so if I understand correctly, you can measure the 230rsm network voltage by setting the probes to 1x10. The danger comes only if the ground probe is wrong. Correct?
perhaps for a beginner like me better not to risk...
![Huh? ???](https://www.eevblog.com/forum/Smileys/default/huh.gif)
You have been warned by some very experienced people not to measure mains voltage. That somebody gave you a procedure that MIGHT work (I didn't check it), it comes with a certain risk of having exposed voltages where you don't want them. Like on the BNC connectors... As soon as you see the phrase 'float the scope', run away fast! The term "isolation transformer" isn't much better. Please don't do it!
Even if you saw all the trash in the world on the mains, you a) couldn't do anything about it and b) prove that it caused any harm. There is just no valid reason for probing mains at your level of experience. I say that because I have been fooling around with this stuff for over 60 years and I don't have a reason for doing it and never have. The only good thing to come from probing mains is to increase the sales of scopes.
Once you learn about differential measurements and differential probes then, given adequate Personal Protective Equipment (PPE), go for it! Until then, stay on the low voltage side of power sources. Even then, you have to know what you're doing before you hook up that ground lead.
I'm not even a fan of the A-B method of taking a differential measurement with 2 channels. In this case, both ground clips are physically removed from the probes and two probes are used to take the measurement. You can read up on differential measurements but I still wouldn't recommend it.
Which brings up another problem. Even if the probes are rated for the voltage, the scope probably isn't. So we use 10x probes. But that's a trap when it is just a slide switch selecting 1x or 10x. It is inevitable that Murphy will have the switch in the wrong position. If you need 10x probes, buy fixed 10x probes with no switches. Probe Master makes some as does every other probe manufacturer.
Please stay away from mains!