Hi it’s me again, the guy in the Top Hat , standing in the spotlight of the First Ring under the Big Top. There see the Lions, Tigers, Bears and Elephants who roar, snarl , growl and trumpet. Their sounds travel well beyond the ring and powerfully impress the audience. The animals paw and pound the ground under the watchful eyes of their trainers . If they were to escape , they would wreak havoc on the crowds and the whole circus grounds. Even just their voices and movements already affects some of the audience. These animals are metaphorically the Sources in the EMC Circus.
Sources include the licensed Radio information Broadcasts on frequencies covering AM, Short-Wave, FM , Television, Police, Fire , Public Safety , Cellular Phones , 3G, EDGE, WiFi, Bluetooth, GPS, Radar, more…
Sources also include *unintentional* broadcasts or Emissions that do not carry information . That includes the 60 Hertz AC power distribution system or the variable frequency drive power to an electric motor in an assembly line or in a hybrid-electric vehicle. There’s the high voltage spark that ignites fuel mixture for internal combustion engines. Even a simple electric motor in a home hair dryer has spark-generating commutator and brushes as well as the myriad of small DC motors in automobiles and toys. The happy Neon Sign or ( CFL ) compact fluorescent lamp has an interrupted voltage and current flow creating the glow from within their glass tubes .
Nature’s Sources includes spectacular Lightning and its weaker cousin Electro-Static Discharge or ESD from those dry days when you rub your feet across the carpet and your finger discharges a spark to the door-knob .
Whenever there is a difference in Voltage or driving force or Potential across a path-way , then a current will flow . When that path-way includes other unintended devices, they will experience the voltage and current . Additionally the voltage and current flow action will launch a field which will radiate through space , again potentially exciting an unintended device.
So to the EMC engineer, the First Ring of Sources is all around us , made up of many different animals . One or another of them can be a threat to the normal functionality of a device. The trick is determining which ones are the likely threats to the device of choice, based upon the nature of the device as well as the likely animal acts in the First Ring when the device must operate. Happily we have Standards which specify which sources are likely to influence a device based on its nature and intended use . The Standards “alphabet soup” as I lovingly refer to it , includes contributions from many agencies of governments and industry such as SAE, IEEE, ISO , EIA, CISPR, VDE, VCC, CE , EU, CSA , … There is even a subdiscipline of EMC Engineering devoted to developing , managing and selecting Standards . I leave that to those experts. I personally prefer to look to the physics and product application aspects to guide “design for EMC” efforts.
So as the spotlight follows me stepping out of the First Ring, I know I have only tantalized you with a brief story of the Sources. You were hoping to see a lion leaping through a flaming hoop ? All in good time . First we need to visit the other 2 Rings to get the big picture before we can understand how and why to get the lion to jump, let alone thru a hoop and then with fire to boot. Patience Grasshopper ! See you soon..
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