The increasing interest in their meter departments which is being shown by the managements of electricity supply undertakings is a matter for congratulation and is resulting in a very encouraging improvement in meter-engineering practice.In this paper testing-equipment design is discussed and the conclusion is drawn that primary resistance-regulated current-loading transformers can be satisfactorily employed. Good electrical performance is considered to be the most important feature of a single-phase meter; and a new method of testing to certify this feature is outlined. The merit of calibrating to special limits of error is discussed, together with routine methods of testing single-phase and polyphase meters.