This part of IEC 60051 applies to direct acting indicating phase meters, power factor meters and synchroscopes having an analogue display. 
This document also applies to non-interchangeable accessories (as defined in 3.1.23 of 
IEC 60051-1:2016) used with phase meters, power factor meters and synchroscopes. 
This document also applies to a phase meter or power factor meter whose scale marks do not correspond directly to its electrical input quantity, provided that the relationship between them is known.dition 5.0 2017-12 INTERNATIONAL STANDARD NORME INTERNATIONALE Direct acting indicating analogue electrical measuring instruments and their accessories – Part 5: Special requirements for phase meters, power factor meters and synchroscopes Appareils mesureurs électriques indicateurs analogiques à action directe et leurs accessoires – Partie 5: Exigences particulières pour les phasemètres, les appareils de mesure de facteur de puissance et les synchronoscopes IEC 60051-5: