When is Isolated Differential Probe needed?

differential probe

Hello, Is it true that if i want to measure signals of more than 50 to 60V per microsecond rising edge (eg drain node of switching FET in an SMPS) then i MUST use an Isolated Differential Probe ?

Also, supposing i have this Isolated Differential Probe fitted to my scope.........>

https://www.conrad.se/?ref=tradedbl...nrad.se/?ref=kelkoo&article=121722&ref=kelkoo

Diff Probe USER MANUAL
**broken link removed**

...>....will it be OK to measure simple non-floating voltages referenced to earth ?ground

differentiele probe

Testec differential probe and similar are actually not isolated probes rather than differential amplifiers with good common mode rejection. The differential amplifier is still referenced to the output (oscilloscope) ground and uses compensated resistive voltage dividers to achieve the common mode and differential voltage range.

Probes with true optical isolation are also manufactured, but only used for special purposes as HV measurements. By state of the art, you'll find now battery operated and WLAN remote controlled oscilloscopes in HV experiments.

To my opinion, the said differential probes are a must for most power electronics measurements, although they still suffer from common interferences in fast switching circuits. Keeping this limitations in mind, they allow a live view at power electronics.

See a Testec probe PCB detail view for reference: