Back in the 1980s I had a variation in system measurements between labs.
Management decided the lab I used wasn't any good. In the process of trying
to convince management variations were normal, I came to the conclusion
that measuring systems at different labs would likely have a +5 to -7 dB
variations.
None of our test equipment is perfectly flat. No one calibrates every Hz to
account for those imperfections. The frequency being measured is typically
not on any of the calibrated frequencies.
For testing a system, equipment and cable variations can impact their
emmisions significantly. I have seen over 20 dB of variation due to the
variations. How much effort was made to peak signals?
Then is the test equipment measurement operator an avid Ham DXer (chases
weak signals to talk to far away stations)? Reason is a Ham will likely do
a more accurate peaking of rotation and height of the search antennas.
I have had one government lab fail to compensate for a preamp when
reporting levels and said the product failed. I had the agent pull it back
for a few days, then take it back and it passed with no changes. So some
errors can be to using the wrong calibration factors when calculating the
levels.
Jim Bacher, WB8VSU
[email protected] or [email protected]
JBRC Consulting LLC
Product EMC & Regulatory Consultant
https://www.trc.guru/ email:[email protected]
IEEE Life Senior Member
On October 8, 2024 11:14:28 AM David Schaefer
<[email protected]> wrote:
Harry Hodes gave a presentation at the C63 meetings last week on
proficiency testing. He runs the ACIL PT program, and the data he shared
showed a ton of variance. Many labs were in I think +/-3-4 dB range, but
there were outliers – the worst cases being one lab reading 30-40 dB high,
another 30-40 dB low. If I recall correctly for one PT program 95 labs
participated and around 10 were outside the expected tolerance.
Doing a check of the measurement system prior to testing is critical. A
comb gen scan takes only a few minutes but should catch these egregious errors.
David Schaefer
Technical Manager
Element Materials Technology
9349 W Broadway Ave
Brooklyn Park
,
MN
55445
,
United States
O +1 612 638 5136
ext. 10461
[email protected]
www.element.com
From: doug emcesd.com <[email protected]>
Sent: Monday, October 7, 2024 6:08 PM
To: [email protected]
Subject: [PSES] technical musings
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 the TOC if you are in any doubt
about this email.
I have seen differences of 9 dB on the same measurement on an EUT and comb
generator by different accredited labs!
Doug
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
[email protected]
All emc-pstc postings are archived and searchable on the web at:
https://www.mail-archive.com/[email protected]/
Website: https://ewh.ieee.org/soc/pses/
Instructions: https://ewh.ieee.org/soc/pses/list.html (including how to
unsubscribe)
List rules: https://ewh.ieee.org/soc/pses/listrules.html
For help, send mail to the list administrators:
Mike Sherman at: [email protected]
Rick Linford at: [email protected]
For policy questions, send mail to:
Jim Bacher at: [email protected]
To unsubscribe from the EMC-PSTC list, click the following link:
https://listserv.ieee.org/cgi-bin/wa?SUBED1=EMC-PSTC&A=1
Disclaimer
This email is sent on behalf of Element Materials Technology Group Limited
or the relevant group company with which you are dealing (together,
Element). Element Materials Technology Group Limited is a limited company
registered in England and Wales with registered number 09915743. Its
registered office and its principal place of business is at 3rd Floor,
Davidson Building, 5 Southampton Street, London, United Kingdom, WC2E 7HA.
Element cannot accept responsibility for any loss or damage sustained as a
result of viruses or malware and the recipient must ensure that the email
and attachments are virus and malware free. Emails and attachments are
opened at your own risk.
The information transferred is intended only for the person or entity to
which it is addressed and may contain confidential and/or privileged
material. Transmission of this email is not intended to waive
confidentiality and/or privilege.
The contents of this email are subject to contract and do not contain an
offer that is capable of acceptance. Unless otherwise agreed in writing
with you, the Element Standard Terms of Business for the relevant group
company apply in respect of any services provided to you, including advice
given to you by email. The Standard Terms of Business are available on
request and can be found at https://www.element.com/terms/terms-and-conditions
For information about how we process data and monitor communications please
see our Privacy statement at https://www.element.com/terms/privacy-statement
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
[email protected]
All emc-pstc postings are archived and searchable on the web at:
https://www.mail-archive.com/[email protected]/
Website: https://ewh.ieee.org/soc/pses/
Instructions: https://ewh.ieee.org/soc/pses/list.html (including how to
unsubscribe)
List rules: https://ewh.ieee.org/soc/pses/listrules.html
For help, send mail to the list administrators:
Mike Sherman at: [email protected]
Rick Linford at: [email protected]
For policy questions, send mail to:
Jim Bacher at: [email protected]
To unsubscribe from the EMC-PSTC list, click the following link:
https://listserv.ieee.org/cgi-bin/wa?SUBED1=EMC-PSTC&A=1
-
----------------------------------------------------------------
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
[email protected]
All emc-pstc postings are archived and searchable on the web at:
https://www.mail-archive.com/[email protected]/
Website: https://ewh.ieee.org/soc/pses/
Instructions: https://ewh.ieee.org/soc/pses/list.html (including how to
unsubscribe)
List rules: https://ewh.ieee.org/soc/pses/listrules.html
For help, send mail to the list administrators:
Mike Sherman at: [email protected]
Rick Linford at: [email protected]
For policy questions, send mail to:
Jim Bacher: <[email protected]>
_________________________________________________
To unsubscribe from the EMC-PSTC list, click the following link:
https://listserv.ieee.org/cgi-bin/wa?SUBED1=EMC-PSTC&A=1
