Scope probe 1x vs 10x setting, when does it matter?

[mark_ee_qc]

Finally got a used Rigol DS1052E. Probe has a 1x/10x switch. Nobody explained when to use which.

What I gathered:

• 10x: divides signal by 10, but higher bandwidth + less circuit loading
• 1x: full amplitude, but limited bandwidth + loads the circuit

So for I2C at 400kHz, 10x always? For low-freq low-amplitude sensor signals, 1x to see small values?

Also: scope has to know probe setting (menu) or math is wrong. Missed this, read 10x voltage as 1x = confused for an hour.

Scope users: rule of thumb for probe setting? Just leave 10x always?