The material submitted for the 2020 reinstatement of Working Group 120 is the basis for this updated version. To provide general guidelines intended to assist nonelectrical engineers and technicians involved in quality control, acceptance, and prototype testing where electrical instrumentation is the main tool for measuring, observing, or recording physical quantities is the basic approach for the new organization. The contributors strived to maintain the relevant and important knowledge that was previously carefully collected and update this as appropriate.

This guide relates to measurements of power, energy, voltage, and current in dc or ac power systems. The guide does not deal with measurements of resistance or temperature that may be of use in determining the performance characteristics of electric machinery.

The purpose of this guide is to give guidance for the measurement of electric quantities whose values are commonly needed in determining the performance of electric power systems. The choice of the measurement method and instruments to be used depends on the nature of the circuit and the purpose of the measurement.