RIGOL DM3068 - Manual (Page 156)

RIGOL Chapter 6 Specifications
User’s Guide for DM3068 6-10
Appling >300 Vrms (or >5 Arms) will cause self-heating in signal-conditioning components and the errors are included in the instrument specifications.
Internal temperature changes due to self-heating may cause additional error on lower ac voltage ranges. The additional error will be less than 0.02% of
reading and will generally dissipate within a few minutes.