Introduction to EMI/EMC

Written by Lieutenant Colonel Anil Kumar Nigam

Electromagnetic Radiation (EMR) and its Effects

In recent years there has been considerable discussion and concern aboutrepparttar possible hazards of electromagnetic radiation (EMR), including both RF (Radio Frequency) energy and power frequency (50-60 Hz) electromagnetic fields.

All life on Earth has adapted to survive in an environment of weak, natural low-frequency electromagnetic fields (in addition torepparttar 138904 Earth's static geomagnetic field). Natural low-frequency EM fields come from two main sources:repparttar 138905 sun and thunderstorm activity. But inrepparttar 138906 last 100 years, man-made fields at much higher intensities and with a very different spectral distribution have altered this natural EM background in ways that are not yet fully understood. It has been known sincerepparttar 138907 early days of radio that RF energy can cause interference in most ofrepparttar 138908 wireless operated systems and in devices which process extremely low power signals associated with control systems and in medical equipments. Very high density of Electromagnetic Fields have been known to have resulted in injuries by heating body tissue. These heat-related health hazards are called thermal effects. In addition, there is evidence that magnetic fields may produce biological effects at energy levels too low to cause body heating. The proposition that these thermal effects may produce harmful health consequences has produced a great deal of research. Human body nervous system is also known to work on extremely low intensities of electrical signals. Very little has been done to investigaterepparttar 138909 effect of Electromagnetic Fields onrepparttar 138910 human nervous and control system which as such leaves a lot of scope for future research.

Potential Sources of EMR The list could be endless starting with seemingly harmless AC (alternating current) operating devices to allrepparttar 138911 intentional and non- intentional transmitters. Appreciable radiation occurs asrepparttar 138912 size ofrepparttar 138913 components and connecting wires approaches one tenth ofrepparttar 138914 wavelength ofrepparttar 138915 operating frequency. The intensity ofrepparttar 138916 field so radiated also depends onrepparttar 138917 power handled byrepparttar 138918 device. To name a few tube lights, spark plugs, washing machines, music systems, power amplifiers, computers, lifts, air conditioners, cable TV, computer screen etc all fall inrepparttar 138919 category of non-intentional transmitters but can be potential source of Electromagnetic Radiations. All radio and TV broadcasting systems, telecommunication systems and equipments, RADARS, mobile phones etc are intentional transmitters of Electromagnetic Radiations and may result in typical effects on various systems in addition to causing serious interference problems and affecting human body. With ever increasing use of modern digital technology in almost allrepparttar 138920 modern processing and communication equipmentsrepparttar 138921 threat of unintentional Electromagnetic Radiation is further enhanced. As all digital signals positively have a very large bandwidth, its increasing use will result in Electromagnetic Radiations in almost allrepparttar 138922 frequency ranges there by leaving a possibility of affecting most of electronic devices and also human beings.

Some Typical Effects of EMR

Electromagnetic Interference: Interference isrepparttar 138923 energy levels introduced by electronic or communications systems that have a detrimental effect on other systems. Any electronic system is capable of receiving Electromagnetic Radiations ifrepparttar 138924 size ofrepparttar 138925 components or connecting wires approaches one tenth of frequency that may be present inrepparttar 138926 surrounding environment due to any intentional or unintentional transmitter. Depending onrepparttar 138927 intensity of this unwanted received radiation there could be instances of malfunctioning ofrepparttar 138928 device receiving this energy. There have been number of instances where such a condition had resulted in catastrophic failure ofrepparttar 138929 equipments. The most famous example isrepparttar 138930 failure ofrepparttar 138931 Electronic surveillance system installed at one ofrepparttar 138932 ships of United Kingdom Naval forces during Falkland war due to operation of its own Radar system installed onrepparttar 138933 same warship. As a result of this only one system could be operated at one time resulting inrepparttar 138934 loss ofrepparttar 138935 ship. Intentional Jamming ofrepparttar 138936 radio receivers byrepparttar 138937 security and police forces isrepparttar 138938 utilization of this effect to makerepparttar 138939 enemies receivers inoperative, however it can also happen due to unwanted and unintentional Radiation of Electromagnetic fields.

Effects on Human Body: Body tissues that are subjected to very high levels of RF energy may suffer serious heat damage. These effects depend uponrepparttar 138940 frequency ofrepparttar 138941 energy,repparttar 138942 power density ofrepparttar 138943 RF field that strikesrepparttar 138944 body, and even on factors such asrepparttar 138945 polarization ofrepparttar 138946 wave.

At frequencies nearrepparttar 138947 body's natural resonant frequency, RF energy is absorbed more efficiently, and maximum heating occurs. In adults, this frequency usually is about 35 MHz ifrepparttar 138948 person is grounded, and about 70 MHz ifrepparttar 138949 person's body is insulated fromrepparttar 138950 ground. Also, body parts may be resonant;repparttar 138951 adult head, for example is resonant around 400 MHz, while a baby's smaller head resonates near 700 MHz. Body size thus determinesrepparttar 138952 frequency at which most RF energy is absorbed. Asrepparttar 138953 frequency is increased above resonance, less RF heating generally occurs. However, additional longitudinal resonances occur at about 1 GHz nearrepparttar 138954 body surface.

Health Care Engineering: Is electromagnetic Interference (EMI) becoming a problem inrepparttar 138955 healthcare environment? Although electrical interference in hospitals is often regarded as no more than a minor nuisance, there are documented cases in which equipment failures due to Electromagnetic Interference (EMI) have lead to injury or death. Some examples fare as follows: - • In 1992, a patient attached to a monitor-defibrillator in an ambulance died because of interference fromrepparttar 138956 ambulance radio preventedrepparttar 138957 machine from working (1). • In 1987, patient monitoring systems failed to sound alarms because of interference; two patients died as a result (2).

• In 1993, a patient fitted with a pacemaker went into ventricular fibrillation shortly after being scanned with a metal detector outside a courtroom (2).

As in many other fields,repparttar 138958 amount and complexity of electronics in hospitals and other medical environments is increasing year by year. Despite this,repparttar 138959 number of reported incidents of EMC (Electromagnetic Compatibility) problems fortunately does not appear to be growing. This is probably because most manufacturers and designers of medical electronic products have developed a good awareness of EMC. Pacemakers are typical examples, where their design with respect to compactness and immunity to radio frequency interference has greatly improved overrepparttar 138960 years. Nowadays, pacemakers are very reliable, but can still fail under extreme conditions. Pacemakers have failed in patients undergoing electro surgery (2) and in other cases where patients kept mobile phones in their chest pockets, a few centimeters fromrepparttar 138961 pacemaker leads (3). The powered Wheelchair is another typical example: there are many stories of radio frequency interference. (RFI) from mobile phones or police ‘walkie-talkies’ causingrepparttar 138962 wheelchair to drive itself and its occupant into traffic. These stories are based on real occurrences; reports of incidents inrepparttar 138963 USA inrepparttar 138964 early 1990s promptedrepparttar 138965 Food and Drug Administration (FDA) to investigaterepparttar 138966 problem and recommend thatrepparttar 138967 manufacturer changerepparttar 138968 design to give an immunity of at least 20V/m to RFI.


Written by Kay L. Schlagel


I like to be touched when I walk hand in hand with my best friend. I like to be touched when my mom kisses me good night and tucks me into bed. I like to be touched when my brothers, sisters, and I wrestle onrepparttar rug. I like to be touched when my dad comes home and gives me a big bear hug. I like it when my grandma let me sit on her lap when she taught me how to sew. I like to be touched and cuddled but not, by someone I don’t know. I do not like to be touched, by anyone on my private places. I can tell them no and quickly run away. If anyone tries to touch me and it makes me feel strange or sad, I know that it’s important to tell an adult right away.

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