[PSES] thoughts on ESD test lab problems

2023-08-10 Thread doug emcesd.com
Hi All,

Just a couple of thoughts on what a good lab should do for ESD testing and how 
to protect yourself as a client from test problems.


  1.  Bring an Ohmmeter with you to the lab and measure the resistance from the 
Horizontal Coupling Plane to the Ground Reference Plane. It should be about 2X 
470 K. I have seen both commercial test labs and private labs where these 
resistors are open which can cause a product failure. A good lab should measure 
this value every morning and report the result in your test report..
  2.  The vacuum relay in the ESD simulators have a limited life after which 
the current waveform becomes quite variable and at that point cannot give an 
accurate test of your equipment. Having a valid calibration sticker is close to 
useless as the condition can develop quickly. I have personally seen a rented 
simulator with a valid calibration sticker have this problem with its current 
waveform all over the place from one discharge to another. A good test lab will 
verify this is not happening at the beginning of each day. You as a client can 
tell from a distance by just making a small antenna by extending a coax center 
conductor 6 inches pass the shield to make a small antenna. Better would be to 
make a TEM antenna which does not color its output by its resonances. Connect 
the antenna to a scope of at least 4 GSa/sec sampling rate, preferably higher. 
You don't really care what waveform you get, say from 6 feet away, but each 
discharge of a series of ten should look the same.

More to come! Most test labs I have used over the years made at least one 
mistake that affected the test results. I have had disagreements with labs, 
never lost one of them.

Doug
[https://lh4.googleusercontent.com/_HuR3Ky2TF_XhFHyxnYRmiq7nHQldnMsPNYFaLG6kb5T4y8MeCe-BDC_BscJtSFgszSSjssihHS-pjM3-jwNP8S0CwE-gN8fsRsPkojiAlmpBwb20vIVizS-siCUywW_jqrefbVr]

-

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Re: [PSES] Necessary Lab accreditations, class 2 permissible change

2023-08-10 Thread Ralph McDiarmid
Cord-connected equipment?

 

From: Elliott Martinson  
Sent: Thursday, August 10, 2023 12:27 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] Necessary Lab accreditations, class 2 permissible change

 

If it were to become a leakage current issue, I’d wonder whether the
parasitic inductance [i.e., enclosed loop area] in the current paths through
the Y-Caps could be reduced, as that can often be much more meaningful than
the actual capacitance value. If package choice and layout were already
optimal, one might still be able to parallel 2x the # of caps but cut their
capacitance values in ½  in order to increase the EMC margin without
affecting leakage/touch current?

 

Elliott

 

From: Chester Summers mailto:chester.summ...@ditchwitch.com> > 
Sent: Thursday, August 10, 2023 11:22 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG  
Subject: Re: [PSES] Necessary Lab accreditations, class 2 permissible change

 

Hi, Brian—

 

More margin is good but be sure to check that your leakage/touch current is
still acceptable.  Sometimes striking that balance means living with a
little less emissions margin than an EMC guy would prefer. :)

 

Good luck,

Chet Summers

 

From: Brian Gregory mailto:brian_greg...@netzero.net> > 
Sent: Thursday, August 10, 2023 10:01 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG  
Subject: Re: [PSES] Necessary Lab accreditations, class 2 permissible change

 

Think Before You Click: This email originated outside our organization. 

 

Yes, we increased the Y-Caps to get more margin.  And we did!

So, to qualify for a Class 1 permissive change, we'd need to show before &
after data ?

 

Applying for a Class 2 permissive change, means FCC will look only at the
latest data to be sure it passes?

 

Colorado Brian

-- Original Message --
From: John Woodgate mailto:j...@woodjohn.uk> >
To: EMC-PSTC@LISTSERV.IEEE.ORG  
Subject: Re: [PSES] Necessary Lab accreditations, class 2 permissible change
Date: Thu, 10 Aug 2023 00:02:42 +0100

What are you changing about the Y-caps? If it's just a new supplier and the
caps conform to the required component standard, there is no degradation.
Reducing he capacitance would be a degradation for EMC but not for safety. 

Who determines the class is the person who has all the necessary data. The
test house of surveillance authority check the decision.

On 2023-08-09 23:20, Brian Gregory wrote:

 

 Hello EMC experts,

 

A question came up today about filing new results to FCC for our legacy
product.

 

1.  If the filing is only for FCC, then the lab providing the report does
not need A2LA accreditation,

2.  If the filing is for a safety report, then the lab does need A2LA
accreditation.

 

Have I got that right?

 

We're filing some small board changes, including Y-caps and can't figure out
if this is a Class 2 permissible change, defined as:  " includes those
modifications which degrade the performance characteristics as reported to
the Commission"

 

3.  How or who determines if our change is Class 2 (degraded performance) or
Class 1? 

We think the results are better, but it's not like we got uniformly more
margin across the board.   

 

Thanks!

 

Colorado Brian

720-450-4933


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Re: [PSES] Necessary Lab accreditations, class 2 permissible change

2023-08-10 Thread Elliott Martinson
If it were to become a leakage current issue, I'd wonder whether the parasitic 
inductance [i.e., enclosed loop area] in the current paths through the Y-Caps 
could be reduced, as that can often be much more meaningful than the actual 
capacitance value. If package choice and layout were already optimal, one might 
still be able to parallel 2x the # of caps but cut their capacitance values in 
½  in order to increase the EMC margin without affecting leakage/touch current?

Elliott

From: Chester Summers 
Sent: Thursday, August 10, 2023 11:22 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] Necessary Lab accreditations, class 2 permissible change

Hi, Brian-

More margin is good but be sure to check that your leakage/touch current is 
still acceptable.  Sometimes striking that balance means living with a little 
less emissions margin than an EMC guy would prefer. :)

Good luck,
Chet Summers

From: Brian Gregory 
mailto:brian_greg...@netzero.net>>
Sent: Thursday, August 10, 2023 10:01 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] Necessary Lab accreditations, class 2 permissible change


Think Before You Click: This email originated outside our organization.

Yes, we increased the Y-Caps to get more margin.  And we did!
So, to qualify for a Class 1 permissive change, we'd need to show before & 
after data ?

Applying for a Class 2 permissive change, means FCC will look only at the 
latest data to be sure it passes?

Colorado Brian

-- Original Message --
From: John Woodgate mailto:j...@woodjohn.uk>>
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] Necessary Lab accreditations, class 2 permissible change
Date: Thu, 10 Aug 2023 00:02:42 +0100

What are you changing about the Y-caps? If it's just a new supplier and the 
caps conform to the required component standard, there is no degradation. 
Reducing he capacitance would be a degradation for EMC but not for safety.

Who determines the class is the person who has all the necessary data. The test 
house of surveillance authority check the decision.
On 2023-08-09 23:20, Brian Gregory wrote:

 Hello EMC experts,

A question came up today about filing new results to FCC for our legacy product.

1.  If the filing is only for FCC, then the lab providing the report does not 
need A2LA accreditation,
2.  If the filing is for a safety report, then the lab does need A2LA 
accreditation.

Have I got that right?

We're filing some small board changes, including Y-caps and can't figure out if 
this is a Class 2 permissible change, defined as:  " includes those 
modifications which degrade the performance characteristics as reported to the 
Commission"

3.  How or who determines if our change is Class 2 (degraded performance) or 
Class 1?
We think the results are better, but it's not like we got uniformly more margin 
across the board.

Thanks!

Colorado Brian
720-450-4933


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Re: [PSES] Necessary Lab accreditations, class 2 permissible change

2023-08-10 Thread Chester Summers
Hi, Brian-

More margin is good but be sure to check that your leakage/touch current is 
still acceptable.  Sometimes striking that balance means living with a little 
less emissions margin than an EMC guy would prefer. :)

Good luck,
Chet Summers

From: Brian Gregory 
Sent: Thursday, August 10, 2023 10:01 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] Necessary Lab accreditations, class 2 permissible change


Think Before You Click: This email originated outside our organization.

Yes, we increased the Y-Caps to get more margin.  And we did!
So, to qualify for a Class 1 permissive change, we'd need to show before & 
after data ?

Applying for a Class 2 permissive change, means FCC will look only at the 
latest data to be sure it passes?

Colorado Brian

-- Original Message --
From: John Woodgate mailto:j...@woodjohn.uk>>
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] Necessary Lab accreditations, class 2 permissible change
Date: Thu, 10 Aug 2023 00:02:42 +0100

What are you changing about the Y-caps? If it's just a new supplier and the 
caps conform to the required component standard, there is no degradation. 
Reducing he capacitance would be a degradation for EMC but not for safety.

Who determines the class is the person who has all the necessary data. The test 
house of surveillance authority check the decision.
On 2023-08-09 23:20, Brian Gregory wrote:

 Hello EMC experts,

A question came up today about filing new results to FCC for our legacy product.

1.  If the filing is only for FCC, then the lab providing the report does not 
need A2LA accreditation,
2.  If the filing is for a safety report, then the lab does need A2LA 
accreditation.

Have I got that right?

We're filing some small board changes, including Y-caps and can't figure out if 
this is a Class 2 permissible change, defined as:  " includes those 
modifications which degrade the performance characteristics as reported to the 
Commission"

3.  How or who determines if our change is Class 2 (degraded performance) or 
Class 1?
We think the results are better, but it's not like we got uniformly more margin 
across the board.

Thanks!

Colorado Brian
720-450-4933


This message is from the IEEE Product Safety Engineering Society emc-pstc 
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Re: [PSES] Necessary Lab accreditations, class 2 permissible change

2023-08-10 Thread David Schaefer
Certification activities in the USA are handled by TCBs. Most test labs either 
have a separate TCB group, or work with a specific TCB for approvals. You 
should work with a lab to determine what tests need to be repeated, and take 
the data. Based on the new data the lab can determine if it is a Class 1 or 
Class 2. For a Class 2 the TCB will do a filing with the FCC. For a Class 1 you 
just need to keep the data on hand internally to prove the change was 
investigated.



[cid:image439490.jpg@6431776C.1BB6A68A]
David Schaefer​
Technical Manager
Element Materials Technology
9349 W Broadway Ave
Brooklyn Park
,
MN
55445
,
United States
O +1 612 638 5136
ext. 10461
david.schae...@element.com
www.element.com
[cid:image333160.png@4AF050CB.ADA894E2]
[cid:image439401.png@6BA00905.6FD1FCB6]
[cid:image942733.png@1540D0F8.60649E36]
[cid:image077280.png@866A6847.6767A7AC]
[cid:image873315.jpg@A94560F1.CC1DFEA7]
From: Brian Gregory [mailto:brian_greg...@netzero.net]
Sent: Thursday, August 10, 2023 10:01 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] Necessary Lab accreditations, class 2 permissible change


CAUTION:This email originated from outside of Element Materials Technology. DO 
NOT click links or open attachments unless you recognize the sender and know 
the content is safe. Please contact IT Service Desk if you are in any doubt 
about this email.

Yes, we increased the Y-Caps to get more margin.  And we did!
So, to qualify for a Class 1 permissive change, we'd need to show before & 
after data ?

Applying for a Class 2 permissive change, means FCC will look only at the 
latest data to be sure it passes?

Colorado Brian

-- Original Message --
From: John Woodgate mailto:j...@woodjohn.uk>>
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] Necessary Lab accreditations, class 2 permissible change
Date: Thu, 10 Aug 2023 00:02:42 +0100

What are you changing about the Y-caps? If it's just a new supplier and the 
caps conform to the required component standard, there is no degradation. 
Reducing he capacitance would be a degradation for EMC but not for safety.

Who determines the class is the person who has all the necessary data. The test 
house of surveillance authority check the decision.
On 2023-08-09 23:20, Brian Gregory wrote:

 Hello EMC experts,

A question came up today about filing new results to FCC for our legacy product.

1.  If the filing is only for FCC, then the lab providing the report does not 
need A2LA accreditation,
2.  If the filing is for a safety report, then the lab does need A2LA 
accreditation.

Have I got that right?

We're filing some small board changes, including Y-caps and can't figure out if 
this is a Class 2 permissible change, defined as:  " includes those 
modifications which degrade the performance characteristics as reported to the 
Commission"

3.  How or who determines if our change is Class 2 (degraded performance) or 
Class 1?
We think the results are better, but it's not like we got uniformly more margin 
across the board.

Thanks!

Colorado Brian
720-450-4933


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 
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Re: [PSES] Necessary Lab accreditations, class 2 permissible change

2023-08-10 Thread Brian Gregory
 Yes, we increased the Y-Caps to get more margin.  And we did!So, to qualify 
for a Class 1 permissive change, we'd need to show before & after data ? 
Applying for a Class 2 permissive change, means FCC will look only at the 
latest data to be sure it passes? Colorado Brian

-- Original Message --
From: John Woodgate 
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] Necessary Lab accreditations, class 2 permissible change
Date: Thu, 10 Aug 2023 00:02:42 +0100


What are you changing about the Y-caps? If it's just a new supplier and the 
caps conform to the required component standard, there is no degradation. 
Reducing he capacitance would be a degradation for EMC but not for safety. 
 
Who determines the class is the person who has all the necessary data. The test 
house of surveillance authority check the decision.
 
On 2023-08-09 23:20, Brian Gregory wrote:  Hello EMC experts, A question came 
up today about filing new results to FCC for our legacy product. 1.  If the 
filing is only for FCC, then the lab providing the report does not need A2LA 
accreditation,2.  If the filing is for a safety report, then the lab does need 
A2LA accreditation. Have I got that right? We're filing some small board 
changes, including Y-caps and can't figure out if this is a Class 2 permissible 
change, defined as:  " includes those modifications which degrade the 
performance characteristics as reported to the Commission" 3.  How or who 
determines if our change is Class 2 (degraded performance) or Class 1? We think 
the results are better, but it's not like we got uniformly more margin across 
the board.Thanks! Colorado Brian720-450-4933This 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 
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 https://www.mail-archive.com/emc-pstc@listserv.ieee.org/
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Re: [PSES] Necessary Lab accreditations, class 2 permissible change

2023-08-10 Thread David Schaefer
Brian,

Section 2.948 of Part 47 of the CFR requires the lab be accredited when doing 
certification testing.
https://www.ecfr.gov/current/title-47/chapter-I/subchapter-A/part-2/subpart-J/subject-group-ECFRd5ad3b739dbf27a/section-2.948

As for whether it is a Class 1 or Class 2 Permissive change depends on what the 
change is. If you’re only changing out Y caps in the mains filter it is likely 
a Class 1, but you have to have data to back that up. Contact your test lab for 
a discussion about what they think is necessary. KDB 178919 has information 
about permissive changes
https://apps.fcc.gov/oetcf/kdb/forms/FTSSearchResultPage.cfm?id=33013=P

Thanks,


[cid:image123477.jpg@08059ED4.69696CEA]
David Schaefer​
Technical Manager
Element Materials Technology
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From: Brian Gregory [mailto:brian_greg...@netzero.net]
Sent: Wednesday, August 9, 2023 5:20 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: [PSES] Necessary Lab accreditations, class 2 permissible change


CAUTION:This email originated from outside of Element Materials Technology. DO 
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 Hello EMC experts,

A question came up today about filing new results to FCC for our legacy product.

1.  If the filing is only for FCC, then the lab providing the report does not 
need A2LA accreditation,
2.  If the filing is for a safety report, then the lab does need A2LA 
accreditation.

Have I got that right?

We're filing some small board changes, including Y-caps and can't figure out if 
this is a Class 2 permissible change, defined as:  " includes those 
modifications which degrade the performance characteristics as reported to the 
Commission"

3.  How or who determines if our change is Class 2 (degraded performance) or 
Class 1?
We think the results are better, but it's not like we got uniformly more margin 
across the board.

Thanks!

Colorado Brian
720-450-4933


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