Re: [PSES] EN 302 195 Distance Conversion Factor

[John Woodgate]

There are two aspects to this:

 1. What will satisfy the EU authorities?

 2. What is the best that electrical science can do in this notoriously
complex situation?

I  addressed the first question. It's obvious that if no emission can be
detected at 3 m, the product passes the requirements, but  a little more
'rationale' is required, to legitimize the proof measurements at 1 m.  After
all, the reason why no emission were measured at 3 m might be because the
product wasn't working! 

The applicable standard doesn't cover the case of very weak emissions, but
another similar standard does, so it's quite reasonable to use its
extrapolation provision for the legitimizing statement. " If it's good
enough for one harmonized standard, it's good enough for another."

Others have attempted to answer the second question in several ways.
Nothing wrong with that, except that nothing seems to be definite enough, or
accessible enough, to convince a market surveillance officer that the
product is acceptable. So it doesn't really help the enquirer.

With best wishes DESIGN IT IN! OOO – Own Opinions Only
www.jmwa.demon.co.uk J M Woodgate and Associates Rayleigh England

Sylvae in aeternum manent.


-Original Message-
From: Ralph McDiarmid [mailto:ralph.mcdiar...@schneider-electric.com] 
Sent: Wednesday, December 7, 2016 10:24 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] EN 302 195 Distance Conversion Factor

I've kept the 6 volume set of the EMC Handbook, by Donald White Consultants,
for many years.   It's a good reference.

Some standards tell you what to do for correction at different measurements
distances.  If 3 metres still showed no signal, I'd use amplification and
then carefully check for overloading.  (esp if at an OATs or in situ)


Ralph McDiarmid
Product Compliance
Engineering
Solar Business
Schneider Electric



From: Ken Javor [mailto:ken.ja...@emccompliance.com]
Sent: Wednesday, December 07, 2016 9:03 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] EN 302 195 Distance Conversion Factor

Re Don White. That math was for an electrically short dipole: short relative
to wavelength, and short relative to the separation between it and the point
of observation. Neither of these criteria are obtained at one meter, and
therefore the math is not useful.

What I just said is what Gert said earlier, much more elegantly.  And
English is my first language...

Ken Javor
Phone: (256) 650-5261


From: Ed Price <mailto:edpr...@cox.net>
Reply-To: Ed Price <mailto:edpr...@cox.net>
Date: Tue, 6 Dec 2016 05:56:12 -0800
To: <mailto:EMC-PSTC@LISTSERV.IEEE.ORG>
Subject: Re: [PSES] EN 302 195 Distance Conversion Factor

As Gert points out, extrapolation is fraught with hazards of assumptions. If
you absolutely must attempt to extrapolate data from extreme distances, like
a 1-meter measurement to a 10-meter equivalent field, you should test the
sanity of your extrapolation algorithm.

For instance, it has been said that, at 10 meters, the emissions could not
be measured (they were below the noise level of the detection system). The
same was true at 3 meters distance. However, at 1 meter, signals were
detected.

My first thought is how certain are the 1 meter data? That is, were all
measurements well above (maybe 6 dB) the noise level at 1 meter? However,
let's assume this is true. Since nothing was observed at 3 meters, it's
obvious that the field decay is greater than 6 dB over the 1 to 3 meter
distance.

It would greatly reinforce your claim of an accurate extrapolation algorithm
if you had some empirical data to back up your scheme. For instance, could
you show (and plot) the decay of the strongest emission, over the range of
maybe ½ meter to 3 meters, at ½ meter increments? Once you have some field
decay data, you could then try a regression to a formula for predicting
decay.

Since your emissions are likely not originating in a precisely defined
antenna, the entire physical structure of your EUT is the antenna. Whatever
extrapolation model you come up with will likely not be usable with other
EUT's, but it will probably be better than just assuming 1/(r^2) or 1/(r^3).

I believe that the White EMC Handbook series had a formula for extrapolating
from very near fields to far fields. The decay in the very near field was
1/(r^3), rolling off to 1/(r^2) as the wavelength decreased. The critical
parameters were the distance to the EUT at the close distance, the
wavelength of the emission and the distance to the EUT at the extrapolated
distance. Perhaps this model is discussed in more modern EMC texts also.

Ed Price
WB6WSN
Chula Vista, CA USA

-Original Message-
From: ce-test, qualified testing bv - Gert Gremmen
[mailto:g.grem...@cetest.nl]
Sent: Monday, December 05, 2016 10:46 PM
To: mailto:EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] EN 302 195 Distance Conversion Factor

In the close field area E-field/H-field varies with

Re: [PSES] EN 302 195 Distance Conversion Factor

[Ralph McDiarmid]

I've kept the 6 volume set of the EMC Handbook, by Donald White Consultants, 
for many years.   It's a good reference.

Some standards tell you what to do for correction at different measurements 
distances.  If 3 metres still showed no signal, I'd use amplification and then 
carefully check for overloading.  (esp if at an OATs or in situ)


Ralph McDiarmid
Product Compliance
Engineering
Solar Business
Schneider Electric



From: Ken Javor [mailto:ken.ja...@emccompliance.com]
Sent: Wednesday, December 07, 2016 9:03 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] EN 302 195 Distance Conversion Factor

Re Don White. That math was for an electrically short dipole: short relative to 
wavelength, and short relative to the separation between it and the point of 
observation. Neither of these criteria are obtained at one meter, and therefore 
the math is not useful.

What I just said is what Gert said earlier, much more elegantly.  And English 
is my first language...

Ken Javor
Phone: (256) 650-5261


From: Ed Price <mailto:edpr...@cox.net>
Reply-To: Ed Price <mailto:edpr...@cox.net>
Date: Tue, 6 Dec 2016 05:56:12 -0800
To: <mailto:EMC-PSTC@LISTSERV.IEEE.ORG>
Subject: Re: [PSES] EN 302 195 Distance Conversion Factor

As Gert points out, extrapolation is fraught with hazards of assumptions. If 
you absolutely must attempt to extrapolate data from extreme distances, like a 
1-meter measurement to a 10-meter equivalent field, you should test the sanity 
of your extrapolation algorithm.

For instance, it has been said that, at 10 meters, the emissions could not be 
measured (they were below the noise level of the detection system). The same 
was true at 3 meters distance. However, at 1 meter, signals were detected.

My first thought is how certain are the 1 meter data? That is, were all 
measurements well above (maybe 6 dB) the noise level at 1 meter? However, let's 
assume this is true. Since nothing was observed at 3 meters, it's obvious that 
the field decay is greater than 6 dB over the 1 to 3 meter distance.

It would greatly reinforce your claim of an accurate extrapolation algorithm if 
you had some empirical data to back up your scheme. For instance, could you 
show (and plot) the decay of the strongest emission, over the range of maybe ½ 
meter to 3 meters, at ½ meter increments? Once you have some field decay data, 
you could then try a regression to a formula for predicting decay.

Since your emissions are likely not originating in a precisely defined antenna, 
the entire physical structure of your EUT is the antenna. Whatever 
extrapolation model you come up with will likely not be usable with other 
EUT's, but it will probably be better than just assuming 1/(r^2) or 1/(r^3).

I believe that the White EMC Handbook series had a formula for extrapolating 
from very near fields to far fields. The decay in the very near field was 
1/(r^3), rolling off to 1/(r^2) as the wavelength decreased. The critical 
parameters were the distance to the EUT at the close distance, the wavelength 
of the emission and the distance to the EUT at the extrapolated distance. 
Perhaps this model is discussed in more modern EMC texts also.

Ed Price
WB6WSN
Chula Vista, CA USA

-Original Message-
From: ce-test, qualified testing bv - Gert Gremmen [mailto:g.grem...@cetest.nl]
Sent: Monday, December 05, 2016 10:46 PM
To: mailto:EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] EN 302 195 Distance Conversion Factor

In the close field area E-field/H-field varies with 1/(r^2) OR 1/(^3) depending 
on the source and nature of it. In addition at close distances similar fields 
may have an opposite vector polarity (close to EUT) and may partially cancel 
each other.
In general it is not a good idea measuring close field components to draw 
conclusions on radiated emission components at greater distances, as these 
components do not actually radiate.
That is why you won't find any conversion factors for frequencies below 30 MHz, 
at distances shorter than the close-far field transition zone. (lambda/2pi)

Of course measurements in this area make sense about the EMI-level  at the 
measurement point, and that is why some standards make measurements in the 
close field at a predefined distance.
Changing that distance will make measurements incomparable.



Regards,

Ing. Gert Gremmen
Approvals manager




-

 This message was scanned by Exchange Online Protection Services.


-

This message is from the IEEE Product Safety Engineering Society emc-pstc 
discussion list. To post a message to the list, send your e-mail to 
<emc-p...@ieee.org>

All emc-pstc postings are archived and searchable on the web at:
http://www.ieee-pses.org/emc-pstc.html

Attachments are no

Re: [PSES] EN 302 195 Distance Conversion Factor

[Ken Javor]

Re Don White. That math was for an electrically short dipole: short relative
to wavelength, and short relative to the separation between it and the point
of observation. Neither of these criteria are obtained at one meter, and
therefore the math is not useful.

What I just said is what Gert said earlier, much more elegantly.  And
English is my first language...

Ken Javor
Phone: (256) 650-5261



From: Ed Price <edpr...@cox.net>
Reply-To: Ed Price <edpr...@cox.net>
Date: Tue, 6 Dec 2016 05:56:12 -0800
To: <EMC-PSTC@LISTSERV.IEEE.ORG>
Subject: Re: [PSES] EN 302 195 Distance Conversion Factor

As Gert points out, extrapolation is fraught with hazards of assumptions. If
you absolutely must attempt to extrapolate data from extreme distances, like
a 1-meter measurement to a 10-meter equivalent field, you should test the
sanity of your extrapolation algorithm.
 
For instance, it has been said that, at 10 meters, the emissions could not
be measured (they were below the noise level of the detection system). The
same was true at 3 meters distance. However, at 1 meter, signals were
detected.
 
My first thought is how certain are the 1 meter data? That is, were all
measurements well above (maybe 6 dB) the noise level at 1 meter? However,
let¹s assume this is true. Since nothing was observed at 3 meters, it¹s
obvious that the field decay is greater than 6 dB over the 1 to 3 meter
distance.
 
It would greatly reinforce your claim of an accurate extrapolation algorithm
if you had some empirical data to back up your scheme. For instance, could
you show (and plot) the decay of the strongest emission, over the range of
maybe 1Ž2 meter to 3 meters, at 1Ž2 meter increments? Once you have some field
decay data, you could then try a regression to a formula for predicting
decay.
 
Since your emissions are likely not originating in a precisely defined
antenna, the entire physical structure of your EUT is the antenna. Whatever
extrapolation model you come up with will likely not be usable with other
EUT¹s, but it will probably be better than just assuming 1/(r^2) or 1/(r^3).
 
I believe that the White EMC Handbook series had a formula for extrapolating
from very near fields to far fields. The decay in the very near field was
1/(r^3), rolling off to 1/(r^2) as the wavelength decreased. The critical
parameters were the distance to the EUT at the close distance, the
wavelength of the emission and the distance to the EUT at the extrapolated
distance. Perhaps this model is discussed in more modern EMC texts also.
 
Ed Price
WB6WSN
Chula Vista, CA USA
 
-Original Message-
From: ce-test, qualified testing bv - Gert Gremmen
[mailto:g.grem...@cetest.nl]
Sent: Monday, December 05, 2016 10:46 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] EN 302 195 Distance Conversion Factor
 
In the close field area E-field/H-field varies with 1/(r^2) OR 1/(^3)
depending on the source and nature of it. In addition at close distances
similar fields may have an opposite vector polarity (close to EUT) and may
partially cancel each other.
In general it is not a good idea measuring close field components to draw
conclusions on radiated emission components at greater distances, as these
components do not actually radiate.
That is why you won¹t find any conversion factors for frequencies below 30
MHz, at distances shorter than the close-far field transition zone.
(lambda/2pi)
 
Of course measurements in this area make sense about the EMI-level  at the
measurement point, and that is why some standards make measurements in the
close field at a predefined distance.
Changing that distance will make measurements incomparable.
 
 
 
Regards,
 
Ing. Gert Gremmen
Approvals manager


 
 
+ ce marking of electrical/electronic equipment Independent Consultancy
+ Services Compliance Testing and Design for CE marking according to
+ EC-directives:
  - Electro Magnetic Compatibility 2014/30/EC
- Electrical Safety 2014/35/EC
- Radio & Telecommunication Terminal Equipment 99/5/EC
 
Web:    www.cetest.nl <http://www.cetest.nl>   (English) www.ce-test.nl
<http://www.ce-test.nl>  (Dutch) www.cetest.fr <http://www.cetest.fr>
(under construction)
Phone :  +31 10 415 24 26
---
This e-mail and any attachments thereto may contain information that is
confidential and/or protected by intellectual property rights and are
intended for the sole use of the recipient(s) named above.
Any use of the information contained herein (including, but not limited to,
total or partial reproduction, communication or distribution in any form) by
persons other than the designated
recipient(s) is prohibited. If you have received this e-mail in error,
please notify the sender either by telephone or by e-mail and delete the
material from any computer.
Thank you for your co-operation.
 
From: Grace Lin [mai

Re: [PSES] EN 302 195 Distance Conversion Factor

[Ed Price]

As Gert points out, extrapolation is fraught with hazards of assumptions. If 
you absolutely must attempt to extrapolate data from extreme distances, like a 
1-meter measurement to a 10-meter equivalent field, you should test the sanity 
of your extrapolation algorithm.

 

For instance, it has been said that, at 10 meters, the emissions could not be 
measured (they were below the noise level of the detection system). The same 
was true at 3 meters distance. However, at 1 meter, signals were detected.

 

My first thought is how certain are the 1 meter data? That is, were all 
measurements well above (maybe 6 dB) the noise level at 1 meter? However, let’s 
assume this is true. Since nothing was observed at 3 meters, it’s obvious that 
the field decay is greater than 6 dB over the 1 to 3 meter distance.

 

It would greatly reinforce your claim of an accurate extrapolation algorithm if 
you had some empirical data to back up your scheme. For instance, could you 
show (and plot) the decay of the strongest emission, over the range of maybe ½ 
meter to 3 meters, at ½ meter increments? Once you have some field decay data, 
you could then try a regression to a formula for predicting decay.

 

Since your emissions are likely not originating in a precisely defined antenna, 
the entire physical structure of your EUT is the antenna. Whatever 
extrapolation model you come up with will likely not be usable with other 
EUT’s, but it will probably be better than just assuming 1/(r^2) or 1/(r^3).

 

I believe that the White EMC Handbook series had a formula for extrapolating 
from very near fields to far fields. The decay in the very near field was 
1/(r^3), rolling off to 1/(r^2) as the wavelength decreased. The critical 
parameters were the distance to the EUT at the close distance, the wavelength 
of the emission and the distance to the EUT at the extrapolated distance. 
Perhaps this model is discussed in more modern EMC texts also.

 

Ed Price
WB6WSN
Chula Vista, CA USA

 

-Original Message-
From: ce-test, qualified testing bv - Gert Gremmen [mailto:g.grem...@cetest.nl] 
Sent: Monday, December 05, 2016 10:46 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] EN 302 195 Distance Conversion Factor

 

In the close field area E-field/H-field varies with 1/(r^2) OR 1/(^3) depending 
on the source and nature of it. In addition at close distances similar fields 
may have an opposite vector polarity (close to EUT) and may partially cancel 
each other. 

In general it is not a good idea measuring close field components to draw 
conclusions on radiated emission components at greater distances, as these 
components do not actually radiate.

That is why you won’t find any conversion factors for frequencies below 30 MHz, 
at distances shorter than the close-far field transition zone. (lambda/2pi)

 

Of course measurements in this area make sense about the EMI-level  at the 
measurement point, and that is why some standards make measurements in the 
close field at a predefined distance.

Changing that distance will make measurements incomparable.

 

 

Regards,

 

Ing. Gert Gremmen

Approvals manager



 

 

+ ce marking of electrical/electronic equipment Independent Consultancy 

+ Services Compliance Testing and Design for CE marking according to 

+ EC-directives:

  - Electro Magnetic Compatibility 2014/30/EC

- Electrical Safety 2014/35/EC

- Radio & Telecommunication Terminal Equipment 99/5/EC

 

Web: <http://www.cetest.nl> www.cetest.nl  (English)  
<http://www.ce-test.nl> www.ce-test.nl (Dutch)  <http://www.cetest.fr> 
www.cetest.fr (under construction)

Phone :  +31 10 415 24 26

---

This e-mail and any attachments thereto may contain information that is 
confidential and/or protected by intellectual property rights and are intended 
for the sole use of the recipient(s) named above. 

Any use of the information contained herein (including, but not limited to, 
total or partial reproduction, communication or distribution in any form) by 
persons other than the designated

recipient(s) is prohibited. If you have received this e-mail in error, please 
notify the sender either by telephone or by e-mail and delete the material from 
any computer. 

Thank you for your co-operation.

 

From: Grace Lin [ <mailto:graceli...@gmail.com> mailto:graceli...@gmail.com]

Sent: Tuesday 6 December 2016 00:46

To:  <mailto:EMC-PSTC@LISTSERV.IEEE.ORG> EMC-PSTC@LISTSERV.IEEE.ORG

Subject: [PSES] EN 302 195 Distance Conversion Factor

 

Dear Members,

 

What is the appropriate distance conversion factor per EN 302 195, 9 kHz - 30 
MHz?  The limits were specified at 10m.  Test data was too low to be detected 
at 10m and 3m.  1m distance was used to collect some data.

 

EN 300 330 provides a chart for the distance conversion fact

Re: [PSES] EN 302 195 Distance Conversion Factor

[ce-test, qualified testing bv - Gert Gremmen]

In the close field area E-field/H-field varies with 1/(r^2) OR 1/(^3) depending 
on the source
and nature of it. In addition at close distances similar fields may have an 
opposite
vector polarity (close to EUT) and may partially cancel each other. 
In general it is not a good idea measuring close field components to draw 
conclusions
on radiated emission components at greater distances, as these components do 
not 
actually radiate.
That is why you won’t find any conversion factors for frequencies below 30 MHz,
at distances shorter than the close-far field transition zone. (lambda/2pi)

Of course measurements in this area make sense about the EMI-level  at the 
measurement point,
and that is why some standards make measurements in the close field at a 
predefined distance.
Changing that distance will make measurements incomparable.


 
Regards,

Ing. Gert Gremmen
Approvals manager



+ ce marking of electrical/electronic equipment
+ Independent Consultancy Services
+ Compliance Testing and Design for CE marking according to EC-directives:
  - Electro Magnetic Compatibility 2014/30/EC
- Electrical Safety 2014/35/EC
- Radio & Telecommunication Terminal Equipment 99/5/EC

Web:    www.cetest.nl  (English) www.ce-test.nl (Dutch) www.cetest.fr (under 
construction)
Phone :  +31 10 415 24 26
---
This e-mail and any attachments thereto may contain information 
that is confidential and/or protected by intellectual property rights 
and are intended for the sole use of the recipient(s) named above. 
Any use of the information contained herein (including, but not 
limited to, total or partial reproduction, communication or 
distribution in any form) by persons other than the designated 
recipient(s) is prohibited. If you have received this e-mail in error, 
please notify the sender either by telephone or by e-mail and 
delete the material from any computer. 
Thank you for your co-operation.

From: Grace Lin [mailto:graceli...@gmail.com] 
Sent: Tuesday 6 December 2016 00:46
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: [PSES] EN 302 195 Distance Conversion Factor

Dear Members,

What is the appropriate distance conversion factor per EN 302 195, 9 kHz - 30 
MHz?  The limits were specified at 10m.  Test data was too low to be detected 
at 10m and 3m.  1m distance was used to collect some data.

EN 300 330 provides a chart for the distance conversion factors between 3m and 
10m.  It seems there is no such information in EN 302 195.

Thank you very much for your time and I look forward to hearing from you.

Best regards,
Grace Lin
-

This message is from the IEEE Product Safety Engineering Society emc-pstc 
discussion list. To post a message to the list, send your e-mail to 

All emc-pstc postings are archived and searchable on the web at: 
http://www.ieee-pses.org/emc-pstc.html
Attachments are not permitted but the IEEE PSES Online Communities site at 
http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used 
formats), large files, etc.
Website: http://www.ieee-pses.org/
Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe)
List rules: http://www.ieee-pses.org/listrules.html 
For help, send mail to the list administrators:
Scott Douglas 
Mike Cantwell  
For policy questions, send mail to:
Jim Bacher 
David Heald  

-

This message is from the IEEE Product Safety Engineering Society emc-pstc 
discussion list. To post a message to the list, send your e-mail to 


All emc-pstc postings are archived and searchable on the web at:
http://www.ieee-pses.org/emc-pstc.html

Attachments are not permitted but the IEEE PSES Online Communities site at 
http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used 
formats), large files, etc.

Website:  http://www.ieee-pses.org/
Instructions:  http://www.ieee-pses.org/list.html (including how to unsubscribe)
List rules: http://www.ieee-pses.org/listrules.html

For help, send mail to the list administrators:
Scott Douglas 
Mike Cantwell 

For policy questions, send mail to:
Jim Bacher:  
David Heald: 

Re: [PSES] EN 302 195 Distance Conversion Factor

[John Woodgate]

In the absence of any other solution, you could use the 300 330 factor and 
explain why In an 'EMC assessment document'.
 
With best wishes DESIGN IT IN! OOO – Own Opinions Only
  www.jmwa.demon.co.uk J M Woodgate and 
Associates Rayleigh England
 
Sylvae in aeternum manent.
 
From: Grace Lin [mailto:graceli...@gmail.com] 
Sent: Monday, December 5, 2016 11:46 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: [PSES] EN 302 195 Distance Conversion Factor
 
Dear Members,
 
What is the appropriate distance conversion factor per EN 302 195, 9 kHz - 30 
MHz?  The limits were specified at 10m.  Test data was too low to be detected 
at 10m and 3m.  1m distance was used to collect some data.
 
EN 300 330 provides a chart for the distance conversion factors between 3m and 
10m.  It seems there is no such information in EN 302 195.
 
Thank you very much for your time and I look forward to hearing from you.
 
Best regards,
Grace Lin
-

This message is from the IEEE Product Safety Engineering Society emc-pstc 
discussion list. To post a message to the list, send your e-mail to 
 >
All emc-pstc postings are archived and searchable on the web at: 
http://www.ieee-pses.org/emc-pstc.html
Attachments are not permitted but the IEEE PSES Online Communities site at 
http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used 
formats), large files, etc.
Website: http://www.ieee-pses.org/
Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) 
 
List rules: http://www.ieee-pses.org/listrules.html 
For help, send mail to the list administrators:
Scott Douglas  >
Mike Cantwell  > 
For policy questions, send mail to:
Jim Bacher  >
David Heald  > 

-

This message is from the IEEE Product Safety Engineering Society emc-pstc 
discussion list. To post a message to the list, send your e-mail to 


All emc-pstc postings are archived and searchable on the web at:
http://www.ieee-pses.org/emc-pstc.html

Attachments are not permitted but the IEEE PSES Online Communities site at 
http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used 
formats), large files, etc.

Website:  http://www.ieee-pses.org/
Instructions:  http://www.ieee-pses.org/list.html (including how to unsubscribe)
List rules: http://www.ieee-pses.org/listrules.html

For help, send mail to the list administrators:
Scott Douglas 
Mike Cantwell 

For policy questions, send mail to:
Jim Bacher:  
David Heald: