Since I last wrote to you guys, we varied the input voltage to the entire camera...which changes the duty cycle/switching frequency of the main DC/DC converters in the camera. This changed the visible noise profile on the display...seems as though we should take a look at the DC/DC converters.
I have a couple of tidbits to answer John's reply/questions below: Chris Maxwell John Woodgate wrote: > > But NTSC is analogue. You must D/A the digits and then add them to the > NTSC syncs. What else have you left out of your description? My reply: There is a three channel video DAC that provides the final "video-ization" of the amplified, sampled, digitized and post processed IR data. I left the DAC out of my description. John Woodgate wrote: > Could that (the snow-like noise (cbm)) be background IR emission from the surroundings My reply: Probably not. A working IR camera wouldn't see this same noise. The noise is either internally generated (probable) or it's getting on the video signal, post-processing (improbable). John Woodgate wrote: > 'Snow-like' noise probably won't have any frequency peaks other than are > generated by the NTSC waveform construction. You do know that the video > signal is, in the frequency domain, a sequence of harmonics of the field > and line frequencies, with the video information as sidebands? You are > NEVER going to see quasi-random signals in amongst all that. My reply: Point well taken. John Woodgate wrote: > I really don't advise going down that route! (performing an FFT) My reply: That's fine, I really didn't want to go through all of that hassle anyway! - 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 ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email ______________________________________________________________________
