Charles Grasso wrote: >> The amplitudes fell in just as theory predicted. Encouraged, I then probed the Vcc plane on a product I was working on and was not so happy!! <<
Assuming you are measuring the signal you mean to measure (grin), the reason for using zero span is a sanity check, you know? For analyzer bandwidths greater than that of the signal you are measuring, the SA and the 'scope should show about the same amplitudes. If they don't, you look for a reason. For SA bandwidths less than the signal you are trying to measure, the SA should measure lower amplitudes than the 'scope does, because an oscilloscope sums them all, over its entire bandwidth (whatever that is), while the spectrum analyzer displays only those components of the signal spectrum its bandwidth can include. Simple example: the PEP of an AM radio signal is higher than its carrier power - but the sidebands are lower in amplitude than the carrier. And I'd not expect PS ripple voltage to act as if it were a sine wave; it isn't. This will also affect its amplitude on the SA (or in FFT of the 'scope waveform). Are we having fun yet? Cortland 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: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org 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
