This part of IEC 62586 specifies functional tests and uncertainty requirements for instruments whose functions include measuring@ recording@ and possibly monitoring power quality parameters in power supply systems@ and whose measuring methods (class A or class S) are defined in IEC 61000-4-30. This document applies to power quality instruments complying with IEC 62586-1. This document can also be referred to by other product standards (e.g. digital fault recorders@ revenue meters@ MV or HV protection relays) specifying devices embedding class A or class S power quality functions according to IEC 61000-4-30. These requirements are applicable in single-@ dual- (split phase) and 3-phase AC power supply systems at 50 Hz or 60 Hz. It is not the intent of this document to address user interface or topics unrelated to device measurement performance. The document does not cover post-processing and interpretation of the data@ for example with dedicated software