Re: Common Mode or Differential Mode
EN 55 022:1998, in the Appendix shows ISNs which suppress the differential mode and give you the common mode only. Does someone know where to buy such ISNs, but in the LISN version? Thanks in advance Rene Charton - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Common Mode or Differential Mode
When testing conducted emissions on a 3-wire (grounded) product, I disconnect the green wire at the EUT. This removes a significant portion of the common-mode signal. Because my testing normally involves power supplies with simple, ungrounded, resistive loads, this is easy to do. If a complex system is being tested, this may mean removing several earth ground connections. WARNING The chassis of the EUT may become 'hot' due to AC line-chassis leakage current, so take appropriate precautions. On Tue, 4 Jan 2000 04:20:29 -0600, rehel...@mmm.com wrote: Are there rules of thumb or a quick and dirty means of determining whether conducted emission noise (or radiated) is common mode or differential mode? Thanks and have a great new year. Bob Heller 3M Company -- Patrick Lawler plaw...@west.net - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Common Mode or Differential Mode
Bob, if you are just trying to identify the type you could connect a boradband scope with hig impedance input from each line to ground, assuming the conductors are carrying AC. The voltages from each side to ground should be nearly identical if the common mode currents are close to the same value, i.e. equal volatges. If there is much difference, you can be sure DM currents are flowing. regards, Ralph Cameron Consultant in EMC and Suppression of consumer electronic equipment (After sale) - Original Message - From: rehel...@mmm.com To: emc-p...@majordomo.ieee.org Sent: Tuesday, January 04, 2000 5:20 AM Subject: Common Mode or Differential Mode Are there rules of thumb or a quick and dirty means of determining whether conducted emission noise (or radiated) is common mode or differential mode? Thanks and have a great new year. Bob Heller 3M Company - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators). - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Common Mode or Differential Mode
Put a current probe around the bundle. What you measure is common mode (a good current probe should have close to 50 dB of dm rejection). In the case of power, the current probe goes around feeder and return. Alternatively, for power you may use a 3-port device such as LISNMATE device which hooks up to each LISN and to your spectrum analyzer and attenuates dm emissions by 50 dB below 30 MHz. The advantage of LISNMATE is that you may compare spectrum analyzer reading directly to the CE limit. -- From: rehel...@mmm.com To: emc-p...@majordomo.ieee.org Subject: Common Mode or Differential Mode Date: Tue, Jan 4, 2000, 2:20 AM Are there rules of thumb or a quick and dirty means of determining whether conducted emission noise (or radiated) is common mode or differential mode? Thanks and have a great new year. Bob Heller 3M Company - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators). - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
RE: Common Mode or Differential Mode
Radiation is always (99.999%) due to CM. Conducted can be either; use LISN Mate or a Current probe. Mark -Original Message- From: rehel...@mmm.com [mailto:rehel...@mmm.com] Sent: Tuesday, January 04, 2000 2:20 AM To: emc-p...@majordomo.ieee.org Subject: Common Mode or Differential Mode Are there rules of thumb or a quick and dirty means of determining whether conducted emission noise (or radiated) is common mode or differential mode? Thanks and have a great new year. Bob Heller 3M Company - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators). - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Common Mode or Differential Mode
Generally, low frequency is dominated by differential mode caused by the current demand of the switcher being imprinted across the impedances of the components; then in the midrange its anybody's guess, but usually common mode, because the capacitors and series impedance elements start to take effect; at high frequency rarely have I seen anything but common mode because the series impedances really start to dominate and even the parasitic capacitances (ie. between cables) dominate. At the low end you can tell which is which by adding components to the line filter: If the source is differential the signal drops dramatically when series elements are added just before the last line to line capacitor. If the source is common mode, the signal drops dramatically as you increase the size of the common mode choke. Note: increasing Y-caps affect both modes sometimes depending on the topology of your filter. Without the experimentation of changing the unit there is a way to quantify common mode versus differential mode emissions by using a LISN which gives you access to both ports simultaneously and use a scope in differential mode (carefully balanced) then take the output of the scope into the spectrum analyzer. Then differential and common mode contributions can be quantified. - Robert - -Original Message- From: rehel...@mmm.com rehel...@mmm.com To: emc-p...@majordomo.ieee.org emc-p...@majordomo.ieee.org List-Post: emc-pstc@listserv.ieee.org Date: Tuesday, January 04, 2000 3:10 AM Subject: Common Mode or Differential Mode Are there rules of thumb or a quick and dirty means of determining whether conducted emission noise (or radiated) is common mode or differential mode? Thanks and have a great new year. Bob Heller 3M Company - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators). - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
