I read in !emc-pstc that Muriel Bittencourt de Liz <[email protected]> wrote (in <[email protected]>) about 'Case: EMI from ballast (electromagnetic reactor)' on Mon, 9 Jun 2003: > >Group, > >My question is related to a curiosity related with a compact fluorescent >lamp driven by a ballast (electromagnetic reactor). I'll put a case and ask >the question. > >- In a room, I have turned on a compact fluorescent lamp driven by a ballast >(electromagnetic). The lamp power is 9W. > >- In another room (next room) I have turned on a TV. In channel 2 (VHF) I >could see two horizontal lines, about 17cm apart from each other. They keep >circulating at the TV screen in a low (subjetive) velocity. > >- Turning on and off the lamp I could realize that the lines were due to the >lamp. > >Question: Is there a relation/pattern in: > >* the distance (between the lines)
Yes, but not the physical distance in cm. We don't know whether the lines are in all fields or in alternate fields, but if they are in all fields, the height of the picture corresponds to about 16 milliseconds in time, so you can calculate the time between the pulses from that. >* orientation of the lines (horizontal, vertical, diagonal) The lines being horizontal shows that the pulses occur some milliseconds apart. If they were vertical, they would be only some microseconds apart. >* velocity of the lines in the screen (slow, steady, fast) If they are nearly steady, they are probably locked in time to the mains supply frequency, which is nearly but not quite equal to the field frequency of the TV signal. > >that I can use to diagnose the kind of EMI that's interfering with in the >TV? I suspect that the rectifiers in the lamp have no capacitors across them, so they are emitting recovery pulses into the mains wiring, which are reaching your TV either by radiation (more probable) or conduction. > -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk Interested in professional sound reinforcement and distribution? Then go to http://www.isce.org.uk PLEASE do NOT copy news posts to me by E-MAIL! This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
