The usual reason for doing this is to eliminate testing when the configuration changes.
e.g. If the power remains the same then the thermals will be within the same ball-park. To benefit from this most you should load up the module (extra resistor on each card - or perhaps a dummy card full of extra loads). This validate any configuration drawing UP that power. AND , as we know, improvements never take LESS power. ALTERNATIVELY - they want to know if (under fault conditions) the unit will burn up. That would seem to indicate the old CSA 22.2 No. 220 test of loading each PSU with a Hot - sweaty - variable load and "tuning for maximum smoke"!!! Almost as satisfying as the steel ball test : ^} Within the scheme of things (provided the output waveform is not distorted or has too much ripple) you'll get the same reading whatever instrument you use. If the form factor gets bad then the power level will fall - but that is not the maximum: so you won't want to measure it anyway!!! And fold back usually occurs before then, anyway. Current Probes and Shunts are good - RATED 10 times (ideally) the maximum current you expect. Unless you have a good old-fashioned Moving Iron meter BEFORE you connect your expensive meter. Best regards Gregg From: [email protected] [mailto:[email protected]]On Behalf Of [email protected] Sent: Monday, February 17, 2003 3:19 PM To: [email protected] Subject: Measuring Power Supply Output Current I have been asked by my TUV office to measure the actual output current for each of the 5-7 voltages on my PC power supplies. The purpose of this is to baseline the maximum output current in terms of maximum power, not instantaneous current, for each of the various motherboards we use. On the surface it seemed like a simple exercise of putting a DC current meter in series with each of the outputs. Given that the current demand for each of these outputs is dynamic, corresponding with the processing activity, does it make sense to measure this output current with a True RMS meter? If this is the case, I would assume that the True RMS meter takes the measurement based on some type of a time weighted average or sample time. Do any of you have a feel for how this is calculated? How do manufacturers of these PC supplies address the maximum output current ratings for each voltage. Does this rating take into account PEAK demands for current (or over current)? Thanks Rick Busche Evans & Sutherland [email protected] 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: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
