Hi Dan,
No arguement here.
My point is that IF the regulatory agencies
allow ( however inadvertantly) products on
the market place that fail then the message
managers get is that it can't be that
important.
Incidentally it is my understanding that the
FCC Class B procedures have resulted in PC that
exceed the ClassB spec by as much as 20db.
From: "Dan Teninty"
Reply-To: "Dan Teninty"
To: "Charles Grasso" ,
Subject: RE: FW: Quality Assurance and Product Approvals
Date: Wed, 28 Nov 2001 10:15:43 -0800
Charles,
I would like to offer an explanation for EMC limits being set where they
are
and a reason for meeting or beating the limits. I agree, 0.5 dB doesn't
seem
like the end of the world and under management guidance/pressure to ship
product and produce revenue, it takes a lot of conviction to announce that
an additional turn or some tweaking of the design is required.
Those who have ever supplied avionics or anything electric to Boeing have
read somewhere in the spec that Boeing guarantees a certain level of
performance from the aircraft electrical system. Frequency stability, THC,
Voltage tolerance, etc. GREAT NEWS ! think the designers, until later in
the
spec they read the part about the stringent requirements on the "box" going
into the airplane. It seems you can't have clean power without having clean
"boxes".
The EMC limits in the standards are derived with some exceptions more or
less along the limits established long ago by MIL-STD 461/462. These limits
are well below where they would create problems in the environment, but
allow for the inevitable degradation in product performance that can occur
through component value shift, environmental conditions, and other fugitive
variables.
In order to be able to set limits for Radiated/Conducted susceptibility, an
assumption has to be made about the Radiated/Conducted emissions and how
much radiated/conducted noise there is in an intended environment.
If, "the product works fine" was the criteria for emissions, then the task
of hardening products against radiated and conducted energy would become
much more difficult.
My $0.02
Daniel E. Teninty, P.E.
Managing Partner
DTEC Associates LLC
Streamlining The Compliance Process
Advancing New Products To Market
http://www.dtec-associates.com
(509) 443-0215
(509) 443-0181 fax
-Original Message-
From: Charles Grasso [mailto:chasgra...@hotmail.com]
Sent: Wednesday, November 28, 2001 9:29 AM
To: dteni...@dtec-associates.com; emc-p...@majordomo.ieee.org
Subject: Re: FW: Quality Assurance and Product Approvals
Hi all,
I have been following this discussion with great interest
and could not resist adding my 2c.
Lest face it - EMC is nothing more than pure overhead to
any corporation. We all have experience of products that
work perfectly fine yet fail the emissions profile by
0.5dB. I will contend that this experience far outweighs the
opposite .Spinning a board or adding ferrites or adding
shielding does nothing to help our discipline reputation.
Couple that with the "twilight zone" impression of EMC
and one can easily understand why most companies
implement EMC into their process reluctantly.
I will add to that one important factor The regulatory
bodies - especially the FCC. Thanks in large part to
the new FCC Class B compliance procedure ( which
inadvertantly allows failing products into the market
place) companies are more convinced that ever that
EMC is more of an annoyance than a necessity. ( Some
exceptions duly noted..)
Unlike safety, there is no perceived benefit in squeezing
that extra 0.5db out of the emissions profile at a cost
od even .03c. The saving grace might be the immunity
standards. I have had a whole lot more help when the
design engineer actually witnesses his product doing
wierd things.
NARTE is straying in the direction of elitism. Worse than
that they now have professors offering questions for inclusion in
the NARTE exam. We need to be vigilant and keep the
infulence of the academics to a minimum. Example:
The ACES (Applied Computations Society) started a
a group with the goal of PRACTICAL applications
for comutation ..sound familiar. ?? It wasn't long before
the academics (Phds & the like) dominated the group
and turned it to a purely theoretical group - a place
to publish papers etc
Now don't get me wrong.I am all for professors that are willing to teach
and
guide and mentor. There is how ever a human tendancy
towards "creeping elegance" and we ned to ensure that the
EMC discipline does not tend in that direction.
My 2c
Charles Grasso
Ansoft Corporation
>From: "Dan Teninty"
>Reply-To: "Dan Teninty"
>To: "PSTC IEEE-EMC"
>Subject: FW: Quality Assurance and Product Approvals
>Date: Tue, 27 Nov 2001 12:11:38 -0800
>
>
>Rich,
>
>After sending you my reply, I thought that I would open it up to the
group
>for comment. I thought I would pass on the information about the NARTE
>certification for Product Safety engineers.
>
>Best regards,
>
>Dan
>
