SMPS output ripple voltage measurement with 10:1 scope probe is best?

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treez

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https://www.edaboard.com/threads/254629/
…surely the above thread is incorrect…..SMPS output ripple should best be measured with a x10 scope probe, and not a piece of coaxial cable which will be a 1:1 probe and will overly capacitively load the high frequency bit of the measured value?
All that is needed is to remove the “tail” at the end of the probe and measure the ripple via the ground “barrel” of the probe and the tip of the probe...do you agree?
 

So long as the other end of the cable is properly terminated, it will only present a real impedance to the output, and a good cable can have extremely wide bandwidth. A DC blocking cap can also be used to protect the scope/SA. This method is useful for measuring EMI into the GHz range.
 
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thanks, and a properly terminated piece of coaxial cable is going to be better than a 1:1 scope probe?
 

My personal experience measuring ripple, the #1 cause of incorrect readings is a long probe grounding wire and/or ground loops.
When I worked in SMPS design we had a wide BW diff probe made by HP for the purpose.
It was expensive.
Otherwise you can use an AC coupled cable and a high quality termination. The BW can be hundreds of MHz that way.
 
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