Re: [PSES] Field probe calibration

[Ken Javor]

It is clear that any correction table built into the field probe
hardware/firmware/software is time domain only, so linearity correction
factors based on amplitude, not frequency domain, because there is no
frequency information unless you are looking at an entirely different kind
of device designed to drive a spectrum analyzer.  With that sort of system
(suppliers of which I am aware include Rohde & Schwarz and Narda), it is
possible to correct in in the frequency domain, but again not a single
standard out there is based on the use of such, as they are quite recent
developments.

Ken Javor
Phone: (256) 650-5261



From: Edward Price 
Reply-To: Edward Price 
Date: Tue, 6 Mar 2018 01:27:07 +
To: 
Conversation: [PSES] Field probe calibration
Subject: Re: [PSES] Field probe calibration

This is interesting, as Mr. Chen stated in ³Practical Considerations on EMC
Measurements using Field Probes² that:
 
³Modern probes have correction table built into the probe. Microcontrollers
inside the probes apply linearity correction. As a result, probe reading
reflects the true field value for CW signals. A user need not to correct for
this manually.²
 
http://ieee.rackoneup.net/rrvs/10/Zhong%20Probe.pdf
 
I believe Mr. Chen was referring to the Lindgren HI-6005 probe in this
example. It wasn¹t clear to me if he meant that the probe had an internal
correction table for the frequency domain, the amplitude domain or both.
 
I would think that isotropicity would have to be proven, not claimed,
through actual measurements at time of calibration. These probes are
operating at frequencies where even a block of Delrin can distort an
E-field. In that document, Mr. Chen presents data for the HI-6005 which
shows a +/- 1Ž4 dB variation in isotropicity (at 400 MHz & 1 GHz, but what
about 6 GHz); that¹s very impressive. I wonder if the probe¹s internal
microprocessor applies any correction factor to smooth the isotropicity?
 
The amplitude and frequency linearity must also be measured, because even
tiny variations in construction of the probes and electronics can cause
resonances or couplings.
 
·   There once was a time when we just measured whatever came out of the
manufacturer¹s antenna.

·   Then we believed that all of the manufacturer¹s antennas had the
same factory response.

·   Then we required calibration data for each antenna.

·   Then we realized that antennas can change, so periodic calibration
became a must.

·   And then we realized that calibrations needed to be done
³end-to-end² starting with a uniform applied RF field.

·   And now we realize that ³several points per octave² is not good
enough resolution.

·   And now that we have microprocessors plucking fudge factors off an
inaccessible table, we have yet another layer on this data onion, and we
have to know what it does to our raw data.

 
Ed Price
WB6WSN
Chula Vista, CA USA
 
From: Patrick [mailto:conwa...@gmail.com]
Sent: Monday, March 05, 2018 1:36 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] Field probe calibration
 

A great presentation on field probes can be found on the web.

The author is Zhong Chen, an engineer with one of the probe manufacturers.

I was lucky enough last year to be in the audience for a live presentation
of this at our local EMC Chapter.

 

I found it by searching:  "ets lindgren e field probe theory"

 

It states, among other things, that frequency response correction is applied
during end use!

 

Unfortunately, it doesn't state the amount of correction needed, nor the
frequency resolution needed (doh!).

But, it does answer questions on whether modern probes are frequency
dependent devices.

 

It is an interesting presentation, and I highly recommend it for anyone that
wants to learn more about their test equipment.

 

 
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Re: [PSES] The Spoofee

[Ghery Pettit]

I got the same statement on an email I sent to the IEEE EMC Society's SDCom
list.  I forwarded it to the chair of the committee and he is checking with
IEEE.  I think their tool needs tweaking.

 

Ghery S. Pettit

 

From: Edward Price [mailto:e...@jwjelp.com] 
Sent: Monday, March 5, 2018 5:42 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: [PSES] The Spoofee

 

Hi Listmembers:

 

Recently, all of my list posts have been prefaced with this courteous little
warning:

 

This sender failed our fraud detection checks and may not be who they appear
to be. 

 

Does everyone receive this warning, or is it just on the copy distributed to
me? My IT Manager (my grandson) says that this could happen if the IEEE
doesn't have the most recent security certificates applied to their mail
server.

 

Please reply off-list if you have a comment, as 700 "yes" or "no" answers
would probably damage today's S/N ratio.

 

Ed Price
WB6WSN
Chula Vista, CA USA

 

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 >

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[PSES] The Spoofee

[Edward Price]

Hi Listmembers:

Recently, all of my list posts have been prefaced with this courteous little 
warning:

This sender failed our fraud detection checks and may not be who they appear to 
be.

Does everyone receive this warning, or is it just on the copy distributed to 
me? My IT Manager (my grandson) says that this could happen if the IEEE doesn't 
have the most recent security certificates applied to their mail server.

Please reply off-list if you have a comment, as 700 "yes" or "no" answers would 
probably damage today's S/N ratio.

Ed Price
WB6WSN
Chula Vista, CA USA


-

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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)
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Mike Cantwell 

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Jim Bacher:  
David Heald: 

Re: [PSES] Field probe calibration

[Edward Price]

This is interesting, as Mr. Chen stated in “Practical Considerations on EMC 
Measurements using Field Probes” that:

“Modern probes have correction table built into the probe. Microcontrollers 
inside the probes apply linearity correction. As a result, probe reading 
reflects the true field value for CW signals. A user need not to correct for 
this manually.”

http://ieee.rackoneup.net/rrvs/10/Zhong%20Probe.pdf

I believe Mr. Chen was referring to the Lindgren HI-6005 probe in this example. 
It wasn’t clear to me if he meant that the probe had an internal correction 
table for the frequency domain, the amplitude domain or both.

I would think that isotropicity would have to be proven, not claimed, through 
actual measurements at time of calibration. These probes are operating at 
frequencies where even a block of Delrin can distort an E-field. In that 
document, Mr. Chen presents data for the HI-6005 which shows a +/- ¼ dB 
variation in isotropicity (at 400 MHz & 1 GHz, but what about 6 GHz); that’s 
very impressive. I wonder if the probe’s internal microprocessor applies any 
correction factor to smooth the isotropicity?

The amplitude and frequency linearity must also be measured, because even tiny 
variations in construction of the probes and electronics can cause resonances 
or couplings.


·There once was a time when we just measured whatever came out of the 
manufacturer’s antenna.

·Then we believed that all of the manufacturer’s antennas had the same 
factory response.

·Then we required calibration data for each antenna.

·Then we realized that antennas can change, so periodic calibration 
became a must.

·And then we realized that calibrations needed to be done “end-to-end” 
starting with a uniform applied RF field.

·And now we realize that “several points per octave” is not good enough 
resolution.

·And now that we have microprocessors plucking fudge factors off an 
inaccessible table, we have yet another layer on this data onion, and we have 
to know what it does to our raw data.

Ed Price
WB6WSN
Chula Vista, CA USA

From: Patrick [mailto:conwa...@gmail.com]
Sent: Monday, March 05, 2018 1:36 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] Field probe calibration

A great presentation on field probes can be found on the web.
The author is Zhong Chen, an engineer with one of the probe manufacturers.
I was lucky enough last year to be in the audience for a live presentation of 
this at our local EMC Chapter.

I found it by searching:  "ets lindgren e field probe theory"

It states, among other things, that frequency response correction is applied 
during end use!

Unfortunately, it doesn't state the amount of correction needed, nor the 
frequency resolution needed (doh!).
But, it does answer questions on whether modern probes are frequency dependent 
devices.

It is an interesting presentation, and I highly recommend it for anyone that 
wants to learn more about their test equipment.



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formats), large files, etc.

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Re: [PSES] Field probe calibration

[Ken Javor]

Thanks for the slide package but have to disagree. The last few slides are
about frequency effects due to probe placement, not inherent in the probe
itself. There is no way to correct for effects due to probe placement. The
frequency correction they talk about in the last slide is how linearity is
affected vs. frequency and that is a very minor correction.  And note this
final phrase:

³Frequency response correction is applied during end use.²

That means it has to be done outside the probe electronics, because the
probe electronics doesn¹t know what the frequency is.  Not saying you can¹t
do this, just it isn¹t required and was never envisioned in any of these
standards, and the degree of the error is so much smaller than other error
sources that it isn¹t worth it.

I am not familiar with modern EMI software control packages. Do any of them
make proviso for this?

Ken Javor
Phone: (256) 650-5261



From: Patrick 
Date: Mon, 5 Mar 2018 15:26:03 -0700
To: Ken Javor 
Cc: 
Subject: Re: [PSES] Field probe calibration

http://ieee.rackoneup.net/rrvs/10/Zhong%20Probe.pdf

Look at the last slide, the last bullet.

The detail analysis can be found within the slides themselves, but that last
bullet summarizes the point.

On Mon, Mar 5, 2018 at 3:10 PM, Ken Javor 
wrote:
> Didn¹t find cited article but did find published ETS/Lindgren specs on a
> laser-powered sensor, showing frequency-dependent performance well within +/-
> 1 dB tolerance over entire specified frequency range below 1 GHz.  Also, no
> standard out there requires the level-of-effort to post-process the field
> sensor electronics unit output on a frequency-by-frequency basis.
> 
> 
> http://www.ets-lindgren.com/sites/etsauthor/ProductsManuals/Probes_Monitors/EM
> C%20Field%20Probes%20399395%20A.pdf
> 
> Page 55.
> 
> Also found:  ³Practical Considerations for Radiated Immunities Measurement
> using ETS-Lindgren EMC Probes,² with nothing about frequency dependence
> corrections.
> 
> Ken Javor
> Phone: (256) 650-5261 
> 
> 
> 
> 
> From: Patrick 
> Date: Mon, 5 Mar 2018 14:36:11 -0700
> To: Ken Javor 
> Cc: 
> Subject: Re: [PSES] Field probe calibration
> 
> A great presentation on field probes can be found on the web.
> The author is Zhong Chen, an engineer with one of the probe manufacturers. 
> I was lucky enough last year to be in the audience for a live presentation of
> this at our local EMC Chapter.
> 
> I found it by searching:  "ets lindgren e field probe theory"  
> 
> It states, among other things, that frequency response correction is applied
> during end use!
> 
> Unfortunately, it doesn't state the amount of correction needed, nor the
> frequency resolution needed (doh!).
> But, it does answer questions on whether modern probes are frequency dependent
> devices.
> 
> It is an interesting presentation, and I highly recommend it for anyone that
> wants to learn more about their test equipment.
> 
> 
> On Mon, Mar 5, 2018 at 1:08 PM, Ken Javor  wrote:
>> In turn:
>> 
>> Everyone does not know that MIL-STD-461 requires RS103 pre-test
>> verification.  I don¹t.  Please explain further.
>> 
>> RTCA/DO-160 requires pre-calibration of the field in a manner similar to that
>> in the exercise that started this thread. Note at one point only, so that the
>> point about field variations down the length of the test set-up as for RS103
>> also applies here.
>> 
>> My use of the 61000-4-3 example was a pedagogical tool to illustrate that the
>> OP test results looked good relative to a very stringent industry standard.
>> 
>> When you ask whether some tolerance is insignificant, that begs the question
>> as to what is the required tolerance.  In MIL-STD-461, the effect of the
>> ground plane and immediate vicinity of the test sample and the lack of good
>> quality absorption below around 80 MHz are way bigger factors than
>> non-idealities in probe calibration.   MIL-STD-461 requires only one probe
>> (more are allowed) so that even if the field intensity is within the correct
>> tolerance at that point, there is no control over what the fields are down
>> the length and breadth of the test set-up.  And MIL-STD-461 allows for 3 dB
>> variation in instrumentation tolerances, so there you go on your field
>> probes.
>> 
>> And I don¹t know what all sorts of control software is envisioned out there,
>> but an off-the-shelf field probe and control-display unit at least at the
>> time when RS103 was written (1989-1993) was not a frequency sensitive device.
>> The unit reported a field intensity only. The frequency information came from
>> the transmit side.  Leveling was performed on the field intensity reported by
>> the probe electronics unit.  There was no correction envisioned for probe
>> factors at each tuned frequency.  

Re: [PSES] IEC60950-1 Limited Power Source via IC current limiter

[Adam Dixon]

This question has been asked on TI's E2E forum for other parts in this family.  
See the 2nd 60950 report link that Eric posted in this discussion thread:
https://e2e.ti.com/support/interface/usb/f/1008/t/563031

It might be worth opening a new thread for this particular part number to see 
if there is another IEC 60950 report that TI would share.  Or maybe this report 
would suffice.


Cheers,
Adam in Atlanta
adam.di...@ieee.org

Sent from my iPad

> On Mar 5, 2018, at 4:42 PM, Ted Eckert 
> <07cf6ebeab9d-dmarc-requ...@ieee.org> wrote:
> 
> I agree with Mr. Woodgate and I can add a little more information. UL 2367 is 
> generally considered equivalent as Test Program 2 of Annex CC. Most NCBs will 
> accept it as such and you should be able to place a statement in your report 
> indicating the equivalency. Not all NCBs will necessarily accept the 
> equivalence, but I have yet to run into an issue with integrated circuits 
> approved under UL 2367.
>  
> Ted Eckert
> Microsoft Corporation
>  
> The opinions expressed are my own and do not necessarily reflect those of my 
> employer.
>  
> From: John Woodgate  
> Sent: Monday, March 5, 2018 1:07 PM
> To: EMC-PSTC@LISTSERV.IEEE.ORG
> Subject: Re: [PSES] IEC60950-1 Limited Power Source via IC current limiter
>  
> The standard says '...meets a suitable test program as given in Annex CC' 
> [not Annex C].  It does not say 'shall meet the test program given in Annex 
> CC'. As you know, the manufacturer is permitted  to decide (and document) 
> that a part meeting UL2367 is acceptable, and it would be up to a regulatory 
> authority to challenge that. It seems unlikely that UL 2367 would be 
> deficient, since this is a precaution against fire, which is a major concern 
> of UL, of course.
> 
> John Woodgate OOO-Own Opinions Only
> J M Woodgate and Associates www.woodjohn.uk
> Rayleigh, Essex UK
> On 2018-03-05 20:11, Charlie Blackham wrote:
> All
>  
> Client has designed a USB port with the DC power protected by a TI TPS2052B 
> Current limiter:
> Component details: www.ti.com/product/TPS2052B/description
> Component is UL recognised component under QVGS2.E169910 which is based on UL 
> 2367
>  
>  
> 2.5 Limited power sources
> c) a regulating network, or an integrated circuit (IC) current limiter, 
> limits the output in compliance with Table 2B, both with and without a 
> simulated single fault (see 1.4.14) in the regulating network or the IC 
> current limiter (open circuit or short circuit). A single fault between the 
> input and output is not conducted if the IC current limiter meets a suitable 
> test program as given in Annex CC;
>  
> Annex CC requires appears to require quite extensive testing of the 
> component, and I can’t tell whether a component recognised against UL2367 
> would meet this or not.
>  
> The issue, is that if they s/c the protection component, the output may no 
> longer be LPS – we have provision to fit a suitable fuse on the board, but 
> would prefer not to, so would be grateful for any advice
>  
> Thanks
> Charlie
>  
>  
> Charlie Blackham
> Sulis Consultants Ltd
> Mead House
> Longwater Road
> Eversley
> RG27 0NW
> UK
> Tel: +44 (0)7946 624317
> Email: char...@sulisconsultants.com
> Web: www.sulisconsultants.com
> Registered in England and Wales, number 05466247
>  
> -
> 
> 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.
> 
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>  
> -
> 
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> 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: 
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> http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used 
> formats), large files, etc.
> 
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> unsubscribe)
> List rules: 

Re: [PSES] Field probe calibration

[Patrick]

http://ieee.rackoneup.net/rrvs/10/Zhong%20Probe.pdf

Look at the last slide, the last bullet.

The detail analysis can be found within the slides themselves, but that
last bullet summarizes the point.

On Mon, Mar 5, 2018 at 3:10 PM, Ken Javor 
wrote:

> Didn’t find cited article but did find published ETS/Lindgren specs on a
> laser-powered sensor, showing frequency-dependent performance well within
> +/- 1 dB tolerance over entire specified frequency range below 1 GHz.
> Also, no standard out there requires the level-of-effort to post-process
> the field sensor electronics unit output on a frequency-by-frequency basis.
>
>
> http://www.ets-lindgren.com/sites/etsauthor/ProductsManuals/Probes_
> Monitors/EMC%20Field%20Probes%20399395%20A.pdf
>
> Page 55.
>
> Also found:  “Practical Considerations for Radiated Immunities Measurement
> using ETS-Lindgren EMC Probes,” with nothing about frequency dependence
> corrections.
>
> Ken Javor
> Phone: (256) 650-5261
>
>
>
> --
> *From: *Patrick 
> *Date: *Mon, 5 Mar 2018 14:36:11 -0700
> *To: *Ken Javor 
> *Cc: *
> *Subject: *Re: [PSES] Field probe calibration
>
> A great presentation on field probes can be found on the web.
> The author is Zhong Chen, an engineer with one of the probe manufacturers.
> I was lucky enough last year to be in the audience for a live presentation
> of this at our local EMC Chapter.
>
> I found it by searching:  "ets lindgren e field probe theory"
>
> It states, among other things, that frequency response correction is
> applied during end use!
>
> Unfortunately, it doesn't state the amount of correction needed, nor the
> frequency resolution needed (doh!).
> But, it does answer questions on whether modern probes are frequency
> dependent devices.
>
> It is an interesting presentation, and I highly recommend it for anyone
> that wants to learn more about their test equipment.
>
>
> On Mon, Mar 5, 2018 at 1:08 PM, Ken Javor 
> wrote:
>
> In turn:
>
> Everyone does not know that MIL-STD-461 requires RS103 pre-test
> verification.  I don’t.  Please explain further.
>
> RTCA/DO-160 requires pre-calibration of the field in a manner similar to
> that in the exercise that started this thread. Note at one point only, so
> that the point about field variations down the length of the test set-up as
> for RS103 also applies here.
>
> My use of the 61000-4-3 example was a pedagogical tool to illustrate that
> the OP test results looked good relative to a very stringent industry
> standard.
>
> When you ask whether some tolerance is insignificant, that begs the
> question as to what is the required tolerance.  In MIL-STD-461, the effect
> of the ground plane and immediate vicinity of the test sample and the lack
> of good quality absorption below around 80 MHz are way bigger factors than
> non-idealities in probe calibration.   MIL-STD-461 requires only one probe
> (more are allowed) so that even if the field intensity is within the
> correct tolerance at that point, there is no control over what the fields
> are down the length and breadth of the test set-up.  And MIL-STD-461 allows
> for 3 dB variation in instrumentation tolerances, so there you go on your
> field probes.
>
> And I don’t know what all sorts of control software is envisioned out
> there, but an off-the-shelf field probe and control-display unit at least
> at the time when RS103 was written (1989-1993) was not a frequency
> sensitive device. The unit reported a field intensity only. The frequency
> information came from the transmit side.  Leveling was performed on the
> field intensity reported by the probe electronics unit.  There was no
> correction envisioned for probe factors at each tuned frequency.  Not
> saying that couldn’t be done in a controller external to the probe
> electronics given detailed probe calibration info, just that wasn’t part of
> the plan back in the day. I would be interested to hear from readers as to
> whether that is now common.
>
> As Mr. Woodgate notes and I affirm, a 20% variation in probe calibration
> is way down in the noise even in a 61000-4-3 UFA calibration, not to
> mention the OP set-up with probes 10 cm over a ground plane, which to my
> knowledge is never the requirement.
>
> Which all leads up to an answer to this question:
>
> “Would you agree, as an engineer, its always better to have the data, then
> to operate in the blind?”
>
> The answer is, “Not only no, but hell no, if I know beforehand that the
> numbers don’t matter.”
>
>
> Ken Javor
> Phone: (256) 650-5261 
>
>
> --
> *From: *Patrick 
> *Date: *Mon, 5 Mar 2018 11:10:52 -0700
> *To: *Ken Javor 
> *Cc: *
> *Subject: *Re: [PSES] Field probe calibration
>
> Well, some of us have to consider other 

Re: [PSES] IEC60950-1 Limited Power Source via IC current limiter

[Ted Eckert]

I agree with Mr. Woodgate and I can add a little more information. UL 2367 is 
generally considered equivalent as Test Program 2 of Annex CC. Most NCBs will 
accept it as such and you should be able to place a statement in your report 
indicating the equivalency. Not all NCBs will necessarily accept the 
equivalence, but I have yet to run into an issue with integrated circuits 
approved under UL 2367.

Ted Eckert
Microsoft Corporation

The opinions expressed are my own and do not necessarily reflect those of my 
employer.

From: John Woodgate 
Sent: Monday, March 5, 2018 1:07 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] IEC60950-1 Limited Power Source via IC current limiter


The standard says '...meets a suitable test program as given in Annex CC' [not 
Annex C].  It does not say 'shall meet the test program given in Annex CC'. As 
you know, the manufacturer is permitted  to decide (and document) that a part 
meeting UL2367 is acceptable, and it would be up to a regulatory authority to 
challenge that. It seems unlikely that UL 2367 would be deficient, since this 
is a precaution against fire, which is a major concern of UL, of course.

John Woodgate OOO-Own Opinions Only

J M Woodgate and Associates 
www.woodjohn.uk

Rayleigh, Essex UK
On 2018-03-05 20:11, Charlie Blackham wrote:
All

Client has designed a USB port with the DC power protected by a TI TPS2052B 
Current limiter:

  *   Component details: 
www.ti.com/product/TPS2052B/description
  *   Component is UL recognised component under QVGS2.E169910 which is based 
on UL 2367


2.5 Limited power sources
c) a regulating network, or an integrated circuit (IC) current limiter, limits 
the output in compliance with Table 2B, both with and without a simulated 
single fault (see 1.4.14) in the regulating network or the IC current limiter 
(open circuit or short circuit). A single fault between the input and output is 
not conducted if the IC current limiter meets a suitable test program as given 
in Annex CC;

Annex CC requires appears to require quite extensive testing of the component, 
and I can't tell whether a component recognised against UL2367 would meet this 
or not.

The issue, is that if they s/c the protection component, the output may no 
longer be LPS - we have provision to fit a suitable fuse on the board, but 
would prefer not to, so would be grateful for any advice

Thanks
Charlie


Charlie Blackham
Sulis Consultants Ltd
Mead House
Longwater Road
Eversley
RG27 0NW
UK
Tel: +44 (0)7946 624317
Email: char...@sulisconsultants.com
Web: 
www.sulisconsultants.com
Registered in England and Wales, number 05466247

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

All emc-pstc postings are archived and searchable on the web at: 
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Attachments are not permitted but the IEEE PSES Online Communities site at 

Re: [PSES] Field probe calibration

[Patrick]

A great presentation on field probes can be found on the web.
The author is Zhong Chen, an engineer with one of the probe manufacturers.
I was lucky enough last year to be in the audience for a live presentation
of this at our local EMC Chapter.

I found it by searching:  "ets lindgren e field probe theory"

It states, among other things, that frequency response correction is
applied during end use!

Unfortunately, it doesn't state the amount of correction needed, nor the
frequency resolution needed (doh!).
But, it does answer questions on whether modern probes are frequency
dependent devices.

It is an interesting presentation, and I highly recommend it for anyone
that wants to learn more about their test equipment.


On Mon, Mar 5, 2018 at 1:08 PM, Ken Javor 
wrote:

> In turn:
>
> Everyone does not know that MIL-STD-461 requires RS103 pre-test
> verification.  I don’t.  Please explain further.
>
> RTCA/DO-160 requires pre-calibration of the field in a manner similar to
> that in the exercise that started this thread. Note at one point only, so
> that the point about field variations down the length of the test set-up as
> for RS103 also applies here.
>
> My use of the 61000-4-3 example was a pedagogical tool to illustrate that
> the OP test results looked good relative to a very stringent industry
> standard.
>
> When you ask whether some tolerance is insignificant, that begs the
> question as to what is the required tolerance.  In MIL-STD-461, the effect
> of the ground plane and immediate vicinity of the test sample and the lack
> of good quality absorption below around 80 MHz are way bigger factors than
> non-idealities in probe calibration.   MIL-STD-461 requires only one probe
> (more are allowed) so that even if the field intensity is within the
> correct tolerance at that point, there is no control over what the fields
> are down the length and breadth of the test set-up.  And MIL-STD-461 allows
> for 3 dB variation in instrumentation tolerances, so there you go on your
> field probes.
>
> And I don’t know what all sorts of control software is envisioned out
> there, but an off-the-shelf field probe and control-display unit at least
> at the time when RS103 was written (1989-1993) was not a frequency
> sensitive device. The unit reported a field intensity only. The frequency
> information came from the transmit side.  Leveling was performed on the
> field intensity reported by the probe electronics unit.  There was no
> correction envisioned for probe factors at each tuned frequency.  Not
> saying that couldn’t be done in a controller external to the probe
> electronics given detailed probe calibration info, just that wasn’t part of
> the plan back in the day. I would be interested to hear from readers as to
> whether that is now common.
>
> As Mr. Woodgate notes and I affirm, a 20% variation in probe calibration
> is way down in the noise even in a 61000-4-3 UFA calibration, not to
> mention the OP set-up with probes 10 cm over a ground plane, which to my
> knowledge is never the requirement.
>
> Which all leads up to an answer to this question:
>
> “Would you agree, as an engineer, its always better to have the data, then
> to operate in the blind?”
>
> The answer is, “Not only no, but hell no, if I know beforehand that the
> numbers don’t matter.”
>
>
> Ken Javor
> Phone: (256) 650-5261
>
>
> --
> *From: *Patrick 
> *Date: *Mon, 5 Mar 2018 11:10:52 -0700
> *To: *Ken Javor 
> *Cc: *
> *Subject: *Re: [PSES] Field probe calibration
>
> Well, some of us have to consider other requirements, not just EN's.
>
> What if the test is -461, or DO-160 ?
> And what if the requirement is 200 V/m ?
>
> As everyone knows, those require a pre-test verification, not a
> requirement for "uniform field"?
>
> So a 20% error gives anywhere from 160 V/m to 240 V/m.
> A 600 V/m target is anywhere from 480 V/m to 720 V/m.
>
> Is that insignificant?
> Maybe, maybe not.
> Depends on you and your customer.
>
> I recommend to always check a test labs calibration factors.
> If the factors don't show the resonances, then there are built in errors.
> An informed decision can be made whether to accept, or move to another lab.
>
> Would you agree, as an engineer, its always better to have the data, then
> to operate in the blind?
>
>
> On Mon, Mar 5, 2018 at 10:21 AM, Ken Javor 
> wrote:
>
> I am totally with John Woodgate on this – 20% deltas are insignificant in
> the larger picture. I only used 61000-4-3 to demonstrate the fallacy of
> worrying about such small deviations when the overall requirement in a
> really well-designed and expensive chamber is +6, - 0 dB. Consider the type
> of absorber used, the limited frequency range (80 – 1000 MHz), the total
> lack of conducting material, and the fact that 25% of the UFA may be
> excluded from the 6 dB variation.
>

Re: [PSES] IEC60950-1 Limited Power Source via IC current limiter

[John Woodgate]

The standard says '...meets a suitable test program as given in Annex 
CC' [not Annex C].  It does not say 'shall meet the test program given 
in Annex CC'. As you know, the manufacturer is permitted  to decide (and 
document) that a part meeting UL2367 is acceptable, and it would be up 
to a regulatory authority to challenge that. It seems unlikely that UL 
2367 would be deficient, since this is a precaution against fire, which 
is a major concern of UL, of course.


John Woodgate OOO-Own Opinions Only
J M Woodgate and Associates www.woodjohn.uk
Rayleigh, Essex UK

On 2018-03-05 20:11, Charlie Blackham wrote:


All

Client has designed a USB port with the DC power protected by a TI 
TPS2052B Current limiter:


  * Component details: www.ti.com/product/TPS2052B/description

  * Component is UL recognised component under QVGS2.E169910 which is
based on UL 2367

*2.5 Limited power sources*

c) a regulating network, or an integrated circuit (IC) current 
limiter, limits the output in compliance with Table 2B, both with and 
without a simulated single fault (see 1.4.14) in the regulating 
network or the IC current limiter (open circuit or short circuit). A 
single fault between the input and output is not conducted if the IC 
current limiter meets a suitable test program as given in Annex CC;


Annex CC requires appears to require quite extensive testing of the 
component, and I can’t tell whether a component recognised against 
UL2367 would meet this or not.


The issue, is that if they s/c the protection component, the output 
may no longer be LPS – we have provision to fit a suitable fuse on the 
board, but would prefer not to, so would be grateful for any advice


Thanks

Charlie

*Charlie Blackham*

*Sulis Consultants Ltd*

*Mead House*

*Longwater Road*

*Eversley*

*RG27 0NW*

*UK*

*Tel: +44 (0)7946 624317*

*Email: char...@sulisconsultants.com 
*


*Web: **www.sulisconsultants.com* 



Registered in England and Wales, number 05466247

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-

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

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

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Scott Douglas 
Mike Cantwell 

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

[PSES] IEC60950-1 Limited Power Source via IC current limiter

[Charlie Blackham]

All

Client has designed a USB port with the DC power protected by a TI TPS2052B 
Current limiter:

  *   Component details: 
www.ti.com/product/TPS2052B/description
  *   Component is UL recognised component under QVGS2.E169910 which is based 
on UL 2367


2.5 Limited power sources
c) a regulating network, or an integrated circuit (IC) current limiter, limits 
the output in compliance with Table 2B, both with and without a simulated 
single fault (see 1.4.14) in the regulating network or the IC current limiter 
(open circuit or short circuit). A single fault between the input and output is 
not conducted if the IC current limiter meets a suitable test program as given 
in Annex CC;

Annex CC requires appears to require quite extensive testing of the component, 
and I can't tell whether a component recognised against UL2367 would meet this 
or not.

The issue, is that if they s/c the protection component, the output may no 
longer be LPS - we have provision to fit a suitable fuse on the board, but 
would prefer not to, so would be grateful for any advice

Thanks
Charlie


Charlie Blackham
Sulis Consultants Ltd
Mead House
Longwater Road
Eversley
RG27 0NW
UK
Tel: +44 (0)7946 624317
Email: char...@sulisconsultants.com
Web: 
www.sulisconsultants.com
Registered in England and Wales, number 05466247


-

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] Field probe calibration

[Ken Javor]

In turn:

Everyone does not know that MIL-STD-461 requires RS103 pre-test
verification.  I don¹t.  Please explain further.

RTCA/DO-160 requires pre-calibration of the field in a manner similar to
that in the exercise that started this thread. Note at one point only, so
that the point about field variations down the length of the test set-up as
for RS103 also applies here.

My use of the 61000-4-3 example was a pedagogical tool to illustrate that
the OP test results looked good relative to a very stringent industry
standard.

When you ask whether some tolerance is insignificant, that begs the question
as to what is the required tolerance.  In MIL-STD-461, the effect of the
ground plane and immediate vicinity of the test sample and the lack of good
quality absorption below around 80 MHz are way bigger factors than
non-idealities in probe calibration.   MIL-STD-461 requires only one probe
(more are allowed) so that even if the field intensity is within the correct
tolerance at that point, there is no control over what the fields are down
the length and breadth of the test set-up.  And MIL-STD-461 allows for 3 dB
variation in instrumentation tolerances, so there you go on your field
probes.

And I don¹t know what all sorts of control software is envisioned out there,
but an off-the-shelf field probe and control-display unit at least at the
time when RS103 was written (1989-1993) was not a frequency sensitive
device. The unit reported a field intensity only. The frequency information
came from the transmit side.  Leveling was performed on the field intensity
reported by the probe electronics unit.  There was no correction envisioned
for probe factors at each tuned frequency.  Not saying that couldn¹t be done
in a controller external to the probe electronics given detailed probe
calibration info, just that wasn¹t part of the plan back in the day. I would
be interested to hear from readers as to whether that is now common.

As Mr. Woodgate notes and I affirm, a 20% variation in probe calibration is
way down in the noise even in a 61000-4-3 UFA calibration, not to mention
the OP set-up with probes 10 cm over a ground plane, which to my knowledge
is never the requirement.

Which all leads up to an answer to this question:

³Would you agree, as an engineer, its always better to have the data, then
to operate in the blind?²

The answer is, ³Not only no, but hell no, if I know beforehand that the
numbers don¹t matter.²


Ken Javor
Phone: (256) 650-5261



From: Patrick 
Date: Mon, 5 Mar 2018 11:10:52 -0700
To: Ken Javor 
Cc: 
Subject: Re: [PSES] Field probe calibration

Well, some of us have to consider other requirements, not just EN's.
  
What if the test is -461, or DO-160 ?
And what if the requirement is 200 V/m ?

As everyone knows, those require a pre-test verification, not a requirement
for "uniform field"?

So a 20% error gives anywhere from 160 V/m to 240 V/m.
A 600 V/m target is anywhere from 480 V/m to 720 V/m.

Is that insignificant?
Maybe, maybe not.
Depends on you and your customer.

I recommend to always check a test labs calibration factors.
If the factors don't show the resonances, then there are built in errors.
An informed decision can be made whether to accept, or move to another lab.

Would you agree, as an engineer, its always better to have the data, then to
operate in the blind?


On Mon, Mar 5, 2018 at 10:21 AM, Ken Javor 
wrote:
> I am totally with John Woodgate on this ­ 20% deltas are insignificant in the
> larger picture. I only used 61000-4-3 to demonstrate the fallacy of worrying
> about such small deviations when the overall requirement in a really
> well-designed and expensive chamber is +6, - 0 dB. Consider the type of
> absorber used, the limited frequency range (80 ­ 1000 MHz), the total lack of
> conducting material, and the fact that 25% of the UFA may be excluded from the
> 6 dB variation.  
> 
> Your variations are well within that tolerance, and your room and set-up
> nowhere near that good.  If you want better than what you have, you will need
> a chamber and set-up much better than that for 61000-4-3 ­ impractical, to say
> the least.
> 
> The point is, make sure you have enough amplifier to do the job with some
> margin. That¹s as good as you are going to get.
> 
> Ken Javor
> Phone: (256) 650-5261 
> 
> 
> 
> From: John Woodgate 
> Reply-To: John Woodgate 
> Date: Mon, 5 Mar 2018 16:19:10 +
> To: 
> Subject: Re: [PSES] Field probe calibration
> 
>    
> 
> +/- 20% doesn't seem to be enough to explain the reported result. After all,
> assuming the +/- 20% is off the spectrum analyser, 1.2 is +1.6 dB and 0.8 is
> -1.9 dB. These are small, but not negligible. If the +/-20% relates to power,
> they are even smaller in dB, of course.
>  
>  
> John Woodgate OOO-Own Opinions Only
> J M 

Re: [PSES] Field probe calibration

[John Woodgate]

You can't 'solve' it. You always get the effects you are concerned about 
when you try to measure field strengths in the near field. If you had 
access to a multiphysics field plotting suite, you would see in vivid 
colour how the field strength varies vastly in strengthand direction in 
some places but less in others. You can get a rough idea by looking at 
one of those pictures of the field of a bar magnet disclosed by iron 
filings. Relatively well-behaved to the East and West, but spiky in the 
extreme close to the poles.


John Woodgate OOO-Own Opinions Only
J M Woodgate and Associates www.woodjohn.uk
Rayleigh, Essex UK

On 2018-03-05 18:51, Patrick wrote:
re: Mr. Woodgate, and quoting...  " +/- 20% doesn't seem to be enough 
to explain the reported result "


Hmmm.
I would say that if the big 20% problem is not fixed, then the smaller 
problems remain hidden.


The probe cal is the largest problem.
Solve it first, then measure again and find the next largest problem.
Keep going until the problems are small enough to no longer matter.

I know, it sounds open-ended, but most lab debug problems are that way.
Right up until you find that last one - then everything is clear.

Isn't engineering fun?


On Mon, Mar 5, 2018 at 9:19 AM, John Woodgate > wrote:


+/- 20% doesn't seem to be enough to explain the reported result.
After all, assuming the +/- 20% is off the spectrum analyser, 1.2
is +1.6 dB and 0.8 is -1.9 dB. These are small, but not
negligible. If the +/-20% relates to power, they are even smaller
in dB, of course.

John Woodgate OOO-Own Opinions Only
J M Woodgate and Associateswww.woodjohn.uk 
Rayleigh, Essex UK

On 2018-03-05 15:57, Patrick wrote:

Hi David -

I had this same problem.
I'm actually glad to see another engineer looking into this!
The answer is not test setup,
    not ground plane,
    not distance to tabletop, etc.
Each of those can be significant, and should be controlled, but...


The problem you describe sounds exactly like one I had two years ago.
If it is the same problem, the root cause is the *probe calibration*.
The "normal" calibration data that every cal lab provides is too
course.
It hides (skips over) resonances in the probes.
Only a finer calibration step size will resolve this problem.


Here is my abbreviated story...

I started with data just like yours.
I had 6 probes: they were two model FP4000, and four of the HI6053.

... 

The root cause is the "normal" cal.
It uses a course step size in frequency.
When it is too course, it misses resonances in the probe.
Those resonances are significant, as much as +/- 20% in my equipment.

To prove this, I sent a probe out for "enhanced" cal.
I requested both a "normal" cal and a higher resolution cal.
I asked for 5% steps below 1 GHz and 100 MHz steps above 1 GHz.

When the data came back I plotted the cal factors on top of each
other.
It was obvious.
The course cal points of a "normal" calibration will hide
resonances that are +/- 20% deviations.
(above sentence should be BOLD, UNDERLINE, asterisks)


My conclusion:  Any probe used for accredited test must have
calibration data showing the resonances.
If it doesn't, then the lab is guaranteed to be over-testing and
under-testing.

DM me and I'll be glad to discuss.

Patrick



On Sun, Mar 4, 2018 at 8:33 PM, Schaefer, David
> wrote:

Ken,

This data was not taken with 61000-4-3 primarily in mind. We
do -4-3, but also MIL, RTCA, and ISO testing. I should have
had the probe at least 15 cm for ISO or 30 cm for MIL like
you said, but 10cm is how I took the data.

Uniform field calibrations will be a concern eventually, but
the variance is my problem. This was not four probes set up
on a bench next to each other. This was data with one probe
on the bench, centered in front of the antenna, then removed
and replaced as precisely as possible with the next probe.

So if I do a single point cal for ISO 11452-2, one probe
might tell me 100 V/m and another 140 V/m. I'll get
questioned by customers if they fail one day and pass
another. This also runs into another issue - purchasing
amplifiers. If I specify an amp to reach a desired field
strength but when it shows up we can't hit levels due to
using a different field probe, there will be hell to pay.

Standards are silent on probe orientation as well.  Do you
position the probe to maximize field strength? If I can get
an extra half a dB of power by having it an angle instead of
straight on, why not do that? I can save that amplifier cost
- at least until I get a 

Re: [PSES] Field probe calibration

[John Woodgate]

See below.

John Woodgate OOO-Own Opinions Only
J M Woodgate and Associates www.woodjohn.uk
Rayleigh, Essex UK

On 2018-03-05 18:10, Patrick wrote:

Well, some of us have to consider other requirements, not just EN's.

What if the test is -461, or DO-160 ?
And what if the requirement is 200 V/m ?

As everyone knows, those require a pre-test verification, not a 
requirement for "uniform field"?


So a 20% error gives anywhere from 160 V/m to 240 V/m.
JMW: Nevertheless, these are the same dB differences as I posted. If 
there is no better solution, increase the field strength until you are 
sure it is sufficient. There is no way your are going to finagle the 
laws of physics to get closely consistent results in near-field 
conditions. You can regard your reported results as 'additional 
calibration factors', applicable only to that exact set-up in which they 
were measured.

A 600 V/m target is anywhere from 480 V/m to 720 V/m.

Is that insignificant?
Maybe, maybe not.
Depends on you and your customer.
JMW: It's still a range of -1.9 dB to +1.6 dB. If 3.5 dB is crucial, the 
product is probably too near the limit for comfort, unless it's a one-off.


I recommend to always check a test labs calibration factors.
If the factors don't show the resonances, then there are built in errors.
An informed decision can be made whether to accept, or move to another 
lab.


Would you agree, as an engineer, its always better to have the data, 
then to operate in the blind?
JMW: Your minor typo makes that a very profound question. People do 
exactly that. They have the data but do not analyse its significance.

This thread is too long, so I have attenuated it.




-

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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] Field probe calibration

[Patrick]

Well, some of us have to consider other requirements, not just EN's.

What if the test is -461, or DO-160 ?
And what if the requirement is 200 V/m ?

As everyone knows, those require a pre-test verification, not a requirement
for "uniform field"?

So a 20% error gives anywhere from 160 V/m to 240 V/m.
A 600 V/m target is anywhere from 480 V/m to 720 V/m.

Is that insignificant?
Maybe, maybe not.
Depends on you and your customer.

I recommend to always check a test labs calibration factors.
If the factors don't show the resonances, then there are built in errors.
An informed decision can be made whether to accept, or move to another lab.

Would you agree, as an engineer, its always better to have the data, then
to operate in the blind?


On Mon, Mar 5, 2018 at 10:21 AM, Ken Javor 
wrote:

> I am totally with John Woodgate on this – 20% deltas are insignificant in
> the larger picture. I only used 61000-4-3 to demonstrate the fallacy of
> worrying about such small deviations when the overall requirement in a
> really well-designed and expensive chamber is +6, - 0 dB. Consider the type
> of absorber used, the limited frequency range (80 – 1000 MHz), the total
> lack of conducting material, and the fact that 25% of the UFA may be
> excluded from the 6 dB variation.
>
> Your variations are well within that tolerance, and your room and set-up
> nowhere near that good.  If you want better than what you have, you will
> need a chamber and set-up much better than that for 61000-4-3 –
> impractical, to say the least.
>
> The point is, make sure you have enough amplifier to do the job with some
> margin. That’s as good as you are going to get.
>
> Ken Javor
> Phone: (256) 650-5261
>
>
> --
> *From: *John Woodgate 
> *Reply-To: *John Woodgate 
> *Date: *Mon, 5 Mar 2018 16:19:10 +
> *To: *
> *Subject: *Re: [PSES] Field probe calibration
>
>
>
> +/- 20% doesn't seem to be enough to explain the reported result. After
> all, assuming the +/- 20% is off the spectrum analyser, 1.2 is +1.6 dB and
> 0.8 is -1.9 dB. These are small, but not negligible. If the +/-20% relates
> to power, they are even smaller in dB, of course.
>
>
> John Woodgate OOO-Own Opinions Only
> J M Woodgate and Associates www.woodjohn.uk 
> 
> Rayleigh, Essex UK
>
> On 2018-03-05 15:57, Patrick wrote:
>
>
>
>
> Hi David -
>
>
>
> I had this same problem.
>
> I'm actually glad to see another engineer looking into this!
>
> The answer is not test setup,
>
>
> not ground plane,
>
> not distance to tabletop, etc.
>
>
> Each of those can be significant, and should be controlled, but...
>
>
>
>
>
>
>
>
> The problem you describe sounds exactly like one I had two years ago.
>
> If it is the same problem, the root cause is the *probe calibration*.
>
> The "normal" calibration data that every cal lab provides is too course.
>
> It hides (skips over) resonances in the probes.
>
> Only a finer calibration step size will resolve this problem.
>
>
>
>
>
>
>
> Here is my abbreviated story...
>
>
>
>
>
> I started with data just like yours.
>
> I had 6 probes: they were two model FP4000, and four of the HI6053.
>
>
>
>
> ...  amplifiers, chambers, height above table, orientation, etc>
>
>
>
>
> The root cause is the "normal" cal.
>
> It uses a course step size in frequency.
>
> When it is too course, it misses resonances in the probe.
>
> Those resonances are significant, as much as +/- 20% in my equipment.
>
>
>
>
> To prove this, I sent a probe out for "enhanced" cal.
>
> I requested both a "normal" cal and a higher resolution cal.
>
> I asked for 5% steps below 1 GHz and 100 MHz steps above 1 GHz.
>
>
>
>
> When the data came back I plotted the cal factors on top of each other.
>
> It was obvious.
>
> The course cal points of a "normal" calibration will hide resonances that
> are +/- 20% deviations.
>
>
> (above sentence should be BOLD, UNDERLINE, asterisks)
>
>
>
>
>
>
>
> My conclusion:  Any probe used for accredited test must have calibration
> data showing the resonances.
>
> If it doesn't, then the lab is guaranteed to be over-testing and
> under-testing.
>
>
>
>
> DM me and I'll be glad to discuss.
>
>
>
>
> Patrick
>
>
>
>
>
>
>
>
>
>
> On Sun, Mar 4, 2018 at 8:33 PM, Schaefer, David 
> wrote:
>
>
> Ken,
>
>  This data was not taken with 61000-4-3 primarily in mind. We do -4-3, but
> also MIL, RTCA, and ISO testing. I should have had the probe at least 15 cm
> for ISO or 30 cm for MIL like you said, but 10cm is how I took the data.
>
>  Uniform field calibrations will be a concern eventually, but the variance
> is my problem. This was not four probes set up on a bench next to each
> other. This was data with one probe on the bench, centered in front of the
> antenna, then removed and replaced as precisely as possible with the next
> probe.
>
>  So if I do 

Re: [PSES] Field probe calibration

[Ken Javor]

I am totally with John Woodgate on this ­ 20% deltas are insignificant in
the larger picture. I only used 61000-4-3 to demonstrate the fallacy of
worrying about such small deviations when the overall requirement in a
really well-designed and expensive chamber is +6, - 0 dB. Consider the type
of absorber used, the limited frequency range (80 ­ 1000 MHz), the total
lack of conducting material, and the fact that 25% of the UFA may be
excluded from the 6 dB variation.

Your variations are well within that tolerance, and your room and set-up
nowhere near that good.  If you want better than what you have, you will
need a chamber and set-up much better than that for 61000-4-3 ­ impractical,
to say the least.

The point is, make sure you have enough amplifier to do the job with some
margin. That¹s as good as you are going to get.

Ken Javor
Phone: (256) 650-5261



From: John Woodgate 
Reply-To: John Woodgate 
Date: Mon, 5 Mar 2018 16:19:10 +
To: 
Subject: Re: [PSES] Field probe calibration

   

+/- 20% doesn't seem to be enough to explain the reported result. After all,
assuming the +/- 20% is off the spectrum analyser, 1.2 is +1.6 dB and 0.8 is
-1.9 dB. These are small, but not negligible. If the +/-20% relates to
power, they are even smaller in dB, of course.
 
 
John Woodgate OOO-Own Opinions Only
J M Woodgate and Associates www.woodjohn.uk 
Rayleigh, Essex UK
 
On 2018-03-05 15:57, Patrick wrote:
 
 
>  
> Hi David -  
> 
>  
>  
> I had this same problem.  
>  
> I'm actually glad to see another engineer looking into this!
>  
> The answer is not test setup,
>  
>  
>     not ground plane, 
>  
>     not distance to tabletop, etc.  
>  
>  
> Each of those can be significant, and should be controlled, but...
>  
>  
> 
>  
>  
> 
>  
>  
> The problem you describe sounds exactly like one I had two years ago.
>  
> If it is the same problem, the root cause is the *probe calibration*.
>  
> The "normal" calibration data that every cal lab provides is too course.
>  
> It hides (skips over) resonances in the probes.
>  
> Only a finer calibration step size will resolve this problem.
>  
> 
>  
>  
> 
>  
>  
> Here is my abbreviated story...
>  
>  
> 
>  
>  
> I started with data just like yours.
>  
> I had 6 probes: they were two model FP4000, and four of the HI6053.
>  
> 
>  
>  
> ...  amplifiers, chambers, height above table, orientation, etc>
>  
> 
>  
>  
> The root cause is the "normal" cal.
>  
> It uses a course step size in frequency.
>  
> When it is too course, it misses resonances in the probe.
>  
> Those resonances are significant, as much as +/- 20% in my equipment.
>  
> 
>  
>  
> To prove this, I sent a probe out for "enhanced" cal.
>  
> I requested both a "normal" cal and a higher resolution cal.
>  
> I asked for 5% steps below 1 GHz and 100 MHz steps above 1 GHz.
>  
> 
>  
>  
> When the data came back I plotted the cal factors on top of each other.
>  
> It was obvious.
>  
> The course cal points of a "normal" calibration will hide resonances that are
> +/- 20% deviations.
>  
>  
> (above sentence should be BOLD, UNDERLINE, asterisks)
>  
> 
>  
>  
> 
>  
>  
> My conclusion:  Any probe used for accredited test must have calibration data
> showing the resonances.
>  
> If it doesn't, then the lab is guaranteed to be over-testing and
> under-testing.
>  
> 
>  
>  
> DM me and I'll be glad to discuss.
>  
> 
>  
>  
> Patrick
>  
> 
>  
>  
> 
>  
>  
>  
> 
>  
> On Sun, Mar 4, 2018 at 8:33 PM, Schaefer, David  wrote:
>  
>> Ken,
>>  
>>  This data was not taken with 61000-4-3 primarily in mind. We do -4-3, but
>> also MIL, RTCA, and ISO testing. I should have had the probe at least 15 cm
>> for ISO or 30 cm for MIL like you said, but 10cm is how I took the data.
>>  
>>  Uniform field calibrations will be a concern eventually, but the variance is
>> my problem. This was not four probes set up on a bench next to each other.
>> This was data with one probe on the bench, centered in front of the antenna,
>> then removed and replaced as precisely as possible with the next probe.
>>  
>>  So if I do a single point cal for ISO 11452-2, one probe might tell me 100
>> V/m and another 140 V/m. I'll get questioned by customers if they fail one
>> day and pass another. This also runs into another issue - purchasing
>> amplifiers. If I specify an amp to reach a desired field strength but when it
>> shows up we can't hit levels due to using a different field probe, there will
>> be hell to pay.
>>  
>>  Standards are silent on probe orientation as well.  Do you position the
>> probe to maximize field strength? If I can get an extra half a dB of power by
>> having it an angle instead of straight on, why not do that? I can save that
>> amplifier cost - at least until I get a new probe. The calibrations don't
>> seem to mean that much based on my data, so with a composite 

Re: [PSES] Field probe calibration

[John Woodgate]

+/- 20% doesn't seem to be enough to explain the reported result. After 
all, assuming the +/- 20% is off the spectrum analyser, 1.2 is +1.6 dB 
and 0.8 is -1.9 dB. These are small, but not negligible. If the +/-20% 
relates to power, they are even smaller in dB, of course.


John Woodgate OOO-Own Opinions Only
J M Woodgate and Associates www.woodjohn.uk
Rayleigh, Essex UK

On 2018-03-05 15:57, Patrick wrote:

Hi David -

I had this same problem.
I'm actually glad to see another engineer looking into this!
The answer is not test setup,
    not ground plane,
    not distance to tabletop, etc.
Each of those can be significant, and should be controlled, but...


The problem you describe sounds exactly like one I had two years ago.
If it is the same problem, the root cause is the *probe calibration*.
The "normal" calibration data that every cal lab provides is too course.
It hides (skips over) resonances in the probes.
Only a finer calibration step size will resolve this problem.


Here is my abbreviated story...

I started with data just like yours.
I had 6 probes: they were two model FP4000, and four of the HI6053.

... antennas, amplifiers, chambers, height above table, orientation, etc>


The root cause is the "normal" cal.
It uses a course step size in frequency.
When it is too course, it misses resonances in the probe.
Those resonances are significant, as much as +/- 20% in my equipment.

To prove this, I sent a probe out for "enhanced" cal.
I requested both a "normal" cal and a higher resolution cal.
I asked for 5% steps below 1 GHz and 100 MHz steps above 1 GHz.

When the data came back I plotted the cal factors on top of each other.
It was obvious.
The course cal points of a "normal" calibration will hide resonances 
that are +/- 20% deviations.

(above sentence should be BOLD, UNDERLINE, asterisks)


My conclusion:  Any probe used for accredited test must have 
calibration data showing the resonances.
If it doesn't, then the lab is guaranteed to be over-testing and 
under-testing.


DM me and I'll be glad to discuss.

Patrick



On Sun, Mar 4, 2018 at 8:33 PM, Schaefer, David > wrote:


Ken,

This data was not taken with 61000-4-3 primarily in mind. We do
-4-3, but also MIL, RTCA, and ISO testing. I should have had the
probe at least 15 cm for ISO or 30 cm for MIL like you said, but
10cm is how I took the data.

Uniform field calibrations will be a concern eventually, but the
variance is my problem. This was not four probes set up on a bench
next to each other. This was data with one probe on the bench,
centered in front of the antenna, then removed and replaced as
precisely as possible with the next probe.

So if I do a single point cal for ISO 11452-2, one probe might
tell me 100 V/m and another 140 V/m. I'll get questioned by
customers if they fail one day and pass another. This also runs
into another issue - purchasing amplifiers. If I specify an amp to
reach a desired field strength but when it shows up we can't hit
levels due to using a different field probe, there will be hell to
pay.

Standards are silent on probe orientation as well.  Do you
position the probe to maximize field strength? If I can get an
extra half a dB of power by having it an angle instead of straight
on, why not do that? I can save that amplifier cost - at least
until I get a new probe. The calibrations don't seem to mean that
much based on my data, so with a composite reading whichever probe
orientation gives me the highest field should be ok.

Also, any replies I make may be delayed. It seems like I usually
see a 4+ hour delay between when I email the listserve, and when
it is delivered.

Thanks,

David Schaefer


From: Ken Javor [mailto:ken.ja...@emccompliance.com
]
Sent: Sunday, March 04, 2018 12:17 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG 
Subject: Re: [PSES] Field probe calibration

In turn:

It is not surprising at all that it takes less power to generate
the vertical field than the horizontal field. That's the effect of
the conducting ground plane. The OP doesn't say what spec they are
working to, but that is why MIL-STD-461 below 1 GHz has the probe
30 cm above the ground plane, to limit that effect.

Comments, such as Gert Gremmen's, that measurements in the
presence of a ground plane (or any conducting structure) are
useless, are themselves useless.  The comment reflects a
difference in standards of value.  If one is starving, food is the
most important priority. If one is asphyxiating, oxygen is the
primary need.  It is logically incorrect for two people suffering
these two conditions to point at each other and say the other one
is wrong about his priorities: they are both correct within the
scope of 

Re: [PSES] Field probe calibration

[Patrick]

Hi David -

I had this same problem.
I'm actually glad to see another engineer looking into this!
The answer is not test setup,
not ground plane,
not distance to tabletop, etc.
Each of those can be significant, and should be controlled, but...


The problem you describe sounds exactly like one I had two years ago.
If it is the same problem, the root cause is the *probe calibration*.
The "normal" calibration data that every cal lab provides is too course.
It hides (skips over) resonances in the probes.
Only a finer calibration step size will resolve this problem.


Here is my abbreviated story...

I started with data just like yours.
I had 6 probes: they were two model FP4000, and four of the HI6053.

... 

The root cause is the "normal" cal.
It uses a course step size in frequency.
When it is too course, it misses resonances in the probe.
Those resonances are significant, as much as +/- 20% in my equipment.

To prove this, I sent a probe out for "enhanced" cal.
I requested both a "normal" cal and a higher resolution cal.
I asked for 5% steps below 1 GHz and 100 MHz steps above 1 GHz.

When the data came back I plotted the cal factors on top of each other.
It was obvious.
The course cal points of a "normal" calibration will hide resonances that
are +/- 20% deviations.
(above sentence should be BOLD, UNDERLINE, asterisks)


My conclusion:  Any probe used for accredited test must have calibration
data showing the resonances.
If it doesn't, then the lab is guaranteed to be over-testing and
under-testing.

DM me and I'll be glad to discuss.

Patrick



On Sun, Mar 4, 2018 at 8:33 PM, Schaefer, David  wrote:

> Ken,
>
> This data was not taken with 61000-4-3 primarily in mind. We do -4-3, but
> also MIL, RTCA, and ISO testing. I should have had the probe at least 15 cm
> for ISO or 30 cm for MIL like you said, but 10cm is how I took the data.
>
> Uniform field calibrations will be a concern eventually, but the variance
> is my problem. This was not four probes set up on a bench next to each
> other. This was data with one probe on the bench, centered in front of the
> antenna, then removed and replaced as precisely as possible with the next
> probe.
>
> So if I do a single point cal for ISO 11452-2, one probe might tell me 100
> V/m and another 140 V/m. I'll get questioned by customers if they fail one
> day and pass another. This also runs into another issue - purchasing
> amplifiers. If I specify an amp to reach a desired field strength but when
> it shows up we can't hit levels due to using a different field probe, there
> will be hell to pay.
>
> Standards are silent on probe orientation as well.  Do you position the
> probe to maximize field strength? If I can get an extra half a dB of power
> by having it an angle instead of straight on, why not do that? I can save
> that amplifier cost - at least until I get a new probe. The calibrations
> don't seem to mean that much based on my data, so with a composite reading
> whichever probe orientation gives me the highest field should be ok.
>
> Also, any replies I make may be delayed. It seems like I usually see a 4+
> hour delay between when I email the listserve, and when it is delivered.
>
> Thanks,
>
> David Schaefer
>
>
> From: Ken Javor [mailto:ken.ja...@emccompliance.com]
> Sent: Sunday, March 04, 2018 12:17 PM
> To: EMC-PSTC@LISTSERV.IEEE.ORG
> Subject: Re: [PSES] Field probe calibration
>
> In turn:
>
> It is not surprising at all that it takes less power to generate the
> vertical field than the horizontal field.  That's the effect of the
> conducting ground plane. The OP doesn't say what spec they are working to,
> but that is why MIL-STD-461 below 1 GHz has the probe 30 cm above the
> ground plane, to limit that effect.
>
> Comments, such as Gert Gremmen's, that measurements in the presence of a
> ground plane (or any conducting structure) are useless, are themselves
> useless.  The comment reflects a difference in standards of value.  If one
> is starving, food is the most important priority. If one is asphyxiating,
> oxygen is the primary need.  It is logically incorrect for two people
> suffering these two conditions to point at each other and say the other one
> is wrong about his priorities: they are both correct within the scope of
> their individual circumstances. The only logical observation that can be
> made is that oxygen needs to be supplied sooner than food, if the standard
> of value is immediate survival.
>
> In the world of goods slated for use in home, office and factory, the coin
> of the realm is accuracy and minimum uncertainty, so that qualifications
> everywhere result in a level economic playing field. Required field
> intensities (1/3/10 V/m) are very low compared to the world of vehicle EMI
> testing (as high as 200 V/m, sometimes beyond), so that (again relative)
> low power amplifiers may be used with antennas separated from the test area
> by three meters instead of one, facilitating the