[email protected],Internet writes: >RE: my request of a couple of weeks ago for EMC compliance horror >stories: > > Thanks to all who shared humorous and real horror stories. I have > shared most of them with my management. > > While the stories of good intentioned designs gone bad were helpful, I > just wish I had more accounts of manufacturers/integrators getting into > legal difficulties over non-compliance with EMC rules.
Well, while taking evening classes in the early 80's, my prof got involved with a terrible incident down in New Jersey. Seems a hospital had a high incidence of infant deaths in the intensive care ward in the maternity ward. Late at night, the alarms would go off for no apparent reason. Annoyed, the nurses would turn them off and do the rounds on foot. After some prelimenary investigation, my prof found out that a nearby tv transmitter was allowed by license with the FCC to increase their output wattage by some enormous amount after say midnight but had to reduce it prior to 6 am or some such arrangement. The cables interconnecting the nurses station to the various monitors sang like a lark with these freqs and set off alarms with induced voltages. Not sure of all the specifics except what I've related above nor the name of the hospital but they lost something like 6 kids before fixing it. Personally, the only EMC issue that's come up no matter where I've worked has to do with surges on the power grid even with compliant equipment. If you're in an industrial grid, seems as though powering up and powering down things things like an electric foundry or large numbers of air conditioning equipment can unbalance the line or phase eonough to reset equipment or cause a burst of bit errors either over the weekend or late at night. Never really zeroed in on the cause. Does tend to upset people to be running some Bellcore test over the weekend only to find the equipment in "STANDBY" mode halfway through a 3 day test. Regards, Doug
