There have been requests in the past on this forum for examples of
real world events that were EMC related, as I recall we got a few but not
many examples. In an email with Ralph he mentioned some work and an article
that he had written chronically some of these problems. I asked him for some
of his examples and he kindly sent the items below and has graciously
allowed me to forward them.
Thanks Ralph, and I hope that you enjoy them as much as I did.
Gary
-----Original Message-----
From: Ralph Cameron [mailto:ral...@igs.net]
Sent: Tuesday, June 19, 2001 6:14 PM
To: Gary McInturff
Subject: Some life threatening cases of EMI and others
Gary:
These cases were reviewed in an article I wrote about 14-15 years ago. Most
incidents could happen tomorrow and came from a record of emi cases reported
to all Canadian district offices of what used to be called Communications
Canada. The reports covered a planned three month monitoring period during
which time ther were 439 emi related reports and another 242 cases of
swamping
( RF overload of TV, radio etc.) If you consider that Canadian incidents
represented about 8% of the total number of incidents in the U.S. at that
time, it may help to place the occurrences in perspective.
Since that time, Industry Canada has not recorded domestic problems or
complaints due to a lack of immunity ( radiated or conducted) but do have
an advisory bulletin specifying field strengths communication transmitter
owners cannot exceed. These limits are taken from the EU requirements for
electronic equipment radiated immunity . Not surprisingly, I have found at
least 95% of interference cases have been resolved not by increasing
radiated immunity but, by reducing or eliminating most of the conducted
component That's why I believe the simple expedient of designed in conducted
immunity levels the playing field for all consumers and removes the
nuisance of trying to find a solution, particularly, after sale.
Examples:
London Ont. A vhf broadcast radio link , owned by a commercial broadcast
station , operating in a shopping mall, disrupted electronic weigh scale
operation. False and incorrect weights and prices were displayed while the
link was operating.
Peterborough Ont. A CAT scan medical device's operation was disrupted by
transmissions from a new FM broadcast transmitter.
Brampton ON Radio frequency plastic sealing equipment located in close
proximity to a neighbouring paint operation seized control of the six foot
paddles stirring the vat of paint to the point where the shaft broke away
from the motor , burst through a water tank and embedded itself in the
factory wall.
Toronto ON A hospital heart monitoring system displayed erroneous readings
when the hospital radio despatch system was operated.
Toronto ON A Federal government's computer system would "crash" when a
nearby chiropractor operated his diathermy ( radio frequency generator )
machine.
Edmonton Ab The telephone company lost billing data from their computer
system which was attributed to the operation of a nearby private commercial
radio despatch system.
Calgary Ab An amateur radio operator's transmissions were heard in the
recording equipment of a professional recording studio. Until the problem
was resolved, the studio lost money on their operations.
Grande Prairie Ab When a hospital's diathermy was used, the hospitl alert
system would occasionally issue a a 'code 9' alert, in error. The diathermy
also affected the physiotherapist's treadmill by accelerating the motor
control mechanism.
Grande Prairie Ab The mobile cranes on a logging company's railway had a
collision avoidance system installed in each crane. Radio transmissions
would occasionally defeat the protection offered by these systems.
In Ottawa ON Ontario Hydro Electric Power Commission reported that Oil
fired generating stations' control equipment on oil fired generators was
affected by operation of nearby mobile radio equipment .
Gas monitors, required for confined space atmosphere, continuous monitoring
of toxic/ explosive gases and oxygen were found to give false alarms in 7
of 8 tested near UHF , narrowband ( 466Mhz ) transmissions and one had
problems from 49Mhz narrow band signals.
Because many amateur radio operators reside in urban areas, their HF
operations ( covering 1.8-144Mhz ) have been demonstrated to affect the
following . In some instances they could cause harmful effects:
Intravenous pump in hosptial room went into the reset ( fail safe) mode when
a 2W(144Mhz) handy talky was operated any closer than six feet from the
pump. A manual reset is necessary to continue pump function. Although this
happened on 26 separate occasions and I reported it to our Federal Dept of
Health, they had the manufacturer investigate the problem and couldn't
duplicate it.
VCR and kitchen mantle radios generate objectionable noise when NOT powered
Output transistor junctions make good detectors when energy is power line
conducted.
Garage door openers operate intermittently due to presence of RF many Mhz
removed from their intended frequency of operation. ( Remember Pres.
Nixon's Air Force One setting of many west coast garage door openers every
time he decided to vacation in his California ranch).
Just last year, a commercial aircarft undergoing maintenance at an Air
Canada hangar in Montreal was suspended from a crane while undergoing
mechanical as well as radio maintenance.
Upon installation of the SSB HF radio, the maintenance personnel operated
the radio within the hangar to discover that the crane began to lift the
aircraft without human intervention. Only a quick thinking oeprator
prevented serious consequences.
While not life threatening , but adding a aura of mystique, was one I
personally investigated in a home located about 1/4 mile from a broadcast
transmitter. It was a "talking " card table, caused by rectification in a
rusty leg joint. After getting over the shock of that the homewoner
commenced to tell me that that was nothing his neighbour " had a talking
waterbed". Yes, thermostats can rectify. !!
There are many more similar cases to the above and all involve radio
sensitive equipment. Fifteen years ago, electronic test equipment
manufacturers were designing immunity into their products as the ambient was
estimated at one volt conducted and more than one volt radiated.
I wonder what it is today?.
Ralph Cameron
EMC Consluting and Suppression of Consumer Electronic Equipment
(After sale)
----- Original Message -----
From: "Gary McInturff" <gary.mcintu...@worldwidepackets.com>
To: "'Ralph Cameron'" <ral...@igs.net>
Sent: Tuesday, June 12, 2001 10:35 AM
Subject: RE: Wireless Network Issues
> Ralph,
> Readers have in the past, requested examples of EMC problems, I
> wonder if you could share some of your experiences you mention in the last
> paragraph.
> Gary
>
> -----Original Message-----
> From: Ralph Cameron [mailto:ral...@igs.net]
> Sent: Monday, June 11, 2001 8:11 PM
> To: kyle_cr...@dell.com; emc-p...@majordomo.ieee.org
> Subject: Re: Wireless Network Issues
>
>
>
> Kyle:
>
> Take a look at www.Intellon.com . They detail a link to some of the
> problems associated with proximity of Bluetooth devices to 802.11 LAN
> specs. These are claimed to be potential interference problems related to
> hop frequency differences in the two spread spectrum systems.
>
> There is also concern with the power line conducted control systems and
the> Continental Automated Building Associated attempted to address some of
the
> issues related to compatibility during their conference held at the end of
> May. There are some 26 different standards all independantly developed
> which I'm sure is enough for a statistical study of the problem.
>
> There have been several papers on lack of EMC in hospitals - some
> originating from McGill University in Montreal. The main problem there
seems
> to be lack of any emc equipment requirements ( although changing due to
> liability ) and the solution has been to isolate the areas containing the
> radio sensitive equipment.
>
> Tha Radio Advisory Board of Canada's EMC sub committee did address some
> concerns toward cable TV radiation and possible effects on some aircraft
> frequencies. With those problems largely overcome by regulating the cable
> operators , another issue has arisen and that could affect radio aids to
> navigation and it may have to do with radiation from home wiring above
2Mhz
> . This is conceivable with ever increasing data rates and unshielded
wiring.
>
> When I was chairman of the RABC EMC committee for a couple of years, there
> were many instances of life threatening incidences related to lack of EMC.
>
>
> Ralph Cameron
> Electromagnetic Compatibiliy Consulting and Suppression of Consumer
> Electronics
> ( after sale)
>
>
> ----- Original Message -----
> From: <kyle_cr...@dell.com>
> To: <emc-p...@majordomo.ieee.org>
> Sent: Monday, June 11, 2001 5:23 PM
> Subject: Wireless Network Issues
>
>
> >
> > Hi All,
> > I am currently researching wireless intereference issues for a
> > project and I was wondering if anyone could answer a few of my
questions.
> > First off, any links to information that deals directly with wireless
> > interference on airplanes or in hospitals would be appreciated.
Secondly,
> I
> > am curious how similar cell phone wireless technology is to wireless
> network
> > technology(Wi-FI), from an EMI standpoint. The reason I ask is that I
can
> > find a lot of information about cell phone intereference, but I have
found
> > nothing about wireless network interference. I am still learning a lot
> > about this, so any information that you could provide would be
> appreciated.
> >
> > Thanks,
> > Kyle
> >
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