I suggest that if one is interested only in the emissions from the EUT, then a stack of resistors is the easiest way to build a suitable load. If one is interested in functional interaction between power supply and an active load (perhaps DC-DC converter) then okay, but how would you distinguish noise from the load from noise from the EUT? There are so many different types of passive and active loads which power supply could support, where would one start and finish? I think it's very similar why trying to determine how much current THD an EUT produces versus how much is produced by the voltage distortion on the electricity supply. Unless you can determine that a transistorized load bank is "quiet" and doesn't interact with the power supply under test, then I propose that a passive, resistive load is better when measuring conducted or radiated emissions or immunity on an inverter or a converter product.
====================================== Ralph McDiarmid, AScT Compliance Engineering Group Xantrex Technology Inc., _____ Dave: I would imagine that the electronic load is itself a noise source. You are likely seeing the noise of the load, filtered and isolated by the power supply. Further, the power supply might not like the noise of the electronic load, and respond with even more power supply noise. Also, the electronic load may be providing a common mode path for power supply output noise. I generally avoid electronic loads, but it could be argued that a digital load looks a lot more realistic than a stack of non-inductive resistors. You should know what happens when your power supply is feeding real electronics as well as a passive load. Regards, Ed Price [email protected] WB6WSN NARTE Certified EMC Engineer & Technician Electromagnetic Compatibility Lab Cubic Defense Applications San Diego, CA USA 858-505-2780 (Voice) 858-505-1583 (Fax) Military & Avionics EMC Is Our Specialty - - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas [email protected] Mike Cantwell [email protected] For policy questions, send mail to: Jim Bacher: [email protected] David Heald: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
