The Reference Standard RS 2x20B is single-phase (RS 2120B) and three-phase (RS 2320B) version of precision meter for electrical power and energy measurement. The Reference Standard is designed to meet all requirements put on a reference standard in a single- and three-phase electricity meter testing and calibration systems. The Reference Standard can be set to any real or artificial mode of operation in three phase system and is capable to evaluate the individual quantities per phase and the three-phase cumulative quantities as well. Reference Standard is based on precision 24-bit A/D conversion and digital signal processing technology enabling accurate evaluation of all main and informative quantities. Beyond measurement of all kinds of power, voltage, current and phase, the meter measures the harmonic content and distortion of the input signals. The meter constant of Reference Standard generating value-proportional impulses on the frequency output is freely programmable and can be assigned to various quantities or set to generate any precise constant frequency for testing purposes. The Reference Standard RS 2320B is equipped with three fully independent differential voltage input circuits. Therefore the meter can be configured to evaluate signals on three independent channels. This feature in combination with possibility to assign the impulse outputs to any combination of the input channels enables to use the device for example in single-phase system with one channel as reference while the free channels can monitor additional information like power consumption of the current and voltage circuits or contact error in the test circuit.