Differential probe for offline PFC'd PSU

[Faringdon]

Thanks yes i must admit those Telonic prices are  a lot better than some others.

[Faringdon]

Thanks for these great answers, and thanks jc101  i now have the micsig diff probe and its very good.
Of course, when i probe the current sense resistor (burden) of my PFC it is just full of pickup as these diff probes have each probe on separate lead......so i think i will still need to buy an isolation transformer so that i can use a  home-brew coaxial probe to look at it without so much common mode junk in the way.

Alternatively i woudl like to take the back off the scope, measure the DC output of the offline SMPS... disconnect it, then feed in a isolated DC supply and then i have a floating scope.
Its a Tenma 72-8225

[nctnico]

Thanks for these great answers, and thanks jc101  i now have the micsig diff probe and its very good.
Of course, when i probe the current sense resistor (burden) of my PFC it is just full of pickup as these diff probes have each probe on separate lead......so i think i will still need to buy an isolation transformer so that i can use a  home-brew coaxial probe to look at it without so much common mode junk in the way.

Alternatively i woudl like to take the back off the scope, measure the DC output of the offline SMPS... disconnect it, then feed in a isolated DC supply and then i have a floating scope.
Its a Tenma 72-8225

Don't do that (unless you have a death wish). Buy a current probe instead!

[Faringdon]

Thanks, the output current of the secondary  is just 100mA peak, so i dont think i can buy current probe to see that small?

[jc101]

The current probes from Teleonic will see that, I was using them down to 15ma just fine. I can look the model number out tomorrow.

[nctnico]

Thanks, the output current of the secondary  is just 100mA peak, so i dont think i can buy current probe to see that small?

No problem at all. Alternatively you can use a current transformer in series with the current sense resistor. Wurth has several nice current transformers that work up to several MHz.