I am in a discussion and would like to see what the general opinion is. The discuss centers around where to place an external power supply while doing CISPR 22 emissions testing; on the table, on an insulator in close proximity with the ground plane or on the ground plane.
The power supply is auto ranging with an input from 100VAC-250VAC with a dc output, power is feed into power supply from a standard IEC 60320 cord set. The output is non-shielded 2-conductor cable with a barrel connector at the end. The output cable length is about a meter. The following are from CISPR 22 Section 8.1 "the EUT shall be configured, installed and arranged and operated in a manner consistent with typical applications". Section 8.1.1 to paraphrase, find the configuration for the highest emissions. Section 8.1.2 "The EUT situation relative to ground plane shall be equivalent to that occurring in use,". Section 9.3 "Floor-standing EUTs shall be placed on a horizontal metal ground plane,...,but not in metallic contact with the ground plane". Section 9.4 "Equipment designed for both table-top and floor-standing operation shall be tested only in the table-top configuration,". Section 10.4 "Floor-standing EUTs shall be placed directly on the horizontal metal ground plane, the point(s) of contact being consistent with normal use, but separated from the metallic contact with the ground plane by up to 12mm of insulation.". Figure 12 "Test configuration: floor-standing and table-top equipment (radiated measurement) Note 4) EUT and cable shall be insulated from the horizontal metal ground plane." When the power supply is on the table its emissions are 6dB below the class B limit, on a 2mm insulator on the ground plane it is 2dB below class B limit, and when placed on the ground plane it is over the class B limit by 1dB. Reading the rules above it seems I can justify placing the power supply in all three locations. My justification for placing it on the ground plane is that this configuration predominates in the typical end user setup and I must follow the worst case emission configuration. But considering what seem to be conflicting sections in CISPR 22 I would like to see what the general opinions and comments are. Appreciate the responses and help William Morse ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
