A non-standard but repeatable way to measure power supply noise is to use a Transmission Impairment Measuring Set (TIMS) such as the HP3945(6)A or 3551 (2)A. These were intended for use in pairs to assess analog telephone lines for data use. As well as an AF generator, frequency counter, amplifier, monitor speaker and level meter they will measure broadband noise. Being designed for POTS they will also withstand at least 50V DC at the input while measuring the noise. You can also apply internal filters if required. The last digit designates a North American (BELL) or European (CCITT) standard unit, but broadband noise is the same. They can be picked up really cheaply now (list was$3000-$5000) and make a nice compact audio test set.
Robert G8RPI. ________________________________ From: Bob Camp <[email protected]> To: 'Discussion of precise time and frequency measurement' <[email protected]> Sent: Thursday, 31 January 2013, 18:02 Subject: Re: [time-nuts] Low noise power supplies? Hi A very common way to check one is to use the HP 3561 off of the old 3048 phase noise test set. With a simple op amp based preamp you can easily get down below 3 nv / sqrt(Hz). With more exotic amps you can get well below that. Volts over a bandwidth really don't tell the story very well. In the popcorn noise region, you don't have much choice. Once you get past that PSD is very much the right way to go. For some numbers once you are out of the popcorn / flicker noise region: 1 nV / sqrt(Hz) = about as quiet as it's worth getting ever. 10 nV / sqrt(Hz) = good enough for anything you are likely to be doing 100 nV / sqrt(Hz) = noisy enough to begin to bother you in some cases 1uV / sqrt(Hz) = pretty awful. As always, it really depends on what you are doing. A microprocessor will not be bothered much at all by a relatively noisy supply. Bob -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Burt I. Weiner Sent: Thursday, January 31, 2013 12:08 PM To: [email protected] Subject: [time-nuts] Low noise power supplies? Gang, I'm following this thread with great interest, but, just for my own reference, what is considered low power supply noise? Can you give me some numbers and over what bandwidth? Thanks, Burt, K6OQK > <[email protected]> >Subject: Re: [time-nuts] Low noise power supplies? > > >Hi > >To answer the original question - Power Design makes some pretty quiet bench >supplies. If you are doing low noise testing, batteries often will let you >get rid of one more ground loop. Even well built power supplies are not as >well line isolated as a battery. > >Bob Burt I. Weiner Associates Broadcast Technical Services Glendale, California U.S.A. [email protected] www.biwa.cc K6OQK _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
