Rigol 2072a Oscilloscope - 230V Mains - Switching Power Supply Probing

[pantelei4]

I use Rigol 2072a + Micsig DP10013 for measurements in hot connections. 
Oscillograms of 1 MHz meander, amplitude 5 V, band limitation 100 MHz
- DP10013 delay around 5ns (blue 10X, yellow 50X)
- noise 50X
- noise 500X

[David Hess]

300 volts RMS is 425 volts peak so there should be no problem.  Rigol's lack of frequency derating makes this specification fuzzy so I would not trust it; it could be better or worse so take your chances.

Note that a typical x100 probe will *not* protect the oscilloscope from excessive DC voltage when AC coupling is used.  These probes need to be used with DC coupling at high voltages.

[VooDust]

Note that a typical x100 probe will *not* protect the oscilloscope from excessive DC voltage when AC coupling is used. 

How so?

[Performa01]

Note that a typical x100 probe will *not* protect the oscilloscope from excessive DC voltage when AC coupling is used. 

How so?

The typical x100 probe is (simplified) just a 99 meg series resistor with a cpacitor across.

So, if the scope input is open circuit for DC in AC-coupled mode, the full voltage present at the probe tip will charge the internal DC-blocking capacitor of the scope up to the full voltage within seconds. Since the capacitor is unlikely to be rated for much more than 400V, it might not survive an input voltage of e.g. 1000V, but if it does (not unlikely) it will hold some substantial amount of energy when fully charged. If you connect some low impedance source to the scope input after this, the input capacitance will discharge into the input buffer of the scope, where some parts might not be too hapy seeing voltages much higher than 400V.

Thankfully, this is only a problem with certain (mostly obsolete) designs.

The vast majority of mdern general purpose oscilloscopes with high impedance inputs have a different input architecture and AC-coupling is solved differently.
As a consequence, most modern GP DSOs provide a constant input impedance, regardless of the input coupling.

One can easily check this with a DMM: can you still measure the 1 meg ohms input impedance in AC coupled input mode? If so, you are safe to use the x100 HV-probe without further considerations.