and international level to coordinate and standardizerepparttar 138940 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.


Written by Kay L. Schlagel

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I can say no to strangers, kids at school, and even an adult, because my body is my own. If something happens and I’m afraid to tell my family, I know I can dial 911 onrepparttar phone. My mom said if someone tries to touch me at school or threatens me with harm. Scream and yell real loud, and if I need too, pullrepparttar 138810 fire alarm. I like feeling good about myself andrepparttar 138811 feeling of being safe and well. I have learned about good and bad touch, and how important it is to tell.

Kay Schlagel is a 45 y.o living in Nebraska with 2 grown sons. She artist/author and an adult survivor of child abuse. See her sites at,, and

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