Yes, what Earl Morse said is very important! Always keep in mind we have to
carefully take care of BOTH signal trace and return path. If the reference plan
is solid, the return path would automatically make it's way to form a least
loop area with signal trace. (Why? least loop area - least
Another aspect to consider is the measurement of magnetic fields using a
loop antenna at frequencies much lower than 30 MHz. These measurements are
not performed on a typical OATS and a 1-4 meter scan height is not required.
Thus we do not need to dig a hole for the rest of the antenna (though
Another factor is the power system.
In US/Canada, multi-grounded neutral WYE systems are common, as are
single-phase primaries (with grounded neutral returns) on rural roads.
Elsewhere, delta systems are used, which react less violently in case of
a phase fault.
Regards,
Frank McCaughey
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6:30 - 7:15PM Social Time
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The distance of one sixth lambda comes from empirical data taken from a
Hertzian dipole antenna. In his book Introduction to Electromagnetic
Compatibility ISBN 0-471-54927-4, Clayton Paul writes: The point where the
1/r3 (cubed) and 1/r2 (squared) terms become insignificant compared with the
We design oscillators out of discrete components to meet the minimum drive
requirements.
If a can oscillator is used, RC terminations and power filtering is usually
required to keep the harmonics from flowing into other ciruits.
Regards,
Wolf Josenhans
Allen Tudor
The number one problem with PCB board routing that we encounter that can be
attributed to the layout personnel is:
Routing high speed signal traces without regard for return current paths.
Either the signals are routed across splits in the reference plane or the
signal switches layers and the
Please, could anyone give me some advice regarding the fiber optics?
As I know the IEC 825-1 (and CFR Title 21 for US) and IEC 825-2 are used as
reference lasers safety standards.
What' s the procedure for certification process of a product (certified with
IEC 65) which incorporate fiber optics
Here is the actual text:
(2) At frequencies below 30 MHz,
measurements may be performed at a
distance closer than that specified in
the regulations; however, an attempt
should be made to avoid making measurements
in the near field. Pending the
development of an appropriate measurement
procedure
John, thanks for the reference. It gave a good historical perspective.
It would seem the use of dBv (.775 V reference) and dBV (1.0 V
reference) created enough confusion for the pro audio industry to
introduce the new unit dBu. While not an active observer in the pro
audio scene, I would
I don't see this issue as one of whether manufacturers meet the standards.
It is more one of whether the standards are adequate.
Now the task becomes one of defining adequate.
We've all see the hatchet jobs that the press or special interest group will do
when they get on a mission.
I'm not sure
In a message dated 1/21/00, John Boucher writes:
What I'm really wrestling with is whether we need to be concerned about
power
line cross / induction issues outside of North America.
John:
I too have heard the argument that AC mains wiring outside of North America
is different, and
--
From: Paul Paroff
To: Darrell Locke
Subject: RE: Correlating sine sweep with random vibration
List-Post: emc-pstc@listserv.ieee.org
Date: Friday, January 21, 2000 9:22AM
To add my voice to the many, there is no agreed upon correlation between
sine sweep and random vibration. A paper
All:
Regarding UL 1950 section 6.6 Protection against overvoltage from power line
crosses: this requirement is peculiar to the UL / CSA versions of the IEC 950 /
60950 standard.
1) Is this because (as I've heard) countries other than US / Canada do not route
telecommunication wiring on the
Just a side note that Mr. Montrose will be speaking at the Feb. 10th meeting of
the Orange County Chapter of the IEEE EMC Society. If you would like to attend
the presentation, contact me at the number shown below.
Regards,
Randy Flinders
Chairman
Orange County Chapter
IEEE EMC Society
Hello group.
I substantially agree with the comments of Allen Tudor
Don Umbdenstock. My own view is :
I believe the 40 dB / decade (of distance) is a questionable approximation
for extrapolating the measurement antenna location being reduced from 10
meter to 3 or possibly 1 meter in an
Dave,
Here's a link which explains some of the dB variations including dBu.
-http://www.music.mcgill.ca/~martin/textbook/electronics/03.html
John Juhasz
Fiber Options
Bohemia, NY
-Original Message-
From: Dave Wilson [SMTP:dwil...@babtps-us.com]
Sent: Thursday, January 20, 2000 4:16
The difference is the transition region.
Simplified expression of transition region is lambda/2pi. At some number of
wavelengths above this point the propagation roll-off is linear, i.e., 20
dB/decade. Well below 30 MHz, near field phenomena are encountered. Also,
antenna configurations may
Sounds to me as if they're being doubly cautious here. First they warn you
not to make measurements in the near field. Then they use the 40dB per decade
extrapolation factor to account for measurements taken in the near field (or
perhaps the cross-over point between the near and far
Question:
According NFPA 79 15.3: control wiring must be AWG 16 or AWG 18. Is this
also applicable for control wiring which is acting on safe voltages (60
V d.c.,
42 V a.c., 240 VA).
Bert Planting
ASMLattachment: Bert.Planting.vcf
Dave,
dBu is dB relative to .775 volts. dBu decibels referred to the voltage
equivalent of 0 dBm into a 600 ohm load. 0 dBu = 0.775V =
2.2 dBV.
I hope this helps
John Radomski
Compliance Engineer
Inter-Tel Integrated Systems
Another source may be the ESD Association. Two standards that may apply (as
I have never seen nor used them) may be EOS/ESD S5.201994 and ESD-DSP
10.1-1999 (draft)? There web site address is www.eosesd.org
Good Luck!
-Original Message-
From: Christian Martí [mailto:cma...@efinet.com]
The most common mistakes carried out on PCB are:
1 Use 2-layer instead of multi-layer boards
2 Permit high F clocks to go trough long traces ( 4 Mhz)
3 Place connectors all over the surface instead of corner or edge
4 Let input and out lines of analog and power circuits run unfiltered to the
There are a number of good books available on the subject. There are two
that I would recommend to start with.
Printed Circuit Board Design Techniques for EMC Compliance
Mark I. Montrose
IEEE Press
ISBN 0-7803-1131-0
IEEE Order Number PC5595
Noise Reduction Techniques in Electronic Systems
Hello Group:
The State of Vermont has a labeling law becoming effective 3-1-2000 which
requires products which contain mercury-containing components to be labeled
as such and direct the customer/servicer to properly dispose of such
components at the time of replacement.
I understand that
Most of the mistakes are by the design engineers and not the pcb designers.
The mistakes are:
* Mixing of I/O devices with clocks, processors and similar noisy
digital devices
* Inadequate power/ground isolation of noisy digital devices
* Inadequate I/O filtering
*
Hi,
It is true that 4.4.4 allows a mechanical or electrical enclosure not
serving as a fire enclosure to be HB when it is located externally to a fire
enclosure.
Phones and video games could be HB for this reason, however they could also
have been tested as being a limited power source under
Dear List-Members,
I am requesting information/opinions/etc. on the following:
When circuit boards are designed, what are the common mistakes that the
circuit board designers make regarding EMC (multi-layer boards in
particular)?
You can respond to me directly but I would prefer a response
Dave,
I have always seen this used for micro, as in dBuV = decibel microvolts.
It may also stand for decibel units. If so, a unit is most likely 1 volt
rms, a common unit in professional audio. The formula would be 20 X
LOG(input voltage/reference voltage), with LOG referring to LOG 10.
Scott
As a supplement to the recent lead thread, the latest issue of
Electronics Manufacturing Products (a UK trade paper) has a
minor headline It's tin-silver-copper. The Printed Circuit
Interconnect Federation and International Tin Research Institute
have apparently chosen to recommend Sn-Ag-Cu
Tha paragraphs are from FCC Part 15.
===
-- Forwarded by Robert E. Heller/US-Corporate/3M/US on
01/21/2000 05:49 AM ---
Robert E. Heller
01/21/2000 05:49 AM
Terawave Communications a leading manufacturer of Intelligent Wave Division
Multiplexing (IWDM) equipment, targeted at local access networks, is seeking
a Compliance Engineer.
The successful candidate will be expected to lead the compliance approvals
on all of Terawave products, which will
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