ESD Gun targets

[drcuthbert]

Jim,

the Pelligrini Target spec in EN61000-4-2 is quite a challenge to meet. The 1
dB insertion loss delta from DC to 4 GHz to be exact. The simulation of my
proposed PCB design shows that it can meet the spec and I have the equipment
to verify this.

I will build a few targets. Perhaps a few of you would like a target to use
and to provide feedback. Who wants a target? Step right up and get your red
hot Pelligrini targets!

   Dave Cuthbert
   Micron Technology


From: Jim Ericson [mailto:jde...@nas.com]
Sent: Saturday, May 03, 2003 5:09 PM
To: emcpost
Cc: drcuthbert
Subject: Re: ESD Gun verification


Dave:

Yes.  The current-sensing transducer that I built (Pelligrini Target) is
per the Annex B drawings in EN 61000-4-2:1995 + A1:1998 +A2:2001.  It has
five paralleled 240 Ohm resistors arranged radially around the oscilloscope
side to give 48 Ohms.  On the ESD Gun side are twenty-five radially spaced
50 Ohm resistors to give 2 Ohms.  Transconductance is 1 Amp/1 Volt into 50
Ohms.

The present Standard requires a minimum 1 GHz bandwidth oscilloscope.

I use a Pasternak Model PE7002-30 (DC to 2 GHz) 1 Watt Attenuator between
the Pelligrini Target and the scope (voltage ratio of 32).  The oscilloscope
is a Tektronix 7104 with 7B10 time base, and a 7A26 dual-trace amplifier.

I'll email a couple of photos to you (offline), and copy Mr. Pommerenke and
Mr. Kinney.

Regards,
Jim Ericson
Acme Testing Company
j...@acmetesting.com


- Original Message - 
From: drcuthbert drcuthb...@micron.com
To: 'Jim Ericson' jde...@nas.com
Sent: Friday, May 02, 2003 8:07 AM
Subject: RE: ESD Gun verification


 Jim,

 I simulated this. I am assuming the circuit is a 2 ohm resistor to GND. If
so, the series inductance must be 0.1 nH for the 2 ohm resistor. Does this
sound right? I can do this with 25 paralleled 49.9 ohm resistors arranged
radially around the input (discharge) point.

Dave Cuthbert
Micron Technology

 -Original Message-
 From: Jim Ericson [mailto:jde...@nas.com]
 Sent: Thursday, May 01, 2003 11:50 PM
 To: emcpost
 Subject: ESD Gun verification



 John:

 I faced the same problem about six years ago.  I needed to do
verification
 in between the expensive annual calibrations.  I first explored the
option
 of buying a Pelligrini Target.  As I recall, the quotes I received were
 around $2000.  That seemed outrageous, so I decided to build one myself.
 I'll bet it took me at least 3 days to make sense of those goofy
mechanical
 drawings in 61000-4-2.  If only they had included a photograph or good
 cross-section in the Standard!

 Anyway, I finally figured it out, translated the drawings into something
 understandable by a U.S. machine shop, and got all the brass parts
 fabricated locally.  It took several in-process consulting sessions with
the
 machinist, but I finally got all the brass parts done for around $300.
 Then, I purchased a $25 silver electroplating kit.  It was like Science
Fair
 time in my workshop!  Some hours of painstaking soldering later, the
target
 was completed.  I mounted it over a specially-drilled hole in the brass
wall
 panel of our anechoic chamber (you need a Faraday Cage of some sort, and
 this seemed the easiest).  I did a quick check using our Tektronix 1 GHz
 analog oscilloscope ... and the risetimes and overall waveforms measured
 within spec!  Then, I sent the target to Haefely-Trench for a
calibration
 (against their standard Pelligrini target).  The results were very, very
 close.

 Having performed many verifications at this point, my advice (if you want
 fairly accurate and repeatable results):

 1.Make (or buy) something resembling the 61000-4-2 target.
 2.Use a Faraday Cage.
 3.Be aware how important the POSITION of the ESD Gun Grounding Strap
is
 to these measurements ... especially to risetime measurements.  I always
 take a photograph of the setup, including the shape of the Grounding
Strap
 and where it is attached.  If you don't do this, you'll get pretty wild
 variability between verifications.
 4.Even a 500 MHz oscilloscope would probably be OK for verification.
 Just make certain that all setup parameters (including Ground Strap
 placement) are EXACTLY the same each time.  That way, if the GUN happens
to
 change, you'll at least know what to do next.

 Give me a call if you'd like a photo.

 Good luck!

 Jim Ericson
 Quality System Manager/Sr. EMC Engineer
 Acme Testing Company
 Acme, WA.
 888-226-3837
 j...@acmetesting.com

 - Original Message - 
 From: John Harrington jharring...@f2labs.com
 To: emc-p...@majordomo.ieee.org
 Sent: Thursday, May 01, 2003 11:45 AM
 Subject: ESD gun verification


 
  Hello All
 
  Does any one have a quick and dirty (and hopefully cheap) way to verify
 the
  performance of an ESD gun.
 
  Please, no one suggest building the current sensing system described in
 the
  back of IEC 61000-4-2.  I don't understand the drawings let alone have
the
  workshop or materials to consider it.  Although

PCB checklist

[drcuthbert]

Here is a PCB checklist at http://www.x
linx.com/xlnx/xil_prodcat_product.jsp?title=si_pcbcheck

Here is another link at xilinx: http://
ww.xilinx.com/xlnx/xil_prodcat_landingpage.jsp?title=Signal+Integrity

   Dave Cuthbert
   Micron Technology


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RE: Check list for PCB Layout

[drcuthbert]

I will send a list of three good books on these two connected subjects (signal
integrity and PCB EMC) in a day or two. Basically and briefly here is my
viewpoint:

For signal integrity you must be familiar with transmission lines; how to
visualize signal propagation along a T-line and how to perform simple
simulations. I use the free evaluation version of MicroCap-7 for T-line
simulation. This really helps in predicting what will happen or to explain
what strange things you are seeing in your PCB. So, think like an
electromagnetic wave. Maintain a constant impedance through the signal path.
Terminate either the source, the load, or both ends of the T-line if the path
is 1/6 the signal rise time. And most importantly, use a power plane and a
GND plane. This means a minimum of 4 layers. If you are doing low-cost
consumer designs you will be pressured to minimize the number of layers. This
is where an experienced signal integrity engineer can save you money. 

For PCB EMC don't design the PCB to be an antenna. You might want to study
antennas. Think of monopole antennas (daughter cards) and loop antennas (PCB
traces and IC lead frames). Minimize the height of daughter cards and
components. These radiate by common mode current. Minimize the loop area of
the loop antennas. These radiate by differential mode current. Use PCB's
with a power and a GND plane. This means at least 4 layers. Don't split planes
unless you understand what the implications are. These form slot antennas and
signal integrity problems if there is RF current trying to flow across the
slot.

Bringing DUT cables out of an enclosure is a great way to fail EMI tests. It
takes only about 1 mV of RF on a 1/4 wavelength DUT cable to fail EMI tests.
Any DUT cables that are shielded need the shield to be 360-degree terminated
to the conductive enclosure. This ensures that the cable and enclosure have
zero RF potential between them. No RF potential means no RF current on the
antenna. 

   Dave Cuthbert
   Micron Technology


From: Cortland Richmond [mailto:72146@compuserve.com]
Sent: Friday, April 25, 2003 5:18 PM
To: tkrze...@genius.org.br; ieee pstc list
Subject: Re: Check list for PCB Layout



 I would like to create a check list in order to help designers and PCB
routers of my company to improve their design / EMI and SI. 

This is one of the things we get paid to do, assuming anyone is
paying us at all. For this and other reasons given by those who've
already answered your request, it is something you will usually have
to come up with on your own, or pay someone to give you. This last
can often be done by paying them to give your board designers a
seminar on signal integrity; the printed materials supplied with
the course almost always have some kind of check list included, or
at least, rules you can make into one.

Luckily, it's not hard to come up with a check list that will make
a difference in your boards. In its simplest form, it can be nothing
more than a list of everything done _wrong_ over the past few years,
with Do not ... in front of it. 

For example,
Do not 
interrupt ground planes.
delete return traces.
leave out ground vias when changing layers.
run high speed clocks on board edges.
share ground traces and connector pins between critical signals.

and so on.

The physics is fairly direct. Getting your check list implemented, that
can be difficult, and I've often thought a seminar on the politics of
EMC would be as valuable as one on its physics.

Good luck!


Cortland


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RE: Thermocouple glue

[drcuthbert]

I sometimes use a small piece of Kapton tape to hold a thermocouple.
 
Dave Cuthbert
Micron Technology


From: John Allen [mailto:john.al...@era.co.uk]
Sent: Wednesday, April 23, 2003 10:29 AM
To: IEEE EMC/Product Safety (IEEE, EMC/Product Safety)
Subject: RE: Thermocouple glue



Hi Folks

Most of the replies so far seem to indicate the use of permanent adhesives
- which means the thermocouples could be difficult to remove and re-use.

Therefore, since these items tend to be too expensive to be considered as
throw-away items, does any one have suggestions for adhesives which wil
stick reasonably well but will then allow the thermocouples to be removed
fairly easily and without damage?

Regards

John Allen
ERA Technology Ltd


From: Constantin Bolintineanu [mailto:cbolintine...@dsc.com]
Sent: 22 April 2003 15:22
To: 'Ned Devine'; IEEE EMC/Product Safety (IEEE, EMC/Product Safety)
Subject: RE: Thermocouple glue



I am using LOCTITE 416 - Net wt. 1 OZ.(Part No. 41650) along with the
LOCTITE ACCELERATOR 7452 (Part No. 18637) net. WT.0.70 OZ and works well for
Thermocouples AWG 30. (5-8 seconds)

Respectfully yours,
Constantin

Constantin Bolintineanu P.Eng.
DIGITAL SECURITY CONTROLS LTD.
3301 LANGSTAFF Road, L4K 4L2
CONCORD, ONTARIO, CANADA
e-mail: cbolintine...@dsc.com
Telephone: 905 760 3000 ext 2568
Fax: 905 760 3020

DISCLAIMER: This e-mail message may contain privileged or confidential
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From: Ned Devine [mailto:ndev...@entela.com]
Sent: Wednesday, April 16, 2003 9:11 AM
To: IEEE EMC/Product Safety (IEEE, EMC/Product Safety)
Subject: Thermocouple glue



Hi,

In the past I have used Henkel Sicomet 77 to adhere thermocouples.  I
just tried to reorder some and was told it has been discontinued.   

Does anyone have a recommendation on a replacement?

Thanks

Ned Devine
Entela, Inc.
3033 Madison Ave. SE
Grand Rapids, MI  49548

Phone: 616 248 9671
Fax: 616 574 9752
e-mail: ndev...@entela.com
www.entela.com 
Entela, Inc. A Certified Woman Owned Business 




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RE: Charge level of rechargeable batteries

[drcuthbert]

Is the discharge requirement so that the unit cannot power up (burn up in
shipping)? I have purchased a couple of items that had plastic tape inserted
between the battery contacts and the battery connector. Is this acceptable?

  Dave Cuthbert
  Micron Technology


From: don_borow...@selinc.com [mailto:don_borow...@selinc.com]
Sent: Wednesday, April 23, 2003 8:29 AM
To: emc-p...@majordomo.ieee.org
Subject: Re: Charge level of rechargeable batteries




I don't know about any regulatory or safety aspects, but it would be
difficult to have all batteries leave the factory uncharged. Specifically,
lead-acid and lithium cells need to have at least a minimum level of charge
or they will be damaged. NiCd and NiMH cells are OK with no charge.

Donald Borowski
Schweitzer Engineering Labs
Pullman, WA





raymond...@omnisourceasia.com.hk@majordomo.ieee.org on 04/15/2003 07:59:39
AM

Please respond to raymond...@omnisourceasia.com.hk

Sent by:owner-emc-p...@majordomo.ieee.org


To:emc-p...@majordomo.ieee.org
cc:
Subject:Charge level of rechargeable batteries







Dear All,

In the past, the rechargeable batteries accompanying with product must
not be charged before leaving manufactory for certain safety
regulation.  Recently, I notice that the accompanying rechargeable
batteries are charged to certain level.  At least, it can be used to
check the product before they pay for the product.  Can someone tell
the safety requirements about this and any changes recently.

Thanks,

Raymond Li
Omni Source Asia Ltd.





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RE: Low signal switching

[drcuthbert]

Some of these attenuators use wiping contacts- self cleaning. If there are any
microwave switches like that they will last longer during dry switching.
There is one SA I know of that has an attenuator exercise cycle. When the unit
is powered up it runs the attenuator through several cycles to clean the gold
contacts. 

  Dave Cuthbert


From: Ken Javor [mailto:ken.ja...@emccompliance.com]
Sent: Monday, April 21, 2003 5:20 PM
To: drcuthbert; 'djumbdenst...@tycoint.com'; emc-p...@majordomo.ieee.org
Subject: Re: Low signal switching


I can certainly suggest a solution, although it would take a bit of research
to totally determine the answer.  There are any number of spectrum analyzers
and EMI receivers out there with switchable front-end attenuators.  An HP
8566 has a noise floor of -135 dBm with a 10 Hz bandwidth and full video
filtering. An NM-37/57 has a much lower noise floor and these things have
been around for close to forty years, with no problems that I know of with
the attenuator switches fouling.

So any of the manufacturers of EMI receivers spectrum analyzers should know
what swtiches to buy.

I checked out Mini-Circuits:

http://www.minicircuits.com/

and the only amplitude related specs there were insertion loss and vswr.

 From: drcuthbert drcuthb...@micron.com
 Reply-To: drcuthbert drcuthb...@micron.com
 Date: Mon, 21 Apr 2003 14:58:57 -0600
 To: 'djumbdenst...@tycoint.com' djumbdenst...@tycoint.com,
 emc-p...@majordomo.ieee.org
 Subject: RE: Low signal switching
 
 
 Don,
 
 I have encountered this problem with low-level signals. It seems to vary
 greatly from manufacturer to manufacturer (the company we had the best
results
 with went out of business). When the contact(s) became dirty I would run a DC
 current and clean it. The problem would quickly return and the only real fix
 was to replace the relay. One to two years of life was typical. I also would
 like to know a good solution.
 
 Dave Cuthbert
 Micron Technology
 
 
 
 -Original Message-
 From: djumbdenst...@tycoint.com [mailto:djumbdenst...@tycoint.com]
 Sent: Monday, April 21, 2003 11:28 AM
 To: emc-p...@majordomo.ieee.org
 Subject: Low signal switching
 
 
 
 Hello Friends,
 
 I have an application in which I would like to switch system signals on coax
 cables. One system is 80 to 1000 MHz, the other is 1-2 GHz.  I have found
 coax switches by Narda, DB Products and Dow Key. Dow Key indicates that the
 signals should be above -20 dBm to ensure that contact resistance doesn't
 cause a problem.  The others do not spec or address low signal issues. My
 branches operate at -35 dBm, 0 dBm and 50 dBm.  The 2 higher values are not
 a problem, just the -35 dBm.  Are there other companies that you are aware
 of that make 50 ohm coax switches that are specified to operate at low
 signal levels?  Other ideas?
 
 Best regards,
 
 Don Umbdenstock
 Sensormatic
 
 ---
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RE: Low signal switching

[drcuthbert]

Don,

I have encountered this problem with low-level signals. It seems to vary
greatly from manufacturer to manufacturer (the company we had the best results
with went out of business). When the contact(s) became dirty I would run a DC
current and clean it. The problem would quickly return and the only real fix
was to replace the relay. One to two years of life was typical. I also would
like to know a good solution.

   Dave Cuthbert
   Micron Technology




From: djumbdenst...@tycoint.com [mailto:djumbdenst...@tycoint.com]
Sent: Monday, April 21, 2003 11:28 AM
To: emc-p...@majordomo.ieee.org
Subject: Low signal switching



Hello Friends,

I have an application in which I would like to switch system signals on coax
cables. One system is 80 to 1000 MHz, the other is 1-2 GHz.  I have found
coax switches by Narda, DB Products and Dow Key. Dow Key indicates that the
signals should be above -20 dBm to ensure that contact resistance doesn't
cause a problem.  The others do not spec or address low signal issues. My
branches operate at -35 dBm, 0 dBm and 50 dBm.  The 2 higher values are not
a problem, just the -35 dBm.  Are there other companies that you are aware
of that make 50 ohm coax switches that are specified to operate at low
signal levels?  Other ideas?

Best regards,

Don Umbdenstock
Sensormatic


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RE: path-loss equation

[drcuthbert]

George,
 
path loss is independent of frequency. The reason frequency appears in this
formula is that path loss is the loss between two dipole antennas. The
capture area of a dipole (about 1/8 sq wavelength) drops by a factor of 4 with
each doubling of frequency (20LOGF/f). Anyway, the standard path loss equation
makes it a simple matter to find the antenna gain(s) required. And you are
right that your formula is close for free space conditions (I get 94 dB path
loss using another method).
 
For conditions that result in 1/R^3 use 30LOG rather than 20LOG. For 1/R^4 use
40LOG rather than 20LOG. 
 
  Dave Cuthbert
  Micron Technology
 

From: George Stults [mailto:george.stu...@watchguard.com]
Sent: Thursday, April 10, 2003 9:24 AM
To: emc-p...@majordomo.ieee.org
Subject: path-loss equation



Hello Group,

 

I came across an equation for radiated signal path-loss (attenuation).  I'd
like to check my understanding of its meaning.  The equation is

 

Attenuation  =  37 + 20 log (F MHz) + 20 log (D miles).

 

So for instance, If I wanted to know the distance for a radiated signal (2450
MHz) to be attenuated by 100db, the calculation would be

 

[100 - 37 - 20 log (2450)] / 20 = log (D miles) and the answer in miles would
be  0.5765 miles...  or 3044 feet.  

 

My assumption is that this equation gives an answer for line-of-sight (1/R^2)
type of loss.I'd like to estimate loss for a cluttered environment that
approximates 1/R^3 or 1/R^4. My question is, how could this equation be
modified for that purpose, or is there some other standard equation to
estimate loss at a given frequency in varying environments, either in meters
or feet etc.   I have tried a few ideas, but numeracy fails me on this
occasion.

 

Thanks in Advance.

 

George Stults

WatchGuard Technologies Inc.

RE: PC EMI

[drcuthbert]

Good points. Perhaps the units to be tested need to be given a simulated
shipping ordeal prior to testing. Dropping, shaking, heating, and cooling.
 
   Dave Cuthbert

From: Gary McInturff [mailto:gary.mcintu...@worldwidepackets.com]
Sent: Wednesday, March 26, 2003 8:35 AM
To: lfresea...@aol.com; randall.flind...@emulex.com;
emc-p...@majordomo.ieee.org
Subject: RE: PC EMI


Derek,
While I have never seen the extent of failure (amplitude)  you're talking
about I have run into a tower or two that didn't comply. It was some few dB
out hither and yon. (The monitor was the next biggest concern but I had few
troubles with those, although Gateway went through a bad period for awhile
some years ago). I was able to take care of it in these few cases by cleaning
all of the mating surfaces, resetting all the cards in the bus, and tightening
the enclosure fasteners. Given everything else you've been through I suspect
your tried that already and I suppose there is no reason you should have to do
that. But one of the things that isn't addressed is how well these things
travel when shipped or when people add internal cards etc. Joints loosen etc.
Obviously, that's not the complete answer by any stretch, but it got me
what I needed - a system that met class B. Then I left the unit at the test
lab, and spent a little time refurbishing it every so often. 
Design wise, I've always found the I/O card slots to be the most
problematic. They really aren't designed very well from an attachment
perspective. I've usually had a couple of small indents added to the card face
plate, in the center of the face plate to provide a little positive contact.
Typically they hook into a slot on one end and have no real contact force from
that end to the end which screws into the chassis. If the face plate, or the
chassis sheetmetal has a bow into a relatively large seem is left open. I was
dealing with gigabit network interface cards (GNICs) at that point and they
have some high frequency stuff very close to this interface.
Basically even a good chassis can go bad if it isn't maintained over time
or after shipping. I'm not suggesting this is the overall solution to the
problem that has your snuggies in an uproar, :) but it may help on the
onsey-twosey case for your clients in the lab.
Gary
The note below is probably better and worth 2 cents so this must then be
the 1 cent version.



From: lfresea...@aol.com [mailto:lfresea...@aol.com]
Sent: Tuesday, March 25, 2003 5:59 PM
To: randall.flind...@emulex.com; emc-p...@majordomo.ieee.org
Subject: Re: PC EMI


In a message dated 3/25/2003 5:10:12 PM Central Standard Time,
randall.flind...@emulex.com writes:





I am sure you also addressed this but since I have 2 cents to add...

A front-end overload condition on the receiver/analyzer, or an overload at
the pre-amplifier, can cause errors in measurement that may seem
transparent.  A local transmitter could be overloading your measurement
system and increasing your emissions readings

Again, take it at what it is worth!  (2 cents)





Hi Randy,

Where I live, lucky to have electricity :-)

When I set my software up, I played with attenuators to make sure that with my
signal path, I have at least 20 dB over the Class A limit before I get into
any of the signal measurement chain elements either going into compression or
saturation.

When ever I get an outage like this, I always add 10 dB in the signal path and
remeasure... Just to make sure the two curves track.

Cheers,

Derek. 

RE: NEC-2 simulations

[drcuthbert]

Tim,
what is CEM? 

   Dave Cuthbert


From: Wan Juang Foo [mailto:f...@np.edu.sg]
Sent: Thursday, March 27, 2003 2:34 AM
To: drcuthbert; emc-p...@majordomo.ieee.org
Subject: Re: NEC-2 simulations



I use NEC-2 in a limited way.

Good to hear that there are others on the PSTC list that does that. :-)

BTW, are there any guys out there that work with CEM?

Tim Foo






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RE: Demonstrating compliance with Human Exposure to EMF requireme nts

[drcuthbert]

Charlie,
1/2 lambda is 7.5 cm at 2 GHz. At this distance the field strength is 67 V/m
assuming far field. So, no near field calculations are needed as long as the
distance is greater than approximately 10 cm. The actual field is not that
difficult to calculate anyway. Or, just use NEC to simulate the field strength.

  Dave Cuthbert
  Micron Technology


From: Charles Blackham [mailto:cblac...@airspan.com]
Sent: Wednesday, March 26, 2003 9:49 AM
To: emc-pstc
Subject: Demonstrating compliance with Human Exposure to EMF
requirements



All

I'm attempting to demonstrate the compliance of our fixed wireless access
system with the human exposure to EMF requirements of Article 3.1a of the
RTTE directive:

The applicable standard, EN50385, requires the field strengths to be
measured/calculated according to EN50383 against the limits detailed in
1999/519/EC.

My reading of 1999/519/EC is that the maximum allow E-filed is 61 V/m for
2-300 GHz. 

I calculate that our subscriber equipment is generating a field of 10 V/m at
0.5m distance. 

So, so save measuring/calculating near field values, can I just add to the
user manual that you should not stand within 0.5m of the front of the
equipment? 
(The antenna wouldn't work so well if you did, and it would be difficult to
anyway as it typically pole/chimney mounted)

regards
Charlie Blackham
Approvals Manager
Airspan Communications


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RE: OK, what's going on?

[drcuthbert]

What would NARTE say about certified EMC engineers and technicians signing off
on equipment that does not make the grade? It would be great if everyone and
every company handled the issue of EMC ethically. But since the world does not
always work this way...I favor the idea of a fine for every unit that is
shipped from a lot that statistically fails. I.E. mandatory sampling (of boxed
and shipped units) and only a certain percentage are allowed to fail, etc.
Companies would then weigh the cost of compliance against the cost of
non-compliance. 
 
Devils advocate speaking now: But from the viewpoint of economics this would
of course add cost to every unit shipped. Is the additional manufacturing cost
to the public offset by any savings due to lower emissions and lower
susceptibility? Would society truly benefit from better EMC enforcement or
does this serve only the EMC community?  
 
Dave Cuthbert
Micron Technology
 
 

From: Mark Kirincic [mailto:mkirin...@houston.rr.com]
Sent: Thursday, March 27, 2003 8:53 PM
To: Stone, Richard A (Richard); lfresea...@aol.com; emc-p...@majordomo.ieee.org
Subject: Re: OK, what's going on?


To further clarify my point, all the major companies are guilty of this.  I
know of first hand information where a unit passed in Asia and failed here in
the states at the companies test lab, and they are forced by upper management
to ship the product anyway.  These companies are trying to get their product
out the door as cheaply as possible with little to no concern about the
consequences.  I have read in some of the responses that we should fine these
companies, that is a good point but that is only a slap on the wrist and a
chance most of them are willing to take.  
 
In my opinion, what really needs to be done is full accountability for failed
products that the company by having the company name made public at the FCC
and CE websites and trade journals.  Also have the companies pay for audits of
all the units that are in the country that fail to meet FCC and CE standards. 
What I am saying is to charge a flat fee per unit that fails.  Secondly, I 
would prevent them form selling into a market segment if the audit shows non
compliance of multiple units.  Have the company provide future proof of
compliance before shipping which will hurt them in their pocket book a lot
more than just a simple fine.
 
 
Mark J. Kirincic
mkirin...@houston.rr.com


- Original Message - 
From: Stone, Richard A  mailto:rsto...@lucent.com (Richard) 
To: 'Mark Kirincic' mailto:mkirin...@houston.rr.com  ; lfresea...@aol.com ;
emc-p...@majordomo.ieee.org 
Sent: Thursday, March 27, 2003 8:34 AM
Subject: RE: OK, what's going on?

Mark mentioned reports,
a paper trail...or is it?
 
Vendors doing the EMC/EMI ?,
who might a vendor be for say IBM or Dell?
would think the mfr'r would have an associate
there during testing like most of us do.
 
Seems it would be easy to look at the report,
from which test lab did it,
are they accredited?  if yes,
then there shouldnt be any questions..
only thing I see, maybe Disparity,
as readings can be differnet from lab to lab.
 
these days its ship now...or not at all..
and barely passing for PC's, since its class B
may be enough for the PC companies.
Richard,


From: Mark Kirincic [mailto:mkirin...@houston.rr.com]
Sent: Thursday, March 27, 2003 8:55 AM
To: lfresea...@aol.com; emc-p...@majordomo.ieee.org
Subject: Re: OK, what's going on?


I guess now its my turn to put in my two cents.  The major reason that you are
having a hard time finding units that pass is that all these major computer
companies rely on their vendors to test the products to FCC and CE limits. 
Since the majority of these companies have suppliers in the Taiwan and China
all of these units pass due to pressure from the major computer companies and
the vendors themselves.
 
These major computer companies then try to legitimize it by getting copies of
test reports showing the units are in compliance.
 
None of these companies will report each other to the authorities mainly
because they can not guarantee that all of their products pass and they fear
retaliation.  Their philosophy is as long as we have this report we can sell
this product until someone catches us and then they go into a major scramble
to fix the problem that was uncovered.
 
The only way to reduce this is through FCC and CE random audits.
 
I have worked for several major computer companies in my 19 years of
experience, and they all share this philosophy. One former company was the
exception, they were deathly afraid of bad press and they went to great
extremes to make sure their products passed with adequate margin.
 
I will get off my soap box now.  
Mark J. Kirincic
mkirin...@houston.rr.com


- Original Message - 
From: lfresea...@aol.com 
To: emc-p...@majordomo.ieee.org 
Sent: Tuesday, March 25, 2003 2:05 PM
Subject: OK, what's going on?

Hi all,

This e-mail has been prompted because of a number of things that 

RE: Calibrating police radar guns

[drcuthbert]

Is a semi-anechoic chamber really needed? Testing close-in inside of a
building should work, I would think.

   Dave Cuthbert
   Micron Technology


From: Hjálmar Árnason [mailto:hjal...@mi.is]
Sent: Thursday, March 27, 2003 4:14 PM
To: emc-p...@majordomo.ieee.org
Subject: Calibrating police radar guns



Hi Forum

I can recall back in November 2000 there was some discussions here in
this group on how to fight speeding tickets and many of you had good
advices.

I'm about to start on a project which includes calibrating and repairing
police radar guns.  This will probably involve setting up a semi-anechoic
chamber or OATS.  I have access to a room which can be used to set-up
a chamber and want to restrict the set-up to the radar freq. around 25 and
35 GHz.

I would appreciate if you could give some advice and direct me to the
right websites to get information.  I need both test equipment and material
for the chamber. The budget is low so second hand equipment is my goal.
Anyone selling his set-up ?.

Thank you kindly,

Hjalmar Arnason
Reykjavik
Iceland
hjal...@mi.is



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RE: high immunity

[drcuthbert]

Robert,
I figured 5 kV/m for a distance of 100 meters, over ground. Using commonly
available lab items (and a 100 kV power supply) I should be able to generate 5
kV/m at 3 meters during a 1 ns pulse width. Wonder what this would do to a
cell phone? 

  Dave Cuthbert
  Micron Technology


From: robert Macy [mailto:m...@california.com]
Sent: Wednesday, March 26, 2003 6:02 PM
To: drcuthbert; 'emc-p...@majordomo.ieee.org'
Subject: Re: high immunity


If GW, wouldn't that voltage be more like 600KV/m, or at
least 30KV/m?

 - Robert -

   Robert A. Macy, PEm...@california.com
   408 286 3985  fx 408 297 9121
   AJM International Electronics Consultants
   101 E San Fernando, Suite 402
   San Jose, CA  95112


On Wed, 26 Mar 2003 17:30:14 -0700
 drcuthbert drcuthb...@micron.com wrote:
 
 With the advent of E-weapons we might need some new
 immunity specs. I read that they can output several GW.
 Testing for equipment survival at over 5000 V/m should be
 fun (and profitable to some).
 
 Dave Cuthbert
 Micron Technology
 


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PC EMI

[drcuthbert]

Derrick,

I'm sure you used the antenna factors correctly but I'll put in my 2 cents
worth anyway. Were the AF's used correctly? You need the TX AF and the RX AF.
If the receive antenna factor was used as the transmit antenna factor that
will skew the calibration. 

  Dave Cuthbert


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high immunity

[drcuthbert]

With the advent of E-weapons we might need some new immunity specs. I read
that they can output several GW. Testing for equipment survival at over 5000
V/m should be fun (and profitable to some).

Dave Cuthbert
Micron Technology


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RE: OK, what's going on?

[drcuthbert]

Derek,
 
most interesting data. I have two questions: What software are you exercising
the PC's with and is the spread spectrum enabled? I assume you are using an
RBW of 120 kHz and using Quasi-peak detection.
 
In my limited experience I have found that the software that is exercising the
PC can make quite a difference. It is my understanding that many PC's are
tested with H's printing to the screen. When running a game such as Doom the
emissions will go up several dB. And if the spread spectrum is not enabled
there will be an increase of 8 dB or so. I'm curious as to what the failing
frequencies are. 
 
   Dave Cuthbert
   Micron Technology

From: Stone, Richard A (Richard) [mailto:rsto...@lucent.com]
Sent: Tuesday, March 25, 2003 1:30 PM
To: 'lfresea...@aol.com'; emc-p...@majordomo.ieee.org
Subject: RE: OK, what's going on?


Derek,
doesnt say whether you took the 
uncompliant equipment straight from your
lab to another without making any changes...
be interesting to see what the data is,
since PC's are listed to class B...
you may have something..
 
but its always good to get a second
result from lab B.
 
Richard,


From: lfresea...@aol.com [mailto:lfresea...@aol.com]
Sent: Tuesday, March 25, 2003 3:05 PM
To: emc-p...@majordomo.ieee.org
Subject: OK, what's going on?


Hi all,

This e-mail has been prompted because of a number of things that have all come
together. This may take a little reading, but please stick with it.

Last note... this is not intended to pick on any individuals, or organization,
but I do want to stir the pot.

I operate an engineering lab, helping clients harden their designs to meet EMC
requirements. In this particular instance, I was working for a small client,
on a card  that goes in the PC . In order to test I need a host PC. So, to
save money, the card maker supplies 2 clones.

Neither of the two PCs passed emissions testing with the card, in fact, above
100 MHz, they fail even the Class A limit: badly! So, before calling my
client, I pull his card, the PC is no different, I pull the monitor, then the
keyboard, then the mouse... No different.  I test just the PC chassis one at a
time. On their own, booted and then the peripherals removed. Not even close to
passing.

Disgruntled, I get my office PC... Fail. I get my kids PC.. over 20 dB over
the limit!

So, I think so much for clones... I buy 2 Dell ( sorry, no point trying to
hide names... ) desktops, both fail, quite badly. However, they have very
similar noise profiles...

Can 5 PC's all fail? I think my measuring system is set -up wrong. So I verify
this. I am within 1 dB of what I expect when I inject a signal from a signal
generator and account for antenna factors.

Here lies the question: why can I not find a PC that passes? Worse, since they
don't pass, who is chasing them down to enforce the requirements? I'm unhappy,
because I am taking a clients money to make him meet the requirements, when it
seems no one else is.

Now, what's making this worse for me, is that I am an EMC Lab assessor. So, I
go to labs and make them jump through hoops so that they produce, as
consistently as possible, data the characterizes a product. Exercises, like
those performed by USCEL, show that labs can have very consistent results.
Anyone that stands up and says EMC is not a field where consistency can be
achieved, should not be in the compliance business: please close your lab. So
if the test are consistent, why the HUGE variations?

In the 20+ labs I have assessed, I feel that almost every one had an ethical
approach. Ironically, I felt that the bigger companies I visited like HP and
Intel were exceptional: both ethically and technically. The rest of the labs
were between good to very good. So cheating is unlikely..

I have now spent about 60 man-hours looking for a PC that passes FCC Class B
emissions. Something that I should just be able to go to the store and get. As
yet, I have no PC. Our field, it appears, is not a level playing field. It
appears more like a rugby game in which we have no referee!

So why are there no fines being levied? Especially since it seems I can find
non-compliant products everywhere! Is the self policing approach out of
control?

I intend to take this up with the FCC. Is there anyone out there that is
supportive of this action ( which means you must be doing things right.. )? Am
I wasting my time ( in which case if this is all lip service... why should we
even test )? Or am I missing something ( I listen to 2 by 4's )?

Derek Walton
Owner of an EMC Lab
EMC Lab Assessor
NARTE EMC Engineer
30 years of EMC experience 

NEC-2 simulations

[drcuthbert]

I have been using NEC-2 antenna software for simulations of EMC situations.
Antenna-to-antenna, ferrites on cables, DUT cables, BC station field strength,
and such. Anyone else using NEC for this?

 Dave Cuthbert
 Micron Technology


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RE: surge Z?

[drcuthbert]

Thanks to everyone for the numbers. To clarify, the device is a DC/DC
converter. We will be applying the surge to the DC input and to the DC output.
I have ordered EN 61000-4-5 to get the details.

   Dave


From: John Barnes [mailto:jrbar...@iglou.com]
Sent: Thursday, March 20, 2003 9:45 AM
To: drcuthbert; emc-p...@majordomo.ieee.org
Subject: Re: surge Z?


Dave,
Section 6.1 of EN 61000-4-5:1995 says the generator has an effective
output impedance of 2 ohms.

John Barnes KS4GL, PE, NCE, ESDC Eng., SM IEEE
dBi Corporation
http://www.dbicorporation.com/


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surge Z?

[drcuthbert]

Anyone know the source impedance used for EN 61000-4-5 Surge testing? 

Dave Cuthbert
Micron Technology


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RE: antenna port conducted emissions

[drcuthbert]

Aaron,

I believe you use the standard receiver RBW and use the peak hold mode.
Depending on how the spread spectrum operates (I.E. wideband noise, or
frequency hopping, etc.) the receiver and the transmitter will eventually line
up.

   Dave Cuthbert


From: Price, Ed [mailto:ed.pr...@cubic.com]
Sent: Wednesday, March 19, 2003 11:10 AM
To: 'Low, Aaron S'; emc-p...@majordomo.ieee.org
Subject: RE: antenna port conducted emissions




-Original Message-
From: Low, Aaron S [mailto:aaron.s@lmco.com]
Sent: Wednesday, March 19, 2003 7:44 AM
To: emc-p...@majordomo.ieee.org
Subject: antenna port conducted emissions



Folks,

I am interested in your opinions regarding antenna port 
conducted emissions
(MIL-STD-461D CE106) on a spread spectrum/frequency hopping device.

Is it practical to automatically measure (using a swept scan 
EMI receiver)
emissions from such a device?  I would think that when using 
spread spectrum
and a swept scan receiver, the receiver has some large probability of
missing the emissions caused by a particular harmonic when using swept
scanning systems.

The limit for CE106 (transmitters) is derived from the power of the
fundamental (there is no fundamental, only a band of 
operation), how do you
measure that power on the EMI receiver?

Does anyone have any experience/advice they would be willing 
to part with?

Thanks
Aaron Low

ps.  I am relatively new to this field, so my question may 
seem very basic
to many of you; please excuse me.




Aaron:

First question is are you sure you should be working to 461D? 461E came out
20 August 1999.

Now, to address your technical situation. Yes, you do have a fundamental.
Just because it's hopping doesn't mean it's not there. Granted, 461 CE06
(later CE106) originated in the era of non-hopping systems, and may address
them better in a future revision, but it does say that your reference will
be the peak power level of the fundamental.

You can measure the peak power by using a spectrum analyzer in peak hold,
using sufficient bandwidth to ensure the detector actually charges to the
peak during the time that the fundament dwells in the SA resolution
bandwidth. Sometimes you can sweep a small portion of spectrum, or you can
go to zero span width and just sit at some frequency waiting for the
fundamental to hop there.

You may find that the fundamental amplitude varies across the hopping range,
so you might need to disable the hopping and fix the fundamental to one or
more specific frequencies. Remember when looking for harmonic content, the
hop sizes will be n x the fundamental hop size.

Probabability of intercept is a problem, and I usually scan very slowly and
do several overlaid sweeps of the spectrum. Many of the transmitters that I
see have a short duty cycle (like 7 uS on and 993 uS in standby), so this
makes the signal acquisition even more challenging. Sometimes I set
automated scans to run 16 hours overnight, or over a weekend.


Regards,

Ed


Ed Price
ed.pr...@cubic.com
Electromagnetic Compatibility Lab
Cubic Defense Systems
San Diego, CA  USA
858-505-2780  (Voice)
858-505-1583  (Fax)
Military  Avionics EMC Is Our Specialty
Shake-Bake-Shock - Metrology - Reliability Analysis


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RE: CE mark on development/evaluation boards ?

[drcuthbert]

We are currently going through a similar process with a board designed for
in-house use. We are planning to go for CE certification. We designed it to
EN61010 and it passed our own safety testing and radiated/immunity and ESD.
But it seems to be a gray area as to having it certified or not. I don't want
to self-certify and so a competent body looks like the way to go. 

   Dave Cuthbert
   Micron Technology


From: John Woodgate [mailto:j...@jmwa.demon.co.uk]
Sent: Friday, March 07, 2003 2:24 PM
To: emc-p...@majordomo.ieee.org
Subject: Re: CE mark on development/evaluation boards ?



I read in !emc-pstc that Peter L. Tarver peter.tar...@sanmina-sci.com
wrote (in nebbkemlgllmjofmoplememaeeaa.peter.tar...@sanmina-sci.com)
about 'CE mark on development/evaluation boards ?' on Fri, 7 Mar 2003:

I also have a current need for this information and would
appreciate being copied on anything off the list.

Why off-list? It seems to me that a lot of people would be interested in
answers, especially if one came from one of the suppliers mentioned.

[sigsnip]

 -Original Message-
 From: owner-emc-p...@majordomo.ieee.org
 [mailto:owner-emc-p...@majordomo.ieee.org]On
 Behalf Of Anthony Moulds
 Sent: Friday, March 07, 2003 9:30 AM
 To: emc-p...@majordomo.ieee.org
 Subject: CE mark on development/evaluation boards ?

I didn't get this message, so apologies to PT for hi-jacking his
response.


 Hi,

 It's unclear (to me anyway!) if
 development/evaluation test board products
 should be tested for
 compliance with the EU EMC directive. I often see
 boards supplied without
 the CE mark,
 e.g. Xilinx, TI, Altera development boards. Are
 these type of products
 exempt from the
 European directive ?

Well, are they shipped as functioning units? If you just get a pile of
parts, and the supplier has no *detailed* idea how you are going to
build them up, nor what software and peripherals you will add, the
supplier CAN'T carry out any meaningful EMC tests, let alone safety, so
the only **sensible** solution is to regard them as outside the scopes
of the Directives.

However, having 'sensible' and 'Directives' in the same sentence is
something of an oxymoron, so if anyone who has a definitive answer would
post, it would be very helpful.
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
Interested in professional sound reinforcement and distribution? Then go to 
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!


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RE: RADIATED IMMUNITY - Some Actual Measurements of FS

[drcuthbert]

Why not blast the DUT with 10V/m at all frequencies? If it misbehaves in the
3V/m bands then 3V/m could be tried. If you want some high E-field try my
house (or another ham's house). I often run fields to the FCC safety limit in
my house. When operating 160 meters I can light a 40 watt fluorescent tube by
holding it in my hand at the operating position. I believe the peak limit at
1.8 MHz is 500 V/m. The equipment in my house is not affected (well just a
little) with the application of a few ferrites and filters. The field in the
adjacent neighbors homes is in the tens of volts/m. No complaints yet. Just
remember, in words of N6SU if you can't see it it can't hurt you.

Dave Cuthbert WX7G
Micron Technology


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EDN article

[drcuthbert]

Here is a link to my latest EDN Design Idea article (Transmission line tests
1-kW device using only 100W): http://ww
.e-insite.net/ednmag/index.asp?layout=a
ticlestt=000articleid=CA276211pubdate=2%2F20%2F2003spacedesc=designideas

 Dave Cuthbert
 Micron Technology


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RE: Shieled ethernet cables in Germany

[drcuthbert]

The fact that going from unshielded to shielded cable cut emissions by 6 dB
does not necessarily mean that the shield cut cable emissions by only 6 dB. It
could mean that the cable emissions have been greatly reduced but another part
of the system has emissions that are 6 dB below the original configuration.
Like pealing an onion and revealing the layers of EMI.

   Dave Cuthbert
   Micron Technology


From: Ken Javor [mailto:ken.ja...@emccompliance.com]
Sent: Monday, February 24, 2003 7:22 AM
To: Jan Vercammen; emc-p...@majordomo.ieee.org
Subject: Re: Shieled ethernet cables in Germany



To Jan Vercammen and Michael Nagel and the whole forum,

If a decent shield only provides 6 dB of shielding effectiveness at best,
that is an indictment of the termination impedance(s) and Doug Smith is
right, other techniques need to be investigated for reducing emissions and
immunity.

Ken Javor




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RE: IEC 61010 requirements

[drcuthbert]

Maybe he had a special low EMI cell phone? But seriously, a useful product
would be a cell phone detector with an audible alarm, or a silent alarm to
alert security. 

Dave Cuthbert 

From: John Woodgate [mailto:j...@jmwa.demon.co.uk]
Sent: Saturday, February 22, 2003 1:05 AM
To: emc-p...@majordomo.ieee.org
Subject: Re: IEC 61010 requirements



I read in !emc-pstc that peter merguerian pmerguerian2...@yahoo.com
wrote (in 20030221231714.74613.qm...@web14806.mail.yahoo.com) about
'IEC 61010 requirements' on Fri, 21 Feb 2003:
The other day, I called a surgeon and he happened to be in the 
operating room with his cellphone performing an operation. Does 
that make his cellular comply with IEC 601-1?

Maybe not, but there are VERY serious EMC issues. No cell-phone should
be switched on in an OR.
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
Interested in professional sound reinforcement and distribution? Then go to 
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!


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RE: RE02 cabling problem

[drcuthbert]

I completely agree with Ken Javor. Solid theory and solid conclusions.

   Dave Cuthbert


From: Ken Javor [mailto:ken.ja...@emccompliance.com]
Sent: Thursday, February 20, 2003 4:53 PM
To: pwell...@csw.l-3com.com; 72146@compuserve.com; emc-p...@ieee.org
Subject: Re: RE02 cabling problem



There is another implied concept of questionable validity in this latest
posting.  The way I read it, Mr. Wellington is talking about filtering
signals emanating from the support equipment as it passes through a bulkhead
between control and test chambers.  Such signals usually require no
filtering whatsoever, because if they have any bandwidth at all, they are
run with dedicated returns (such as a twisted pair or a twisted shielded
pair) and have no radiation efficiency to speak of. What requires filtering,
and what is ameliorated by proper PCB layout, as he alluded to in an earlier
post, is common mode emissions.  These can be filtered to a very high degree
with no impact on intentional signals.  Common fixes are snap on ferrite
beads and line-to-ground caps.  Clearly the line-to-ground caps should not
attenuate the desired signal, but in most if not all cases the undesired cm
current is orders of magnitude higher in frequency than the intentional
signal.  In those cases where this is not the case, the military would run
intentionally high frequency signals within shielded cables (think
MIL-STD-1553 and fibre channel) which, if properly terminated, will provide
all the protection necessary without resort to either filtering or
over-braids.  Specifically, if the support equipment or its environment
resulted in high frequency cm currents conducted on the outside of a
shielded cable, that cable should be terminated peripherally to a connector
at the bulkhead as it passes into the test chamber.  If the cable is not
shielded and the source is the ambient, then shielding of the cable external
to the test chamber is both proper and necessary, and has no effect on the
validity of the test set-up within the chamber.  Further, it requires no
input from the customer, because it does not affect the delivered product
configuration.  If the test support equipment itself is the cm source, then
any cm filtering necessary to attenuate those emissions before they enter
the test chamber is again proper and necessary, external to the test
chamber.  It might be said that such filtering could reduce cm currents
emanating from the test sample, but this is not a big problem for a couple
of reasons.  First it is easy to determine whether it is support equipment
or the test sample which is driving the currents, by sequentially
de-energizing suspected sources and noting the effect on the emissions.
Secondly, the standard effectively requires at least 3 meters of cabling
between test sample and bulkhead.  Above 10 MHz the cable is electrically
long and the effect of a filter at the bulkhead does not directly impact the
level of cm current on the cable, but only indirectly as its impedance is
transformed by the electrical length and distributed characteristic
impedance of the cable in question.  If the mil-std EMI test set-up were so
well-controlled that every test chamber and every test bench were of
precisely equal size and configuration and no matter where the test was
conducted the entire test set-up including cable layout were identical
within inches, then it might be productive to worry about changing a common
mode impedance at the end of a three meter cable.  In my experience, such is
hardly the case.




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RE: Japan 13.56 MHz

[drcuthbert]

Richard,
is the proposed increase to support magnetic field signaling, such as in
automobiles?

   Dave Cuthbert


From: richwo...@tycoint.com [mailto:richwo...@tycoint.com]
Sent: Friday, February 21, 2003 6:30 AM
To: emc-p...@majordomo.ieee.org
Subject: Japan  13.56 MHz



Last year a Japan was considering raising the intentional emissions limit at
13.56 MHz for short range devices to match the ETSI/FCC limit of 42 dBuA/m.
Does any one know if this proposal was adopted? 

Richard Woods
Sensormatic Electronics
Tyco International



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RE: About Radiated Measurements

[drcuthbert]

Muriel,

interesting question. Considering common mode noise on the load wires: With
the load at the end of the wires, but not grounded, you have a monopole
antenna. With the load wires terminated into a filter (I'm assuming low-Z to
GND) you have a loop antenna. I ran a quick simulation using NEC-2 at 100 MHz
using a wire length of 13 cm for an inverted-L configuration (3 cm vertically
and 10 cm horizontally). The loop has dimensions are; 3 cm vertically, 10 cm
horizontal, and 3 cm back to GND. Given 1 mV and a 10 ohm source impedance the
loop radiates 19 pW. Given the 1 mV source the monopole radiates 47 fW. A 26
dB difference given these parameters. Placing the power supply outside through
filters is the winner for the most radiation, given these randomly selected
parameters.

Are you orienting the power supply on each of the three axis? And rotating it
at each? This is what I have found inconvenient about TEM cells. 

Dave Cuthbert
Micron Technology


From: Muriel Bittencourt de Liz [mailto:mur...@eel.ufsc.br]
Sent: Thursday, February 20, 2003 11:52 AM
To: EMC-PSTC List
Subject: About Radiated Measurements



Group,

I have a doubt concerning radiated emissions measurement:

- For radiated emissions measurement of switched mode power supplies using a
TEM cell, should I leave the loads of the supply inside or outside the
cell?? My TEM cell have filtered connections for DC loads.

Thanks in advance for your help.

Best Regards,

Muriel





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RE: Custom Units in EU

[drcuthbert]

I should emphasize that this applies to equipment build by company A for use
by company A only. A label on the equipment stating this is probably a good
idea.

   Dave Cuthbert


From: drcuthbert [mailto:drcuthb...@micron.com]
Sent: Wednesday, February 19, 2003 3:28 PM
To: 'Joe P Martin'; emc-p...@majordomo.ieee.org
Subject: RE: Custom Units in EU



Joe,
I looked into this last year. It appears to me that one can import
non-certified 61010-type equipment for in-house use. But, it technically must
still be able to pass safety, EMC, ESD, surge, and so on. Pretty much like
self certification without the final step or two.

Dave Cuthbert
Micron Technology 


From: Joe P Martin [mailto:marti...@appliedbiosystems.com]
Sent: Wednesday, February 19, 2003 1:49 PM
To: emc-p...@majordomo.ieee.org
Subject: Custom Units in EU



Greetings,

We are planning to manufacture up to 50 units for laboratory use.  Each of
these units will be one of a kind.  These units will be shipped to the EU
to our own laboratory and operated by our personnel.  If I recall correctly
there are exemptions for one of a kind units for EMC, LVD and Machinery
Directives.  However, I was unable to locate this information in the
guidelines to these Directives.  Can members of the group provide me with
specific information regarding the requirements, if any, for one of a kind
units located in the manufacturers facility and operated by employees of
the manufacturer in the EU?

All responses are appreciated.

Regards

Joe Martin
Applied Biosystems
marti...@appliedbiosystems.com



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RE: Measuring Power Supply Output Current

[drcuthbert]

Rick,
I like to use a clamp-on DC current probe and an oscilloscope. Tektronix
makes these probes. If the 'scope has an RMS feature it will calculate the
RMS current over the length of the trace. In this way you can adjust the
length of the RMS operation. If your 'scope does not have this feature you
can do an RMS calculation on paper. It is the square root of the mean of the
squares. I divide the trace into 10 segments and it is quite accurate. If
you don't have a clamp-on DC probe you can do it with a shunt resistor. You
will want something lower than 5 milliohms to keep the burden voltage low.
Fluke makes a nice 1 milliohm shunt or you can buy a resistor and do it. You
will have to cut the wires. How to connect the 'scope to a floating current
shunt? You can translate the signal to ground using an op amp and a FET (not
a diff amp circuit). But there is a much simpler method that is sure to
upset product safety guys. Cut the ground prong off of the 'scope AC power
(use a battery operated 'scope). The 'scope chassis is now DC referenced to
one end of the shunt resistor and you can make your measurement across the
shunt. I have done this, with an isolation xfmr, to 1 kV. After a couple of
good shocks I was trained not to touch the 'scope chassis and earth ground.

   Dave Cuthbert
   Micron Technology


From: rbus...@es.com [mailto:rbus...@es.com]
Sent: Monday, February 17, 2003 1:19 PM
To: emc-p...@majordomo.ieee.org
Subject: Measuring Power Supply Output Current



I have been asked by my TUV office to measure the actual output current
for each of the 5-7 voltages on my PC power supplies. The purpose of
this is to baseline the maximum output current in terms of maximum
power, not instantaneous current, for each of the various motherboards
we use.

On the surface it seemed like a simple exercise of putting a DC current
meter in series with each of the outputs. Given that the current demand
for each of these outputs is dynamic, corresponding with the processing
activity, does it make sense to measure this output current with a True
RMS meter? 

If this is the case, I would assume that the True RMS meter takes the
measurement based on some type of a time weighted average or sample
time. Do any of you have a feel for how this is calculated?

How do manufacturers of these PC supplies address the maximum output
current ratings for each voltage. Does this rating take into account
PEAK demands for current (or over current)?

Thanks

Rick Busche
Evans  Sutherland
rbus...@es.com



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RE: Real product interference source at 121 MHz

[drcuthbert]

Kurt,
this could be aviation communications. AM voice is centered at about 121
MHz. 

   Dave


From: Kurt Fischer [mailto:kurt.fisc...@hyperinterop.com]
Sent: Tuesday, February 11, 2003 8:03 AM
To: emc-p...@majordomo.ieee.org
Subject: Real product interference source at 121 MHz


Hello all,
 
A strange request but this has become an interference issue with a sattelite
communications link There seems to be a very strong interferer at 121 MHz
that is intermittent in nature and physically located in Northern
USA/Canada. 
 
It could be the marketing of a non-compliant consumer products or perhaps
some after market sattelite rec. retro-fit kit??
 
Has anyone else had this experience in the last year --- (the problem was
not present 2 years ago)?
It does appear to getting worse and is spreading geographically as well.
 
Regards,
Kurt Fischer
Hyper Corp
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^y\v+:ybb2+hnȭya0{by種̡ޙ?\:jw*.˛
بǧvfj:+v   瞢0m   ^)޺{.n+l5h.ǧvf-b2)²ڶF-צr-rz(
+u֯z֭ah%̪-ʉ̱ݙbrtۭzxy+!zi^'z!
ⱷ   p{ॕǢ{^+bwWr-r,)౪j7!jwly*zma60rx(l


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RE: best screw/washer choices for attaching PCB to Chassis?

[drcuthbert]

Kim,

Screw/Washer choice:
- should a washer be used or not? ONE COMPANY I WORKED FOR USED SCREWS WITH
INTEGRAL STAR WASHERS. WE NEVER HAD ONE WORK LOOSE EVEN IN MOBILE
APPLICATIONS.

- Is an adhesive like Loctite a reasonable alternative to lock washers in
this case? I WOULD THINK LOCKTITE WOULD BE GOOD BUT I WOULD DESIGN IT TO
MAKE SURE THE SCREW IS NOT REQUIRED AS A FAULT CURRENT PATH.

- should the screw be zinc plated? or some other plating? I FAVOR USING THE
SAME PLATING THAT THE PEM NUT USES.

PCB layout:
- Should we use a plated through-hole with ground planes connected inside
the hole? WE USED PLATED THRU BUT THE CONNECTION TO THE NTERNAL LAYERS CAN
FAIL SO I WOULD NOT RELY ON THEM.

- or a non-plated hole with vias in the surface layer pad connecting to the
ground plane? YES VIAS, OUTSIDE THE SCREW HEAD AREA ARE PREFERRED. THE PAD
SHOULD BE ON THE PEM NUT SIDE SO THAT THE SCREW IS NOT A PART OF THE FAULT
CURRENT PATH.

I WOULD DEVELOP A TORQUE SPEC, USE A TORQUE WRENCH, AND PUT THIS IN THE
ASSEMBLY DOCUMENTATION.

  Dave Cuthbert
  Micron Technology


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EMC-Related Functional Safety

[drcuthbert]

An interesting article in the January issue of EMC Compliance Journal
EMC-Related Functional Safety
http://www.compliance-club.com/article.php?sid=119mode=order=0
   
Dave Cuthbert


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RE: GPIB filtered bulkhead connectors.

[drcuthbert]

Simply terminating the shield at the screened room wall eliminates common
mode shield current. No more filtering needs to be done.

   Dave Cuthbert
   Micron Technology


From: Luke Turnbull [mailto:luke.turnb...@trw.com]
Sent: Monday, February 10, 2003 7:38 AM
To: 
Subject: GPIB filtered bulkhead connectors.



Group,

Does anyone know where I can buy filtered bulkhead connectors for running
GPIB cables through screened room walls.  Approximate cost?

Alternatively, does anyone know suppliers and cost for GPIB fibre-optic
extenders.

Thanks,

Luke Turnbull



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RE: Power Supply Vendor Reference

[drcuthbert]

Ed,
I use Vicor for power in this range. We have had good reliability in a lab
setting. The documentation could be better but we are used to Vicor and just
keep using them.

   Dave Cuthbert


From: Price, Ed [mailto:ed.pr...@cubic.com]
Sent: Tuesday, February 04, 2003 4:10 PM
To: 'EMC-PSTC List'
Subject: Power Supply Vendor Reference



Group:


I had a project engineer ask me if I could suggest any vendors for a modular
power supply for his project. I say project, because it's a ground-portable
box that does something or other which he didn't think I needed to know
about.

All I know is that he expects to put about 1kW of 208V, 50/60 Hz, Delta
power into the power supply, and get 270 VDC, 48 VDC, 28 VDC, +/- 15 VDC and
8 VDC out of it.

Anyone care to recommend their favorite PS vendor (or themselves)?


Thanks,

Ed 

Ed Price
ed.pr...@cubic.com
Electromagnetic Compatibility Lab
Cubic Defense Systems
San Diego, CA  USA
858-505-2780  (Voice)
858-505-1583  (Fax)
Military  Avionics EMC Is Our Specialty
Shake-Bake-Shock - Metrology - Reliability Analysis



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RE: EN60950 protective conductor test (was Re: Circuit Breaker Tr ipping Dring Fault Tests)

[drcuthbert]

I recently designed a piece of in-house gear that uses the PCB as part of
the protective earth GND return. At first I thought I would be forced to use
a wire(s) only (which was awkward given the mechanics of the unit) but then
was convinced that EN61010 did not require it. To get around the via issue
we kept the path on one PCB layer. We designed for well over 20 amps
continuous. The bare metal rear panel is connected to the power connector
GND with the standard YELLOW/GREEN wire. The cabinet and front panel are
connected through the PCB with either metal spacers or a metal bracket. When
testing this do I return the current through the rear panel only, or do two
more tests using the cabinet and the front panel? The cabinet and the front
panel do not have dedicated GND connections or any unpainted metal.

   Dave Cuthbert
   Micron Technology



From: Chris Maxwell [mailto:chris.maxw...@nettest.com]
Sent: Tuesday, February 04, 2003 11:25 AM
To: Lou Aiken; Peter L. Tarver; emc-p...@majordomo.ieee.org
Subject: RE: EN60950 protective conductor test (was Re: Circuit Breaker
Tripping Dring Fault Tests)



PC traces are easier to assemble and the assembly can be done in a tighter
space.  I think (just an opinion)  that proper design could make this type
of system more reliable as well with less chances of wires coming loose...

 -Original Message-
 From: Lou Aiken [SMTP:ai...@gulftel.com]
 Sent: Tuesday, February 04, 2003 11:36 AM
 To:   Peter L. Tarver; emc-p...@majordomo.ieee.org
 Subject:  Re: EN60950 protective conductor test (was Re: Circuit
Breaker Tripping Dring Fault Tests)
 
 
 Why not provide a fuse to prevent deterioration of the PE trace on a PCB?
 
 Joking of course, but now that I have your attention, I would like to see
 this thread move away from the physics and discuss what practical reasons
 there are for using PC traces to provide earth fault circuits.
 
 
 Lou Aiken, LaMer LLC
 27109 Palmetto Drive
 Orange Beach, AL
 36561 USA
 
 tel ++ 1 251 981 6786
 fax ++ 1 251 981 3054
 Cell ++ 1 251 979 4648
 - Original Message -
 From: Peter L. Tarver peter.tar...@sanmina-sci.com
 To: emc-p...@majordomo.ieee.org
 Sent: Tuesday, February 04, 2003 9:53 AM
 Subject: RE: EN60950 protective conductor test (was Re: Circuit Breaker
 Tripping Dring Fault Tests)
 
 
 
 Not quite.  I^2·t will tell you the let through current of
 the copper trace, but will not necessarily tell you if the
 construction will be compliant.  The compliance criteria for
 this test include:
 
 * no damage to the trace (no lifting, probably no
 discoloration)
 * no damage to the PWB (no delamination, burning; I don't
 know if this includes burning off of solder mask)
 * before and after earthing impedance must comply with the
 0.1 Ohm maximum impedance
 * no change in earthing impedance greater than 10% of the
 before and after earthing impedance results
 
 There is also the much more variable solder in the earthing
 path.  While manufacturing techniques have come a long way
 in terms of consistency, the amount of solder in a joint and
 the quality of the joint itself can play a significant role.
 It should be expected that a lower melting point solder will
 perform less well than a higher melting point solder.
 Appropriate process controls will have a positive effect.
 
 These are some of the reasons some form of safety agency
 factory auditing of this type of construction is normal.
 
 
 Regards,
 
 Peter L. Tarver, PE
 Product Safety Manager
 Sanmina-SCI Homologation Services
 San Jose, CA
 peter.tar...@sanmina-sci.com
 
 
  -Original Message-
  From: Chris Maxwell
  Sent: Tuesday, February 04, 2003 5:32 AM
 
 
  Exactly!
 
  Chris Maxwell
 
 
   -Original Message-
   From: drcuthbert [SMTP:drcuthb...@micron.com]
   Sent: Monday, February 03, 2003 7:50 PM
  
   What is needed is the I squared t rating of the
  breaker. Then the (I^2)(t)
   rating of the PCB. Then you know if the PCB can
  take it.
  
  Dave Cuthbert
 
 
 ---
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RE: EN60950 protective conductor test (was Re: Circuit Breaker Tr ipping Dring Fault Tests)

[drcuthbert]

Chris,
I have estimated this type of thing in the past assuming adiabatic
conditions. That is, the energy put into the material heats it and no energy
is lost during the heating. This gives the worse-case temperature rise. So,
what is needed is the electrical resistance of the material and the specific
heat of the material. Let's look at the case of a trace sized to handle 25
amps continuously with a 40 degree C rise.
http://www.geocities.com/CapeCanaveral/Lab/9643/TraceWidth.htm

We will pulse it with 200 amps for 20 ms and see what the heat rise is
assuming adiabatic conditions:

The trace is 500 mils (1.27 cm) wide, 1 inch (2.54 cm) long, and is 1 oz
copper (1.4 mils or 3.55 x10^-3 cm). The resistance is 1 milliohm. The
energy absorbed is (I^2)(R)(t) = 0.8 joules. The density of copper is 8.96
gr/cm^3. The mass of this trace is 0.103 gr. The specific heat of copper is
0.386 J/gr*C. The specific heat of this trace is therefore 0.0398J/C which
gives a heat rise of 20 degrees C for a 200 amp, 20ms pulse.  I have
neglected the change in resistance and specific heat with temp.

I have actually viewed the voltage drop across a metal line as it was heated
by a pulse. From this one can plot the temperature versus time. The real
issue, I think are the vias and vias with heat reliefs. How many do we use?
We can calculate the vias the same way and come up with a recommendation. Of
course, it would be great to check this with experiments. I would be
interested in doing this if someone here wants to partner on the project. I
can have a test board designed and built and do the pulsing. What I need are
standards, suggestions, circuit breaker data, and any other help (such as
researching to see if we are reinventing the wheel. The results would then
be published in Compliance, Conformity, or Printed Circuit design magazine.


 Dave Cuthbert
 Micron Technology


From: Chris Maxwell [mailto:chris.maxw...@nettest.com]
Sent: Tuesday, February 04, 2003 6:32 AM
To: drcuthbert; John Woodgate; emc-p...@majordomo.ieee.org
Subject: RE: EN60950 protective conductor test (was Re: Circuit Breaker
Tripping Dring Fault Tests)


Exactly!  There is lots of data and tables available on the web for steady
state current; but I haven't found any sources that would give the (I^2)(t)
values for wires or PCB traces.   Such tables would take a great deal of
mystery out of this subject.  Right now, the best guess is to go by steady
state current rating; but there must be faults in this.  A PCB trace that
can handle 10 Amps of steady state current has a totally different geometry
than a wire that can handle 10 Amps of steady state current.  This would
make heat dissipation different; and I would assume that it would make the
fusing characteristics (I^2)(t) slightly different as well.

Chris Maxwell | Design Engineer - Optical Division
email chris.maxw...@nettest.com | dir +1 315 266 5128 | fax +1 315 797 8024

NetTest | 6 Rhoads Drive, Utica, NY 13502 | USA
web www.nettest.com | tel +1 315 797 4449 | 




 -Original Message-
 From: drcuthbert [SMTP:drcuthb...@micron.com]
 Sent: Monday, February 03, 2003 7:50 PM
 To:   'John Woodgate'; emc-p...@majordomo.ieee.org
 Subject:  RE: EN60950 protective conductor test (was Re: Circuit
Breaker Tripping Dring Fault Tests)
 
 
 What is needed is the I squared t rating of the breaker. Then the (I^2)(t)
 rating of the PCB. Then you know if the PCB can take it. 
 
Dave Cuthbert
 
 


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RE: EN60950 protective conductor test (was Re: Circuit Breaker Tr ipping Dring Fault Tests)

[drcuthbert]

What is needed is the I squared t rating of the breaker. Then the (I^2)(t)
rating of the PCB. Then you know if the PCB can take it. 

   Dave Cuthbert


From: John Woodgate [mailto:j...@jmwa.demon.co.uk]
Sent: Monday, February 03, 2003 4:15 PM
To: emc-p...@majordomo.ieee.org
Subject: EN60950 protective conductor test (was Re: Circuit Breaker
Tripping Dring Fault Tests)



I read in !emc-pstc that cnew...@xycom.com wrote (in 85256CC2.005F2DA4.
0...@notes.fw.xycom.com) about 'EN60950 protective conductor test (was
Re: Circuit Breaker  Tripping Dring Fault Tests)' on Mon, 3 Feb
2003:

My UL guy tells me that I should expect the typical service type CB to be
rated
up to  + 10%.  So it appears that  I need to concern myself with a burst of
current
up to approximately 22 amps for the 20 amp AC circuit that my product is
being
evaluated for.

Until it trips, your CB lets through the **whole 200 A**. The trip
current is practically irrelevant in this test; what matters is the trip
TIME. The board trace may stand 200 A for 50 ms but not for 100 ms.
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk

Interested in professional sound reinforcement and distribution? Then go to 
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!


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RE: BeCu problem

[drcuthbert]

I worked on a 1 MW, 160 GHz Gyrotron in 1982 that used a diamond waveguide
window. Yes diamond is the up-and-coming power electronics material with 50X
the thermal conductivity of copper. It is also starting to be used as a
protective thinfilm material.

  Dave Cuthbert


From: Fred Townsend [mailto:f...@poasana.com]
Sent: Friday, January 31, 2003 3:03 PM
To: John Woodgate
Cc: emc-p...@majordomo.ieee.org
Subject: Re: BeCu problem



John, tubes are like vacuum deposition chambers. I have difficulty believing
that
a fancy form of carbon would be of any use in molded structures, HV, or
HVAC.
These conditions are all found  in radar tubes.

Also, thanks to Greggs comment about fancy screw drivers, I remembered that
BeCu
screw drivers, wrenches, etc. are used by the military in explosive
environments
because of their no sparking characteristics.

Fred Townsend

John Woodgate wrote:

 I read in !emc-pstc that Fred Townsend f...@poasana.com wrote (in
 3e3a35fb.6ecc...@poasana.com) about 'BeCu problem' on Fri, 31 Jan
 2003:
 BeO has seven times better thermal conductivity than AlO (alumina).
There is
 no real substitute for BeO at high power levels.  It is still used by the
 Military in high power radar applications such as tubes.

 Vapour Phase Deposition of diamond may replace BeO, with improved
 thermal properties, AIUI, and no toxicity problem.
 --
 Regards, John Woodgate, OOO - Own Opinions Only.
http://www.jmwa.demon.co.uk
 Interested in professional sound reinforcement and distribution? Then go
to
 http://www.isce.org.uk
 PLEASE do NOT copy news posts to me by E-MAIL!

 ---
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RE: EN55022:1998 + A1:2000

[drcuthbert]

The MFJ-259B is available from MFJ Enterprises, a ham radio accessory
company. The nick name for MFJ is Mighty Fine Junk. Autek also makes a
similar device although I haven't tried one. The MFJ-259B SWR analyzer is
basically a handheld impedance meter. It's also good for checking the input
Z of Bicons and such. The MFJ-269 provides a look at 470 MHz.
http://www.mfjenterprises.com/index.php

   Dave Cuthbert


From: John Woodgate [mailto:j...@jmwa.demon.co.uk]
Sent: Friday, January 31, 2003 5:14 AM
To: emc-p...@majordomo.ieee.org
Subject: Re: EN55022:1998 + A1:2000



I read in !emc-pstc that drcuthbert drcuthb...@micron.com wrote (in
cfefa50c9bcad21197470001fa7eba6b14121...@ntexchange05.micron.com)
about 'EN55022:1998 + A1:2000' on Wed, 29 Jan 2003:
And I have used an MFJ-259B (only
$260) to measure ferrites from 1.7 to 170 MHz.  

What is an MFJ-259B and where can I buy one?
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk

Interested in professional sound reinforcement and distribution? Then go to 
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!


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RE: EN55022:1998 + A1:2000

[drcuthbert]

How can a ferrite clamp be called a CMAD Common Mode Absorption Device? It
reduces EM radiation 
by reducing the current through the antenna, not by absorbing RF. It
could, however, be called a CMAD Common Mode Attenuation Device.

  Dave Cuthbert


From: John Woodgate [mailto:j...@jmwa.demon.co.uk]
Sent: Friday, January 31, 2003 5:12 AM
To: emc-p...@majordomo.ieee.org
Subject: Re: EN55022:1998 + A1:2000



I read in !emc-pstc that Gert Gremmen g.grem...@cetest.nl wrote (in
oleokfnbajjejfkplbbmoeelchaa.g.grem...@cetest.nl) about 'EN55022:1998
+ A1:2000' on Thu, 30 Jan 2003:

The official name is CMAD Common Mode Absorption Device.
(before John makes one himself ;))

You mean me?  And do you mean before I make a name for the device or
before I make a DIY device itself? I don't plan to do that at present,
but you never know.

The discussion in the UK committee leads me to think that the 'MAD' part
is apt. (;-)
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk

Interested in professional sound reinforcement and distribution? Then go to 
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!


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RE: Helmholtz article

[drcuthbert]

See the May 2002 issue


From: drcuthbert [mailto:drcuthb...@micron.com]
Sent: Friday, January 31, 2003 6:55 AM
To: emc-p...@ieee.org
Subject: Helmholtz article



Here is the link to the Conformity magazine article: Magnetic Field
Calibration: Unwinding The Helmholtz Coil, by Isidor Straus
http://www.conformity.com/featurearticlesarchive.html#June%202002

I used the formulas in this article to design and build an active ELF loop
antenna.

  Dave Cuthbert 
  Micron Technology


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Helmholtz article

[drcuthbert]

Here is the link to the Conformity magazine article: Magnetic Field
Calibration: Unwinding The Helmholtz Coil, by Isidor Straus
http://www.conformity.com/featurearticlesarchive.html#June%202002

I used the formulas in this article to design and build an active ELF loop
antenna.

  Dave Cuthbert 
  Micron Technology


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RE: single fault conditions

[drcuthbert]

Brian,
 
I believe that forcing a FET failure would be a good test but should be in
addition to the mechanical short method. If your power supply is safe for both
failure modes that would be great. The fuse should open before the failed FET
can cause a heat or fire problem. And it was already a shock hazard so that
might not be an issue. 
 
The reason I would hesitate to use only the failed FET test is that changes in
the type or manufacture or the FET could be an issue. And someone at UL might
call you on not using the mechanical short test. If an actual failed component
reveals a problem that the mechanical short does not, then the whole idea of a
mechanical short test has a problem! 
 
   Dave Cuthbert   
 
 -Original Message-
From: boconn...@t-yuden.com [mailto:boconn...@t-yuden.com]
Sent: Wednesday, January 29, 2003 2:40 PM
To: emc-p...@majordomo.ieee.org
Subject: single fault conditions



Good People of PSTC 

The environment being considered is a switching power supply. The technique
that safety agencies use to simulate a SFC on a power FET does not seem, IMHO,
to simulate the actual failure mode of the device. To wit: when the mosfet
fails short, it blows itself open; so the amount of current sucked out of
mains, e.g., the PFC FET, would probably open the component after a few input
cycles. But if I apply a direct mechanical short (source to drain), current is
being forced to flow until the fuse blows, or until some series trace or
component opens.

The Bad: some FETs fail very violently, and can actually be a fire hazard
and/or shock hazard in open-frame switchers; but if the FET itself does not
provide the short circuit, we will never know

The Good: providing a continuous (mechanical) short will reveal if there are
other components in the current path that could be cause the unit to fail in
an unsafe mode. Although, according to QA records, these components have never
failed, so it can be both demonstrated by design equations and empirical
evidence that the SFC test does necessarily demonstrate anything relevant...

The Ugly: Safety testing results in design corrections that do not increase
product safety. 

So would it be legitimate to over-drive the gate, forcing short circuit
current to flow through the FET, but not to apply a mechanical short across
the component? Experiences  comments are appreciated.

R/S, 
Brian 

RE: EN55022:1998 + A1:2000

[drcuthbert]

Chris' Maxwell equations look correct. But the point at which ferrites are
placed will not always have a common mode impedance of 50 ohms. Here's An
example: a large DUT has a 1 meter long cable that connects to the ground
plane. At 75 MHz the common mode impedance of the cable, at the DUT, is
about 3k ohms. Adding a 1k +j1k ferrite at the DUT knocks down the radiation
by 10 dB. But the radiation is not reduced mainly by losses but by
detuning the antenna. The resonant frequency has shifted from 76 MHz to
60 MHz. Now 60 MHz could be a problem. I noticed this type of thing while
trying ferrites to reduce emissions from a digital device that had a DUT
cable (not grounded at the end). I could fix one frequency with ferrites but
it would just tune the cable/system to resonance at another frequency. The
person I was working with didn't believe this theory so I ADDED wire to the
end of the DUT cable to make it 1/2 wavelength, rather than 1/4 wavelength
at the offending frequency and dropped the signal by 20 dB. 

If anyone has any changes to the model or a what-if, I can simulate it and
send you the simulated data.

Dave Cuthbert
Micron Technology


From: Pettit, Ghery [mailto:ghery.pet...@intel.com]
Sent: Wednesday, January 29, 2003 12:09 PM
To: 'Chris Maxwell'; Pettit, Ghery; neve...@attbi.com;
emc-p...@majordomo.ieee.org
Subject: RE: EN55022:1998 + A1:2000



Chris,

You can indeed make your own, but my bet is that A2LA or NIST NVLAP
inspectors will want to see calibration data, not calculations.

Now, if we just had a published calibration technique...

Ghery


From: Chris Maxwell [mailto:chris.maxw...@nettest.com]
Sent: Wednesday, January 29, 2003 10:57 AM
To: Pettit, Ghery; neve...@attbi.com; emc-p...@majordomo.ieee.org
Subject: RE: EN55022:1998 + A1:2000


Ghery,

If the standard is assuming a 50 Ohm system, doesn't this breakdown to a
simple calculation?

Insertion Loss = IL = 20 x log((50 + Zf) / 50)where Zf is the ferrite
impedance

This could easily be solved for Zf if you assume IL to be 15dB  (in this
case the dB are truely dimensionless; as you are calculating a pure loss
from an arbitrary level).

I would think that you would just have to:

1.  Solve the above for Zf.  By the way, I get 231.2 Ohms.  Can someone
check this?

2.  Gather up a box of doughnuts such that the total Zf is above the
answer for step 1 at all frequencies from 30Mhz to 1Ghz

3.  Color code the doughnuts (or whatever) and write a procedure that says
something like clamp three blue doughnuts and two red doughnuts over each
cable ...

Have I over simplified this???  Wouldn't this be proof enough for any
accreditation body?  I know that $300 may not seem like alot to some; but it
adds up after a few cables.  Besides; we went to college to learn all of
that math; why not use some of it?  I don't mind paying for stuff that I
can't make; but this one seems possible to me.

Chris Maxwell | Design Engineer - Optical Division
email chris.maxw...@nettest.com | dir +1 315 266 5128 | fax +1 315 797 8024

NetTest | 6 Rhoads Drive, Utica, NY 13502 | USA
web www.nettest.com | tel +1 315 797 4449 | 









 -Original Message-
 From: Pettit, Ghery [SMTP:ghery.pet...@intel.com]
 Sent: Wednesday, January 29, 2003 11:59 AM
 To:   'neve...@attbi.com'; emc-p...@majordomo.ieee.org
 Subject:  RE: EN55022:1998 + A1:2000
 
 
 Amendment 1 to CISPR 22:1997 (Amendment A1:2000 to EN 55022:1998) requires
 that the clamps provide at least 15 dB of loss in a 50 ohm system over the
 frequency range of 30 MHz to 1000 MHz.  The use of extension cords is
 prohibited.  Can you guarantee that your bucket of doughnuts will meet
this
 requirement?  How will you demonstrate that to your lab's accrediting
body?
 
 
 Fischer's clamps are around $300 each.  Compared with what we had to
choose
 from prior to their product, these are not big bucks.
 
 Ghery Pettit
 Intel
 
 
 
 


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 Ron 

RE: EN55022:1998 + A1:2000

[drcuthbert]

The EM radiation from wires with and without ferrite cores can be simulated
with NEC. The required parameters are: length of wire, physical orientation,
how the end is terminated (floating? To ground?, frequency, the RL model of
the ferrite). Then one can move the ferrite around to see what happens.
There are situations where a single ferrite does virtually nothing. This why
I am wary of just throwing on a ferrite and calling it good (although I have
been known to do this). The complex impedance of a ferrite can be measured
on a VNA. If a VNA isn't available an RF source, and a spectrum analyzer
will give the scalar impedance. Or lately I have used a pulse generator and
an oscilloscope to characterize ferrites for the design of wide-band time
domain transmission line transformers. And I have used an MFJ-259B (only
$260) to measure ferrites from 1.7 to 170 MHz.  

   Dave Cuthbert
   Micron Technology 


From: Chris Maxwell [mailto:chris.maxw...@nettest.com]
Sent: Wednesday, January 29, 2003 11:57 AM
To: Pettit, Ghery; neve...@attbi.com; emc-p...@majordomo.ieee.org
Subject: RE: EN55022:1998 + A1:2000



Ghery,

If the standard is assuming a 50 Ohm system, doesn't this breakdown to a
simple calculation?

Insertion Loss = IL = 20 x log((50 + Zf) / 50)where Zf is the ferrite
impedance

This could easily be solved for Zf if you assume IL to be 15dB  (in this
case the dB are truely dimensionless; as you are calculating a pure loss
from an arbitrary level).

I would think that you would just have to:

1.  Solve the above for Zf.  By the way, I get 231.2 Ohms.  Can someone
check this?

2.  Gather up a box of doughnuts such that the total Zf is above the
answer for step 1 at all frequencies from 30Mhz to 1Ghz

3.  Color code the doughnuts (or whatever) and write a procedure that says
something like clamp three blue doughnuts and two red doughnuts over each
cable ...

Have I over simplified this???  Wouldn't this be proof enough for any
accreditation body?  I know that $300 may not seem like alot to some; but it
adds up after a few cables.  Besides; we went to college to learn all of
that math; why not use some of it?  I don't mind paying for stuff that I
can't make; but this one seems possible to me.

Chris Maxwell | Design Engineer - Optical Division
email chris.maxw...@nettest.com | dir +1 315 266 5128 | fax +1 315 797 8024

NetTest | 6 Rhoads Drive, Utica, NY 13502 | USA
web www.nettest.com | tel +1 315 797 4449 | 









 -Original Message-
 From: Pettit, Ghery [SMTP:ghery.pet...@intel.com]
 Sent: Wednesday, January 29, 2003 11:59 AM
 To:   'neve...@attbi.com'; emc-p...@majordomo.ieee.org
 Subject:  RE: EN55022:1998 + A1:2000
 
 
 Amendment 1 to CISPR 22:1997 (Amendment A1:2000 to EN 55022:1998) requires
 that the clamps provide at least 15 dB of loss in a 50 ohm system over the
 frequency range of 30 MHz to 1000 MHz.  The use of extension cords is
 prohibited.  Can you guarantee that your bucket of doughnuts will meet
this
 requirement?  How will you demonstrate that to your lab's accrediting
body?
 
 
 Fischer's clamps are around $300 each.  Compared with what we had to
choose
 from prior to their product, these are not big bucks.
 
 Ghery Pettit
 Intel
 
 
 
 


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RE: EN55022:1998 + A1:2000

[drcuthbert]

I don't have a copy of EN55022 to look at so I'll ask a question: How many
ferrite clamps and what type are specified? And are they placed at various
places, at one location only, or placed as with a Bicon balun?

Dave Cuthbert
Micron Technology 


From: richwo...@tycoint.com [mailto:richwo...@tycoint.com]
Sent: Tuesday, January 28, 2003 11:30 AM
To: emc-p...@majordomo.ieee.org
Subject: EN55022:1998 + A1:2000



A1 to EN55022:1998 requires the use of ferrite clamps on all cables leaving
the table-top EUT for a connection outside the test site. Are there any
other manufacturers of these clamps other than Fischer Custom
Communications?

Richard Woods
Sensormatic Electronics
Tyco International



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RE: Acoustic noise calculations for multiple shelves

[drcuthbert]

But in the end it doesn't matter, does it? A dB is a dB. An increase in SPL
of 6 dB is the same as an increase in sound power  of 6 dB. Just like a 6dB
change in voltage results in a 6dB change in power. Wonderful things, those
dB's..

   Dave Cuthbert
   Micron Technology


From: drcuthbert [mailto:drcuthb...@micron.com]
Sent: Thursday, January 23, 2003 8:51 AM
To: 'Hudson, Alan'; EMC-pstc (E-mail)
Subject: RE: Acoustic noise calculations for multiple shelves



Alan,

here is a definition of dBa:
dBa: Abbreviation for decibels adjusted. Weighted absolute noise power,
calculated in dB referenced to 3.16 picowatts (-85 dBm), which is 0 dBa.
(188) Note: The use of F1A-line or HA1-receiver weighting must be indicated
in parentheses as required. A one-milliwatt, 1000-Hz tone will read +85 dBa,
but the same power as white noise, randomly distributed over a 3-kHz band
(nominally 300 to 3300 Hz), will read +82 dBa, due to the frequency
weighting. Synonym dBrn adjusted. From this link:
http://www.its.bldrdoc.gov/fs-1037/dir-010/_1471.htm

Now here is a definition of SPL:
Sound Pressure Level:
The sound pressure level at a point is measured in decibels (dB) and is
equal to 20 times the logarithm to the base 10 of the ratio of R.M.S. sound
pressure to the reference sound pressure. The reference sound pressure in
air is taken to be 2 * 10-5 Pa. From this link:
http://www.camets.com.au/info/glossary/spl.htm

Is this where some of the confusion is coming from? Some are thinking of
sound pressure and others are thinking in terms of sound power. 

   Dave Cuthbert
   Micron Technology







From: Hudson, Alan [mailto:alan.hud...@amsjv.com]
Sent: Thursday, January 23, 2003 2:15 AM
To: EMC-pstc (E-mail)
Subject: RE: Acoustic noise calculations for multiple shelves



John Woodgate wrote:
 The noises are uncorrelated (largely), so you add 3 dB, not 6.

Now I'm confused! I always thought it was noise *level* (similar to voltage
level) not noise *power*, and hence it was 20*log(ratio) not 10*log(ratio).
So I've been using 6dB for doubling noise, not 3dB.

I'll need to consult some basic texts, methinks.

Regards,

Alan
-- 
Remove .paper-bag from address if replying by email.




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RE: CALIBRATION AND CONSTRUCTION OF HELMHOLTZ COILS

[drcuthbert]

Gordon,

the May 2002 issue of Conformity magazine had an excellent article on
Helmholtz coils. I checked their website but didn't see how to access old
issues. If you can't get a copy online I will be glad to FAX you a copy of
the article. To put things in perspective we can think about the field
around an infinite length wire. Say the wire has a current of 1 ampere and
the point of measurement is 1 meter away. The field H is (1A)/(2Pi meters)=
0.16 A/m. Now B=uH and u = 1.256uH/m. So, B= (1.256uH)(0.16A/m) = 200nT. To
obtain 5mT one would need 25,000 amps with this arrangement! Let's do a
Helmholtz: H = 1.43(nI/d) where d is the diameter of the circular coil. The
coils are spaced one diameter. For coils with a diameter of 1 meter, one
turn, and one ampere the field H is 1.43 A/m. You need about 4000 A/m for
5mT. Lots of amps. How about 200 turns at 20 amps? That will do it. So, two
1-meter coils with 200 turns of #12 AWG wire with 20 amps flowing. The
resistance at 100 deg C is about 10 ohms, so 200 VDC is needed. 2000 watts.
Smokin!!   

   Dave Cuthbert
   Micron Technology 

  


From: Gordon,Ian [mailto:ian.gor...@edwards.boc.com]
Sent: Thursday, January 23, 2003 8:15 AM
To: 'IEEE EMC-PSTC GROUP'
Subject: CALIBRATION AND CONSTRUCTION OF HELMHOLTZ COILS



All
I would like to construct a Helmholtz coil to perform magnetic field
immunity testing at DC frequencies and thus simulate the effect of a
permanent magnet. There are some details on construction in EN61000-4-8
which details power frequency magnetic field immunity testing within the
scope of the EMC directive. However the fields referred to are measured in
A/m, whereas I need a field of, for example, 5mTesla.
Can anybody advise me as to how to construct such a coil with a test volume
of 0.5 x 0.5 x 0.5m and a field of 5mTesla?
Thanks
Ian Gordon
 

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helmholtz

[drcuthbert]

The resistance is about 20 ohms, and not 10 ohms. Now you needed 400 volts
to obtain 20 amps through the two coils in series. Or, run them in parallel
with 200 volts. This might be off a bit but I get 5 mN for the force between
the two coils. So, they aren't going to tear the setup apart. Almost a 5000
foot spool of wire needed per coil. This looks like a fun project.

   Dave Cuthbert




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ESD

[drcuthbert]

This probably comes under the heading of due diligence. 

   Dave Cuthbert



Kris,

In my reading of the standard, and the next modification will include
that clearly, you need to test discharges to the shell of the USB
connector, as there will not be a connector in there all the time.

There is another strong argument: The user might plug a charged (e.g.
hand-held) device into the USB port.

Of course, the main criteria is survival, as you cannot test
connectivity if there is no USB device.

But if you have multiple USB connectors, another USB device might loose
connection when discharging to a different USB connector.

David Pommerenke



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RE: Acoustic noise calculations for multiple shelves

[drcuthbert]

Quite right for uncorrelated noise. 

To add to this discussing we can think about the response of the human ear
to sound
level. A 3 dB increase in SPL does not sound twice as loud. If I 
remember correctly it takes a 6-8 dB increase to sound twice as loud. So
is the
goal to meet a standard or for operator comfort? 

  Dave Cuthbert
  Micron Tech


From: Ken Javor [mailto:ken.ja...@emccompliance.com]
Sent: Wednesday, January 22, 2003 10:56 AM
To: Luttrell, Lyle; 'Gandler, Mark'; emc-p...@majordomo.ieee.org
Subject: Re: Acoustic noise calculations for multiple shelves



I would further amplify on this comment.  It is not just a 10 log vs. 20 log
calculation.  Sound power is the quantity of interest, so by definition it
is a 10 log relationship .  But someone said add 3 dB for each added
component.  That is incorrect.  You only add 3 dB for the second component.
The issue is that the sound pressure level (exclusive of localized
interference effects) adds as the square root of the sum of the squares.
And that is what you get when you use 10 log(number of units).


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[no subject]

[drcuthbert]

I 'm afraid that my response to Neven's comments concerning EFT might have
sounded like I didn't approve of his method. Far from it, I think his method
is sound. I added my comments about component value selection as an aside.
Keep up the good work.

Dave Cuthbert
Micron Technology 


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RE: SV: NRTL in the U.S.

[drcuthbert]

Amund,

Several EU standards have been harmonized with the United States UL
standards. A list can be found at
http://ulstandardsinfonet.ul.com/catalog/stdscatframe.html

For example, UL 60950 the same as EN 60950. So, I'm thinking that if your
device meets EU safety requirements it will make it through UL as long it
has been designed to a harmonized standard. Does this sound reasonable to
anyone or am I off the mark?

  Dave Cuthbert


From: Amund Westin [mailto:am...@westin-emission.no]
Sent: Friday, January 17, 2003 12:25 PM
To: emc-p...@majordomo.ieee.org
Subject: SV: SV: NRTL in the U.S.



I would never dare to declare U.S. compliance without testing and certify
via a NRTL. But what I am struggling with, is to gain knowledge about the
basic electrical safety laws in U.S. Maybe I do not need legally to go
through a NRTL, but that does not mean I would, even if I could.

The electrical safety legislation seems to be a bit more complicated in U.S.
compared to EU.

Best regards
Amund Westin, Oslo / Norway



 -Opprinnelig melding-
 Fra: owner-emc-p...@majordomo.ieee.org
 [mailto:owner-emc-p...@majordomo.ieee.org]På vegne av John Woodgate
 Sendt: 17. januar 2003 13:25
 Til: emc-p...@majordomo.ieee.org
 Emne: Re: SV: NRTL in the U.S.



 I read in !emc-pstc that Amund Westin am...@westin-emission.no wrote
 (in lfenjlpmmjbmhpeibnilaeapckaa.am...@westin-emission.no) about 'SV:
 NRTL in the U.S.' on Fri, 17 Jan 2003:

 Just for a few seconds forget the customers requirements, is it
 therefore a
 correct interpretation that electrical equipment (ITE, household
 appliances,
 radio transmitters, etc) must be certified in order to follow
 the U.S. laws

 I think you really already had the strictly correct answer, but it's
 over-complicated.

 The practical answer is that it's much better to have certification than
 not to have it, unless the cost of certification would make your product
 uncompetitive against other, uncertified products in competition with
 yours.
 --
 Regards, John Woodgate, OOO - Own Opinions Only.
http://www.jmwa.demon.co.uk
Interested in professional sound reinforcement and distribution? Then go to
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!


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RE: I2C bus sensitivity to EFT

[drcuthbert]

On the subject of adding caps in circuits for noise immunity. Rather than
just throwing in a value of 0.1 uF, finding it works, and calling it good I
like to use a different approach. Determine the lowest value that will fix
the immunity problem. Then find the largest value that will still allow the
circuit to function properly. Then specify a value somewhere in between;
possibly the geometric mean. In this way you are not using a value next to
a cliff that will cause some malfunction in a production run. In a high
volume product just throwing in a value and calling it good is EXTREMELY
poor engineering.

   Dave Cuthbert
   Micron Technology


From: neve...@attbi.com [mailto:neve...@attbi.com]
Sent: Thursday, January 16, 2003 8:19 PM
To: emc-p...@majordomo.ieee.org
Subject: Re: I2C bus sensitivity to EFT



I have never worked on design of a product with external I2C bus, but 
considering the bus speed of 100 kHz to 3.4 MHz (depending on type) relative
to 
about 60-100 MHz BW (depending on definition) of EFT, you may try killing
good 
portion of EFT with ceramic caps.

Be sure that the cable shield is connected on both ends.

Also, check for the possibility that the EFT may couple to some other 
apparently non-critical pin of the IC and then internally cause
susceptibility. 
The first suspect in such case would be the reset pin, but often you can be 
surprised that other pins may cause problems. I just had a case in which EFT

would couple to the LED driver on an Ethernet device and cause problems 
internally in the chip, leading to packet loss. A cap on the LED driver pin 
fixed the problem !! :)

Neven
 
 Hi Forum,
 Has anyone on this forum worked with I2C products and maybe be able to
 advise on the best method to suppress EFT noise that would alow the I2C
bus,
 via external cables, to operate as expected e.g. Good EFT devices? How
best
 to shield the I2C? Other?
 As always I look forward to your proffesional advice.
 History
 I have a system that connects 3 products (powered from an in-line external
 non-earthed power supply, SELV) using the I2C bus via a 1m shielded and 1m
 shielded curly cable. I use an I2C bi-directional extender IC P82B715 on
one
 of the products. The I2C protocol gets corrupted when I appply the
 Electrical Fast Transient (EFT) Test per the EMC Standard EN61000-4-4.
 I have tried shielded cables, several EFT devices and 1nF caps on the
lines
 but with little affect.
 
 Kind Regards
 Alex McNeil
 Principal Engineer
 Tel: +44 (0)131 479 8375
 Fax:+44 (0)131 479 8321
 email: alex.mcn...@ingenicofortronic.com
 
 
 ---
 This message is from the IEEE EMC Society Product Safety
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RE: Is this a case of basic insulation?

[drcuthbert]

I assume this is an off line switcher. If so, the FET is at mains potential
and the required creepage and clearance distances is the same as the
hot-to-ground creepage requirement(4 mm or is it 3 mm? for creepage).

I would not use the chassis as a heatsink myself. Even dirt cheap PC power
supplies don't do this. But if you must, is a heatsink pad defined as single
insulated? You might need two pads to constitute double insulation. Another
route is to use a full-pack FET (already encased in an insulating material)
along with a pad. But do we define creepage under the assumption that one
insulation layer has a defect? If so then the full-pack and pad will not do
if we assume that the pad has a defect. 

The FET could be held with a clamp of some sort. This FET-insulation-chassis
arrangement will have quite a bit of thermal resistance You can calculate
this and might find that you are better off thermally and cost-wise with a
small heatsink attached directly to the FET and floating at mains potential.
To reduce the E-field noise being thrown around, by the heatsink connected
to the FET Drain, you can use a full-pack FET and connect the heatsink to
the floating circuit common. In this case you will not need a pad and I
wouldn't bother with heatsink paste. A package such as a TO220 or TO218,
when mounted on a flat heatsink, will work just fine without that messy
paste. I also wouldn't worry about the junction temp if it is 100 C and even
125 C is acceptable. I see engineers spending too much time and money trying
to keep junction temperatures luke warm. I can get into a whole page on
reliability in the real world (and how to calculate it and how some methods
are bogus) but will spare you at this time.

Dave Cuthbert
Micron Technology 


From: Peter L. Tarver [mailto:peter.tar...@sanmina-sci.com]
Sent: Friday, January 17, 2003 8:26 AM
To: EMC-PSTC (E-mail)
Subject: RE: Is this a case of basic insulation?



Vic -

Your assumption that at least Basic insulation is required
is correct.  However, creepage distances are based on rms
voltages, not peak.

The below assumes that the voltages you mentioned are
present on the heatsink of the FET.

Assuming that a true rms meter will indicate an rms voltage
between 250 Vrms and 300 Vrms, the minimum require creepage
from Table 2L is 3.2 mm.

Based on the peak voltage you mentioned, the minimum
required clearance distance from Table 2H is 2.0 mm, plus
the added distance from Table 2J of 0.2, gives a total
minimum clearance distance of 2.2 mm.

Without knowing the particulars of the FET and its heatsink
in any great detail, an insulating pad is an appropriate and
common means of complying with the standard.  Unless you can
demonstrate that the pad will not compress to less than 3.2
mm thickness in the application, you'll probably need a
shouldered washer or something similar to add additional
creepage between the screw shank and the FET's heatsink.

Polymeric screws are available, but I can't speak regarding
their use in an elevated temperature.


Regards,

Peter L. Tarver, PE
Product Safety Manager
Sanmina-SCI Homologation Services
San Jose, CA
peter.tar...@sanmina-sci.com


 -Original Message-
 From: Gibling, Vic
 Sent: Friday, January 17, 2003 12:00 AM


   We drive a FET based H-bridge from
 rectified 230VAC mains; thus
 320Vpk across the bridge. We have assumed the
 insulation between the
 rectified power return and chassis (Class 1
 product) is basic, thus
 requiring 4mm creepage (IEC950). The proposed
 FETs need to be attached to a
 heat sink and we would like to use the chassis
 for this purpose.

   Our problem is that the FETs have around
 2mm creepage between their
 exposed heatsink surface and the fixing screw,
 insufficient to meet the
 basic insulation creepage distance.

   Is our interpretation regarding basic
 insulation correct/reasonable?

   If we use an insulative thermal pad between
 the FET and chassis,
 does the compression of the pad exclude the air
 path thus offering
 sufficient protection? I am aware of such pads
 offering 4.5kV breakdown.

   Thank you

 Vic Gibling
 Compliance Engineer

 e2v technologies Ltd
 Waterhouse Lane
 Chelmsford
 ESSEX CM1 2QU

 Telephone:  +44 (0) 01245 493493
 Direct Line:  +44 (0) 01245 453352
 Facsimile: +44 (0) 01245 453410

 E-mail:   vic.gibl...@e2vtechnologies.com
 Internet:  www.e2vtechnologies.com



 ---
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RE: NRTL in the U.S.

[drcuthbert]

Does this apply to in-house test equipment? That is, equipment that is built
in-house and remains on site? In the past I have designed in-house equipment
to meet the safety standards but did not send the equipment out for testing
and certification.

   Dave


From: Gregg Kervill [mailto:gr...@test4safety.com]
Sent: Tuesday, January 14, 2003 7:50 AM
To: 'Joe P Martin'; emc-p...@majordomo.ieee.org
Subject: RE: NRTL in the U.S.
Importance: High



Joe,

You are correct that NRTL LISTING is a specified requirement by some cities
and states.

You are incorrect in that all products used where OSHA applies are required
to be NRTL LISTED.

NEC Code makes that same requirement

Furthermore most (I have yet to find an exception) cities and states base
their code upon NEC


There may be local exception but I believe that to make a 'blanket statement
that .. NRTL is not required in the US... is I believe at best confusing
and at that the worst very dangerous.

The following is a statement from the US NOL:

All electrical equipment, except those kinds which no NRTL accepts,
certifies,
lists, labels, or otherwise determines to be safe, must be approved, as
that term
is defined at 29 CFR 1910.399. Except as indicated in the following this
means
that a NRTL must accept, certify, label, list, or otherwise determine that
equipment is safe for it to be considered approved.

The requirement mandating that electrical equipment be approved is set
forth at
29 CFR 1910.303(a). Also, OSHA Standard 29 CFR 1910.303(b)(2) requires that
approved equipment be used in conformance with its approval.

Electrical equipment which no NRTL accepts, certifies, lists, labels, or
determines to be safe is acceptable to OSHA under the following if the
equipment is inspected or tested by another Federal Agency, or by a State,
municipal, or other local authority responsible for enforcing occupational
safety
provisions of the NEC and found in compliance with the provisions of the NEC
as
applied to Subpart S of 29 CFR 1910 standards.

Custom made equipment which is designed, fabricated for, and intended for
use
by a particular customer does not have to be approved if it is determined to
be
safe for its intended use by its manufacturer. The determination must be
made
on the basis of test data that the employer keeps and makes available to the
Assistant Secretary of Labor for OSHA.

In summary then if there are ten different models of a particular kind of
equipment, but only one of them is accepted, certified, listed, labeled or
otherwise determined to be safe by a NRTL only that one would be considered
to
be approved; unless of course it is custom made equipment.

Only those entities that have applied and been approved pursuant to the
requirements of 29 CFR 1910.7 are considered to be a NRTL. Recently the
Canadian Standards Association was the first foreign laboratory approved
as
an NRTL. Enclosed find a copy of a directive that discusses NRTLs.


Best regards

Gregg Kervill

Gregg Kervill DipIM, MIMgt, MIEEE
VP Engineering
Test4Safety.com Inc
PO Box 310,
Reedville, VA
22539. USA
Phone  ( 804) 453-3141
Fax(804) 453-9039
http://www.test4safety.com/


From: owner-emc-p...@majordomo.ieee.org
[mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of Joe P Martin
Sent: Monday, January 13, 2003 11:22 PM
To: emc-p...@majordomo.ieee.org
Subject: NRTL in the U.S.


Greetings,

As has been discussed in previous threads, NRTL Listing is not a
requirement to sell electronic products in the U.S.  However, there are
cities, counties, etc. within the U.S. that do require NRTL Listing.
These include Los Angeles and Chicago.  Does anyone have a comprehensive
list of all the cities, counties or states that do require NRTL Listing.

Any and all comments are appreciated.

Regards

Joe Martin
Applied Biosystems
marti...@appliedbiosystems.com




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RE: Fiber optic cable testing per EN 55022:1998 ?

[drcuthbert]

From: John Woodgate [mailto:j...@jmwa.demon.co.uk]
Sent: Saturday, January 11, 2003 5:33 AM
To: emc-p...@majordomo.ieee.org
Subject: Re: Fiber optic cable testing per EN 55022:1998 ?



I read in !emc-pstc that drcuthbert drcuthb...@micron.com wrote (in
cfefa50c9bcad21197470001fa7eba6b14121...@ntexchange05.micron.com)
about 'Fiber optic cable testing per EN 55022:1998 ?' on Fri, 10 Jan
2003:

Chris,
some excellent points! My take on this is that a fiber optical cable has a
cutoff frequency that is way above the RF frequencies we are concerned
with. It just won't act as a waveguide for what we consider RF wavelengths.
However, I think the optical cable certainly does leak a bit at light
wavelengths. 

That's a surprise; what evidence do you have?

Dave: Evidence for the cutoff frequency of the cable or that it can leak? 
For the cutoff frequency the evidence is supplied by the formulas that
describe waveguides. 
For the optical leakage my evidence is only empirical. I have noticed
leakage
when playing with optical fibers. 

It seems like one could perform light emissions and
susceptibility testing. Now most of our light wave communications use
cables. Sort of like if all RF communications was done in copper. With
nothing intentionally radiated, and with the cables operating as very poor
antennas, we might have no need for emission and susceptibility testing. On
the other hand, the FCC does not regulate radiated optical communications.
Maybe it's time to do so. With laser range finders, optical radar, IR
remote
control, and other primitive devices we are accumulating pollution of this
part of the EM spectrum. Reminds me of spark transmitters spewing RF over a
wide frequency range.

Street lights are the spark transmitters of the visible spectrum.


Shouldn't an optical cable with a metal sheath be treated just like any
other cable? Hook it up during EMC testing?

Yes, ALL cables, of whatever sort, are to be connected during testing.

And as you point out, where is the transition from RF to light? RF
generation methods (such as gyrotrons, seem to peter out at wavelengths of
1000 microns while visible light begins at 0.7 microns. There seems to be a
huge no man's land in the EM spectrum. 

Look up 'far infra-red'. This part of the spectrum is flooded with
thermal radiation from objects at normal temperatures. But sources and
detectors do exist.
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk

Interested in professional sound reinforcement and distribution? Then go to 
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!


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RE: Fiber optic cable testing per EN 55022:1998 ?

[drcuthbert]

I don't think an EM wave is affected by another magnetic or electric field.
There is no mixing in a vacuum (and CFA antennas don't exist). And I guess
you are correct on charge creating an EM wave. A positive hydrogen atom
would work (I think) and it has no electron. Acceleration of charge is
required- not just velocity- to create the time-varying magnetic field from
which EM radiation springs.

   Dave Cuthbert
   Micron Technology

From: Peter L. Tarver [mailto:peter.tar...@sanmina-sci.com]
Sent: Friday, January 10, 2003 2:53 PM
To: PSTC
Subject: RE: Fiber optic cable testing per EN 55022:1998 ?



You're partially correct, Ken.  However, the photon (in
quantum mechanics) is the particle that mediates the
electromagnetic force; photon also the name given to the
particle that is a quantum of electromagnetic energy.  Thus,
photons are involved as the particle analog to an
electromagnetic wave.  Also, an electron beam is not
identical to an electromagnetic wave in the sense you are
trying to characterize them.

The primary difference between bosons (photons are bosons)
and fermions (which leptons are classified as; electrons are
leptons) is boson have integer spins, while fermions have
fractional spins (spin is a classification of intrinsic
angular momentum) and bosons are not constrained by the
Pauli Exclusion Principle, whereas fermions are.

This does not address why an electromagnetic wave of longer
wavelength may be redirected by the presence of an external
magnetic or electric field, while light is less affected.

More properly, it is not an electron that creates an
electromagnetic wave, it's charge; electrons just happen to
possess a quantum of electric charge.  An electric charge at
rest radiates an electric field.  An electric charge in
motion creates a magnetic field, irrespective of
acceleration.

Theoretically, it should be possible to magnetically or
electrically redirect light.

By definition, light is visible and exists only between the
wavelengths of 700 nm-400 nm.  Light and optical
radiation has been extended to other wavelengths (ir and
uv) in the common vernacular mostly because of lasers
being used at those wavelengths.



Regards,

Peter L. Tarver, PE
Product Safety Manager
Sanmina-SCI Homologation Services
peter.tar...@sanmina-sci.com


 From: Ken Javor
 Sent: Friday, January 10, 2003 9:24 AM

 The answer is independent of frequency, it is the
 nature of the particle
 (electron vs. photon) that is key.  I have
 forgotten the terminology, but
 one type  of particle is called a boson, and per
 my (quite possibly faulty)
 recollection, bosons do not interact with
 electromagnetic fields.  For
 example, you can use either an electric or
 magnetic field to deflect and
 point an electron beam, but you cannot do so with
 a beam of light.




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RE: Fiber optic cable testing per EN 55022:1998 ?

[drcuthbert]

Chris,
some excellent points! My take on this is that a fiber optical cable has a
cutoff frequency that is way above the RF frequencies we are concerned
with. It just won't act as a waveguide for what we consider RF wavelengths.
However, I think the optical cable certainly does leak a bit at light
wavelengths. It seems like one could perform light emissions and
susceptibility testing. Now most of our light wave communications use
cables. Sort of like if all RF communications was done in copper. With
nothing intentionally radiated, and with the cables operating as very poor
antennas, we might have no need for emission and susceptibility testing. On
the other hand, the FCC does not regulate radiated optical communications.
Maybe it's time to do so. With laser range finders, optical radar, IR remote
control, and other primitive devices we are accumulating pollution of this
part of the EM spectrum. Reminds me of spark transmitters spewing RF over a
wide frequency range.

Shouldn't an optical cable with a metal sheath be treated just like any
other cable? Hook it up during EMC testing?

And as you point out, where is the transition from RF to light? RF
generation methods (such as gyrotrons, seem to peter out at wavelengths of
1000 microns while visible light begins at 0.7 microns. There seems to be a
huge no man's land in the EM spectrum. 


  Dave Cuthbert
  Micron Technology


From: Chris Maxwell [mailto:chris.maxw...@nettest.com]
Sent: Friday, January 10, 2003 8:24 AM
To: emc-p...@majordomo.ieee.org
Subject: RE: Fiber optic cable testing per EN 55022:1998 ?



OK,

Enough of this regulatory blah, blah, blah...(although that's what we get
paid for).  How about a hypothetical question...

Typical radiated emissions measure a time varying electric field produced by
the acceleration of electrons.  When electrons accelerate back and forth at
a given frequency; then you get EM (ElectroMagnetic) radiation at that
frequency.  At these frequencies, we have electron flow in conductors.  The
electron acceleration in one conductor (say your computer backplane) gives
off an EM field which will cause a similar electron flow in another
conductor placed some distance away (the measurement antenna).  Notice that
in this case, we don't have electrons changing energy states, we just have
free electrons flowing and accelerating.  

Fiber optic cables carry light, which is modeled as photons produced by
electrons changing energy states.  We still can model this with similar wave
equations as used for any old EM radiation; but here we have radiation flow
in an insulator.  We also throw in the concept of photons whereby we try
to quantize the radiation.   Light won't (appreciably) flow at all in a
conductor.   So, we don't consider fiber optic cables to be susceptable to
EMI; and we don't consider them to give off EMI.  I think that we all
agree that trying to measure the conducted or radiated emisions from
fiber optic cables is not required by any standard.   They do conduct
light; but it is a conduction of photons; not the conduction of free
electrons that the standards try to measure.

However, I can think of some lower frequencies (lower than light, that is)
that use dielectric waveguides similar to fiber optics; yet they produce and
are susceptable to EMI.  For example, many GPS antennas us dielectric
waveguides at the GPS frequency (about 1.5GHz, if I recall correctly)

So where is the crossover point?  Does it have to do with skin depth?
Maybe the photoelectric effect?  Why don't we talk about photons at 1Ghz?
Is it just because we don't have a material with the correct band gap to
produce a 1Ghz photon?   On the other hand, can free electrons be
conducted at light frequencies; or isn't there a material with enough of a
skin depth at such frequencies?   Anybody want to take a stab at
enlightening(no pun intended) us all on this one?  I guess I'm just too lazy
to brush up on my quantum mechanics.  It's too bad that Einstein died before
we came up with listservers.  I have about a million questions for him.  He
probably would have taken a job as an EMC guy just to pay the bills while he
was working on relativity.

Sure, its a hypothetical question; but it may provide a deeper understanding
of why we don't throw fiber optic cables in the coupling clamp.

I can smell the collective cranial smoke from the group already.  That's
good.

Inquizzitively and antagonistically,

Chris Maxwell | Design Engineer - Optical Division
email chris.maxw...@nettest.com | dir +1 315 266 5128 | fax +1 315 797 8024

NetTest | 6 Rhoads Drive, Utica, NY 13502 | USA
web www.nettest.com | tel +1 315 797 4449 | 






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RE: European 3 Phase

[drcuthbert]

Bob,

here is a website with good info on this subject:
http://www.ita.doc.gov/td/machinery/ecabroad/

This link came from this site
http://users.metro2000.net/~purwinc/seec2_2.htm

which has some more links.

   Dave Cuthbert
   Micron Technology Signal Integrity group


From: rehel...@mmm.com [mailto:rehel...@mmm.com]
Sent: Wednesday, January 08, 2003 7:13 AM
To: emc-p...@majordomo.ieee.org
Subject: European 3 Phase



What three-phase voltages are commonly available in Europe? Is 230 VAC
three-phase readily available? Is wye or delta most common or doesn't it
matter?

Thanks,
Bob Heller
3M EMC Laboratory, 76-1-01
St. Paul, MN 55107-1208
Tel:  651- 778-6336
Fax:  651-778-6252
===



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RE: RF in Fluids

[drcuthbert]

Steve,
can you provide more details such as:
The type of fluid and the conductivity
The physical relationship between your equipment and the application?
How is the fluid piped?
The RF frequency?
What is the symptom that you observe?
 
Here is my first thought assuming that the chiller pipes the fluid to and
from the application through non-conductive hose and that the fluid is
conductive. Yes the fluid could provide a conductive path for RF. To
prove/disprove this theory the impedance of the suspected RF path could be
temporarily altered by:
Changing the fluid type
Placing a wire connecting the chiller to the application and running along
the tubing 
Placing ferrite cores over the tubing
 
Then see if there is a change in the symptom. Or, the RF current flowing in
the fluid can be measured with a clamp-on RF ammeter over the tubing. 
 
   Dave Cuthbert
 
 
-Original Message-
From: STEVEN BRODY [mailto:sbr...@prodigy.net]
Sent: Friday, December 27, 2002 8:33 AM
To: emc-p...@majordomo.ieee.org
Subject: RF in Fluids



We have a chiller installed in a customer application where RF is used in
their process, but we believe RF is being transmitted to our product via the
fluid.  Soe anh one have any suggestions on how to measure RF in fluids -
type of equipment, etc.?

Thanks in advance and best wishes o the EMC/PSTC Family for a happy and
healthy holiday season,

Steve Brody ( sbr...@prodigy.net mailto:sbr...@prodigy.net )

  

applied microwave mag

[drcuthbert]

For those of you who subscribe to Applied Microwaves and Wireless magazine,
they ceased publication in September. And another long time magazine has
gone belly up. Poptronics (a combination of the two magazines; Popular
Electronics and Electronics Now), a very old hobby magazine, is gone.

   Dave C

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RE: Fire Enclosure Design for NiCad Batteries

[drcuthbert]

Peter,
I would begin by reviewing the construction of CE-marked portable tool
battery packs. Things such as UL-94V material, fuses, wiring, and so on.
Then see how this applies to the soft enclosure you are contemplating. I
would be concerned about what happens when the pack/cells are damaged
through an accident, misuse, abuse, etc. For example:

What type of physical impact test is required.
What happens to the pack when one falls on it from a great height.
If a cell ruptures does the polymeric material contain the corrosive
materials.

I recently ran my portable drill from an automobile battery and when the
drill stalled the clip leads went up in smoke. Perhaps a resettable fuse
device is needed. I know I'm deviating from the question of the polymeric
material but I thought I'd put in my two cents worth.

 Dave 

-Original Message-
From: Peter Merguerian [mailto:pmerguer...@itl.co.il]
Sent: Tuesday, December 17, 2002 3:11 AM
To: EMC-PSTC (E-mail) 
Subject: Fire Enclosure Design for NiCad Batteries 



Hello All,
A battery belt made up of polymeric material similar to the one used to
manufacture school bags, consists of NiCad batteries. The battery belt is
to be used by builders in powering their battery tools during building
construction. The NiCad batteries are made of nickel plated steel, with a
thickness of 0.4 mm for the can and 1.2 mm for the cover. The 2 parts are
insultated with a polyamide insulator ring. 
Can this construction of the batteries serve as the fire enclosure or should
a separate enclosure of more robust construction be made for the batteries?

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PETER S. MERGUERIAN
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RE: Euro AC Power Source

[drcuthbert]

Sam,
concerning the 60 volts of bleed-over: I'm assuming the 230 volt outputs of
the 1:2 transformer are floating and the 60 volts was measured between one
transformer output line and PE GND using a DMM (10 M ohm input). If this is
so, this indicates a primary-to-secondary capacitance of a few hundred pF,
which is expected from this type of transformer. Since you will be
connecting one of the transformer output lines to PE the problem is taken
care of.
 
   Dave Cuthbert
   Micron Technology
 
 
-Original Message-
From: Sam Wismer [mailto:swis...@acstestlab.com]
Sent: Monday, December 16, 2002 8:07 AM
To: EMC Forum
Subject: Euro AC Power Source


Hi Group,
It's been a long time since my last post.  Hope everyone has been well.
 
We have a several AC power sources that can provide 230Vac/50Hz power.  Only
one however provides true Euro power in that it provides 230VAc on the line
side.  This unit only has around 6 amps of capacity.  We need to be able to
provide at least 20amps.  
 
We have 2 other units with higher current capacity, but the 230 Volts can
only be provided via 115V on L1 and L2 to ground.  I have been told by some,
that using this power source is acceptable for emissions and immunity
testing.  I'd like some feedback on that.  I can justify it, perhaps, for
radiated emissions, radiated fields, ESD and perhaps magnetic fields, but I
am skeptical that this would be okay for AC mains testing that apply
immunity at various phase angles and also for EN 61000-3-2 and -3.  Any
comments?
 
Another question, we have tried using a 2:1 transformer to step up the 115,
but we end up with about 60Volts of bleed over to the other line.  Is this
typical of transformers?  Anyway to prevent this?
 
 
 
Kind Regards,
 
 
Sam Wismer
Engineering Manager
ACS, Inc.
 
*Tel: (770) 831-8048
*Fax: (770) 831-8598
*Web:   http://www.acstestlab.com www.acstestlab.com
 mailto:*swis...@acstestlab.com *swis...@acstestlab.com