BNC-BNC probe

[Behemot]

I am thinking about ATX PSU loader v2.0 all the time and one of the things I need to solve is taking ripple measurements. Probably the best way would be to internally connect cables directly to each rail (and ground ofc) and than end it with BNC on the loader casing. There I would connect BNC-BNC probe from O-scope. This should spare me of catching any noise from outside as the loader itself would be heavily shielded (so nothing could go inside) and using coaxial cable between loader and O-scope will prevent from catching anything from air on the way.

The question is, are there BNC-BNC 10x probes on the market? All I can find are BNC-crocodille probes. If not, I'd have to basically make my own probe. That means, using some big resistors inside and ordinary 50ohm cable for connection to O-scope. Not that it is any difficult in theory, but getting some precision may be somewhat worse using ordinary resistors and so. Buying just a probe is easier and I think it will be more accurate.

[ben7]

Re: BNC-BNC probe

It would be a much better idea to measure the ripple as close as you can to the PSU! The wires going to the load tester will have some inductance, and some resistance. If there is the right amount of inductance, you might see the ripple almost disappear, which will give you incorrect ripple voltage readings!

http://technoblogin.blogspot.com/200...tutorials.html
About two-fiths of the way down that page, the passive o'scope probes are explained. You can try making one if you want, since there is a schematic for a 10x probe in that part of the page. I sugguest using some smaller diameter coax, not the coax used for TV, that is just too clunky!

Another way to do it is to use some connectors that the probe plugs in to (a probe with the crocodile cover removed from it). I'm not sure what they are called, but I have seen them before on DC-DC converter demo boards!

[Behemot]

Re: BNC-BNC probe

I will have thick wires enough inside the load. As for going from load to O-scope, it should be almost the same as using passive probe I have now, those also have cable 1,5 meter (or so) long. Just if there was probe with BNC on both sides, I would not have to piffle inside the load with resistors and such.