IEC 60051-4:2018 applies to direct acting indicating analogue frequency meters of the following types:
•    pointer-type frequency meters (as defined in 3.2.11 of IEC 60051-1:2016),
•    vibrating-reed frequency meters (as defined in 3.2.12 of IEC 60051-1:2016).
IEC 60051-4:2018 also applies to non-interchangeable accessories (as defined in 3.1.23 of IEC 60051-1:2016) used with frequency meters.
IEC 60051-4:2018 cancels and replaces the fourth edition published in 1984. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous edition:
a) updating of content in line with new editions of IEC 60051-1 and IEC 60051-9,
b) addition of Annex A to specify the nonconformity classification of test items.
IEC 60051-4:2018  is to be used in conjunction with IEC 60051-1:2016.