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:[email protected]>
To: [email protected]
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/dige
ts/emcuk/armstrong-vehicles.cfm?type=pdf
Regards
Tim
************************
Tim Haynes A1N10
Electromagnetic Engineering Specialist
SELEX Sensors and Airborne Systems
300 Capability Green
Luton LU1 3PG
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This message is from the IEEE Product Safety Engineering Society emc-pstc
discussion list. To post a message to the list, send your e-mail to
<[email protected]>
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