User`s guide

Remarks
Autorange thresholds:
Down range at: <10% of range
Up range at: >120% of range
With autoranging enabled, the instrument selects the appropriate range
based on the input signal detected.
The ONCE parameter performs an immediate autorange, and then sets
autoranging to OFF. (Thus, the query returns "0".)
Selecting a discrete range (see [SENSe:]CURRent:AC:RANGe command)
will disable autoranging.
The instrument enables autoranging after a Factory Reset (*RST
command) or an Instrument Preset (SYSTem:PRESet command).