> On Oct 14, 2016, at 11:34 AM, Cube Central <cubecent...@gmail.com> wrote: > > Nick, thanks for your detailed reply. Would you happen to have a photo of > the "spring looking things?" I am not entirely sure I have one of those > included with the kit that came with the scope.
I don’t have a picture, but the Internet does: http://i.stack.imgur.com/PSo3N.jpg > What size of capacitor would you suggest? Well, I use mostly 0805 MLCCs on my boards, not counting the occasional polymer or electrolytic. > I happen to have the exact same dummy load that you do. I have added on a > fan for higher current/longer use. > > Thanks for the help, I look forward to trying out some of the measurements > that I've seen posted elsewhere ( such as this link: > http://www.righto.com/2012/10/a-dozen-usb-chargers-in-lab-apple-is.html ) > > Cheers! > > -Randal R. > (at CubeCentral) > > -----Original Message----- > From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Nick Sayer > via time-nuts > Sent: Friday, 14 October, 2016 12:17 > To: Discussion of precise time and frequency measurement <time-nuts@febo.com> > Subject: Re: [time-nuts] For those that insist on using switching power > supplies > > Set your scope for AC coupling. Set your scope probe for 1x rather than 10x. > Use the absolutely shortest scope grounding you can. That’s what those spring > looking things that came with it are for. I typically use the spring gizmo > and probe on an SMD cap. The ground wire with an alligator clip will just > pick up far more noise than you’ll be measuring. This is how I was able to > measure the noise and ripple of the SC189Z switcher feeding the OCXO in my > GPSDO. I got measurements of ~4 mV P-P that way. Be careful you don’t get the > probe and ground reversed - your scope won’t likely have an isolated ground > from your DUT and that would therefore be bad. > > You’re going to want to check the supply’s performance under load. For that, > you’ll may want to get yourself a dummy load. I got one from Tindie for > testing my Pi Power design: > https://www.tindie.com/products/arachnidlabs/reload-2/ > > > >> On Oct 14, 2016, at 11:00 AM, Cube Central <cubecent...@gmail.com> wrote: >> >> How would one go about testing power supplies and seeing how noisy they are? >> I have the standard suite of tools, an oscilloscope and a little >> (dangerous) know-how. I am just not sure what to look for or how to safely >> hook it up to test. >> >> Thanks in advance for any tips! >> >> -Randal R. >> (at CubeCentral) >> >> -----Original Message----- >> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Chris >> Albertson >> Sent: Friday, 14 October, 2016 02:29 >> To: Discussion of precise time and frequency measurement >> <time-nuts@febo.com> >> Subject: Re: [time-nuts] For those that insist on using switching >> power supplies >> >> On Thu, Oct 13, 2016 at 6:05 AM, Van Horn, David >> <david.vanh...@backcountryaccess.com> wrote: >>> To be fair here, phone chargers have almost no requirement to be quiet >>> other than conducted and radiated emissions limits. >>> It's charging a battery. >> >> Not only that but, the 5 volts comping out of the larger is almost >> certainly the input to another DC/DC power supply and NOT used directly. >> You can't charge a Lithium battery with the 5 volts the charger outputs. >> >> If you don't know about LiPo batteries, they need a constant current power >> source and then as they get close to charged the charger switches to >> constant voltage (VERY roughly) at about 4V per cell. >> >> I have a project right here on my desk as I type. I'm using the output of a >> generic USB hub. The circuit is a cap from 5V to GND and >> then a low dropout regulator to get 3.3 volts. I don't care to much >> if there is huge ripple on the 5.0 volts coming in as long as it stays above >> the LDO limit. >> >> Also it looks like they tested the USB chargers with no load. A typical >> load might have a say, 0.01uf cap to short the noise to ground. So in use >> the power might be better? >> >> It was no surprise the counterfeit chargers were horrible. The >> manufacturers are by definition of "counterfeit" being dishonest slim balls. >> Why would he care about anything other then that he can fool >> some people into buying his product. There are third party chargers >> that are not trying to copy a well known brand, these are usually much >> better >> >> >> -- >> >> Chris Albertson >> Redondo Beach, California >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
