Help! How to choose a proper current probe for my oscilloscope?

[ali6x944]

Are you measuring the mains side, the output side, or both?  They require very different tools.

I'm measuring in both

[ali6x944]

But I'm still confused, will it measure pulsating dc or off setted waveforms as it similar to ac but without going negative?

[David Hess]

Hi everyone,
I was doing some repairs on a cuple of SMPS and other ac appliances and I needed a way to measure current and voltage, the way was using a 5w 1 resistor and two probes across the resistor to measure the voltage potential, well it is fine  if I want to measure power delivered to a load but not to great for my application so I want an expert recomendation on this subject...

If you want to measure the high speed waveforms of a SMPS, then you need something like the mentioned Tektronix P6021.  Know however that the P6021 is an AC only probe and will saturate at a pretty low DC level; it can measure drive waveforms where the average DC current is low and the current through capacitors to make ripple current measurements but it cannot measure inductor current except at low average DC levels.

For DC measurements you need an AC/DC probe like a Tektronix A6302/AM503 and those are more expensive.  A Pintek PA-699 could work but its 1.5 MHz bandwidth is pretty low for this type of application and new they are still about $800.  Someone else in the forum no doubt knows about other modern AC/DC oscilloscope current probes but none of them are cheap.

A better option may be to continue using a shunt resistor and high voltage differential probe.  I have a P6021 AC only probe so my usual solution for DC measurements when doing design work is to include a fast discrete current to voltage output which uses a low resistance current shunt as part of the circuit where I want to make a measurement.