Yes indeed. The question of limits may reduce to WHERE [a device] must
perform its function. If the only exceptional circumstance is a railway
crossing or station platform, perhaps the limit need not be raised at all.
That's what I thought when I saw the paper, anyway.
U.S. firms and marketers, meanwhile, have for consumer devices only a ONE V/m
*voluntary* immunity to contend with/ignore.
Cheers,
Cortland Richmond
KA5S
----- Original Message -----
From: Ken Javor <mailto:ken.ja...@emccompliance.com>
To: Untitled <mailto:emc-p...@ieee.org>
Sent: 11/2/2009 8:57:25 AM
Subject: Re: Where does 3V/m & 10V/m in RI come from?
As Mr. Woodgate has been tirelessly pointing out, the limits are set to
minimize complaints, but also cost. And safety isn’t an issue. If a medical
device must wok anywhere under any circumstances, then it is like the
safety-critical features of an automobile and the limits must go WAY up.
Ken Javor
Phone: (256) 650-5261
________________________________
From: Cortland Richmond <k...@earthlink.net>
Reply-To: <k...@earthlink.net>
Date: Mon, 2 Nov 2009 08:40:31 -0500
To: <emc-p...@ieee.org>
Subject: RE: Where does 3V/m & 10V/m in RI come from?
How old is the 3V/m,10V/m requirement? It was, what, 25 years ago?,
the
FCC and EPA here surveyed fields in Spokane, Washington, and concluded that
levels in the AM broadcast band were not a threat to health (never mind arcs
>from ungrounded metal structures) at ~600 V/m. But would a AED work there?
I've seen a paper regarding AED malfunction due to 16.67 Hz fields under
overheard railway power in continental Europe.
Is the standard immunity level really sufficient?
Cortland Richmond
KA5S
----- Original Message -----
From: Haynes, Tim (SELEX GALILEO, UK)
<mailto:tim.hay...@selexgalileo.com>
<mailto:tim.hay...@selexgalileo.com>
To: emc-p...@ieee.org
Sent: 11/2/2009 4:52:33 AM
Subject: RE: Where does 3V/m & 10V/m in RI come from?
Dear All,
Where does 3V/m come from? I do not know but if I run some
numbers?
E(dBV/m)=P(dbW)+14.77+G+20log(1/Distance)
How close would you put a 10kW transmitter to housing? 300m?
what antenna
gain? 6dB?
E=40+14.77+6+20log(1/300)
E=60.77-49.5 = 11.27 dBV/m
=3.66V/m
Try some other realistic examples then take a „view‰ on what
number you
would set as an immunity limit.
There will be some occasions where 3V/m is too low but do you!
make all
equipment meet higher levels or do you set levels that satisfies most
situations most of the time? Remember, most of the equipment that these limits
apply to are semi permanent as far as their location is concerned.
Somebody in the thread mentioned cars. Now cars are different.
EMC tests (as per standards) can NEVER be used for safety
certification as
the tests do not simulate the „real world‰, either in maximum potential
exposure levels, not in terms of the multiple exposures that can occur. If you
want more on this, take a look at Keith Armstrong‚s presentation at
http://www.theiet.org/events/2009/dig
sts/emcuk/armstrong-vehicles.cfm?type=pdf
Regards
Tim
************************
Tim Haynes A1N10
Electromagnet ic Engineering Specialist
SELEX Sensors and Airborne Systems
300 Capability Green
Luton LU1 3PG
( Tel : +44 (0)1582 886239
7 Fax : +44 (0)1582 795863
) Mob : +44 (0)7703 559 310
* E-mail : tim.hay...@selexgalileo.com
P Please consider the environment before printing this email.
There are 10 types of people in the world-those who understand
binary and
those who don't. J. Paxman
________________________________
SELEX Sensors and Airborne Systems Limited
Registered Office: Sigma House, Christopher Martin Road,
Basildon, Essex
SS14 3EL
A company registered in England & Wales. Company no. 02426132
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