The IEC likely has, long-ago, published a standardized test method for power supply parameters including measurement of output noise and ripple. If there isn't one, then this method might be of some use to you.
For measuring peak, periodic noise from a switching power supply output terminal pair, I found that removing the scope probe ground lead and pulling the probe clip head and then carefully wrapping a very short length of bus wire around the grounded ferrule near the tip of the scope probe works quite well. That test method in a professional setting provided my previous employer with repeatable results when observing those very narrow spikes on the dc output. Set scope channel in ac coupling mode and scope probe set to 1X for a conveniently limited measurement bandwidth ( a few MHz ) and a very short ground lead. Your customers may get very different results, but if you need to publish a peak or peak-peak output "noise" specification for a power supply, then you'll need a carefully define and document a test method for an "apples to apples' comparison with competing products. About 30 years ago, there was a rumour circulating in the industry that a major power supply brand used a scope probe connected to a 1uF film capacitor at the end of 1 foot of twist pair wire for their peak-to-peak noise specification. Probably as good as anything we did at the time. However, an industry standard test method is the best way to go. Ralph From: Brian Gregory <brian_greg...@netzero.net> Sent: January 6, 2025 10:27 AM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: [PSES] Power supply noise Doug, > 1+ Volt peak-to-peak spikes on the scope at the fundamental switching frequency of the power supply. > What is the first thing you do? > Doug Smith 1st thing I'd do is connect both probes together at each P.S. terminal, one at a time, and see if the noise goes away. If it doesn't, that 1Vpp reading is due to your measurement set up. It's a baby step, but it's served me in the past. Colorado Brian _____ This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to EMC-PSTC@LISTSERV.IEEE.ORG <mailto:EMC-PSTC@LISTSERV.IEEE.ORG> All emc-pstc postings are archived and searchable on the web at: https://www.mail-archive.com/emc-pstc@listserv.ieee.org/ <https://www.mail-archive.com/emc-pstc@listserv.ieee.org/%20> Website: https://ewh.ieee.org/soc/pses/ <https://ewh.ieee.org/soc/pses/> Instructions: https://ewh.ieee.org/soc/pses/list.html (including how to unsubscribe) <https://ewh.ieee.org/soc/pses/list.html> List rules: https://ewh.ieee.org/soc/pses/listrules.html For help, send mail to the list administrators: Mike Sherman at: msherma...@comcast.net <mailto:msherma...@comcast.net> Rick Linford at: linf...@ieee.org <mailto:linf...@ieee.org> For policy questions, send mail to: Jim Bacher at: j.bac...@ieee.org <mailto:j.bac...@ieee.org> _____ To unsubscribe from the EMC-PSTC list, click the following link: https://listserv.ieee.org/cgi-bin/wa?SUBED1=EMC-PSTC <https://listserv.ieee.org/cgi-bin/wa?SUBED1=EMC-PSTC&A=1> &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 EMC-PSTC@LISTSERV.IEEE.ORG All emc-pstc postings are archived and searchable on the web at: https://www.mail-archive.com/emc-pstc@listserv.ieee.org/ 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: msherma...@comcast.net Rick Linford at: linf...@ieee.org For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> _________________________________________________ To unsubscribe from the EMC-PSTC list, click the following link: https://listserv.ieee.org/cgi-bin/wa?SUBED1=EMC-PSTC&A=1
