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Old 11-24-2016
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crmaris crmaris is offline
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when you measure ripple the most important is to provide a clean source! If not then what ever you use, differential or normal probe, will be rendered useless.

Also all professional grade breakout boards have the decoupling caps near to the scope's connection board, as itelectro mentions.

For me differential probes aren't needed. I have a good pair of those which I only use when i want to measure really high voltages or when I want to reassure that my scope won't break. A good and fast scope is what you need (not so fast though unless you want to measure transient response). Even a plain stingray scope with its joke bandwidth catches the same amount of ripple that an ultra expensive scope reports.

However there is a trick here. Some PSUs although show normal ripple, once pushed periodically they have spikes. In order to catch those spikes you need to monitor for quite a long time and use a trigger action or just log in real time the scopes output and have software report those spikes (I use the second method since I am a software/control freak).

In addition, if you put extra sensors inside the PSU you should be extra careful because those sensors can increase ripple in some cases! Learned this the hard way.

Finally, everything that is connected to the PSU, including the scope, has also to be fed by a totally different line since in some cases even a Chroma source isn't enough to provide a clean input to the DUT.
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