IEC 62057-1:2023 applies to stationary meter test units (MTUs) permanently installed in laboratories, used for testing and calibration of electricity meters, in particular for their type test, acceptance test and verification test. It covers the requirements for automatic MTUs for indoor laboratory application and applies to newly manufactured MTUs to test electricity meters on 50 Hz or 60 Hz networks with an AC voltage up to 600 V (phase to neutral). If meters are intended for system voltages not specified in this document, special requirements are agreed between the manufacturer and the purchaser. This document also defines the kind of tests to perform as type tests / routine tests / acceptance tests and commissioning tests for MTUs. It does not apply to: • portable reference meters and portable sources; • electricity meters; • data interfaces to the meter and test procedures of data interface; • transformer operated MTUs; • personal computers supplied together with the MTU.