The Working Standard is an accurate single-phase (WS 2120) and three-phase (WS 2320) meter for electrical power and energy measurement dedicated for on-site testing of all type of meters (static & electromechanical meters). The device equipped with universal optical scanner eventually with cable for SO output pulses and with fixing system for all kind of meters enables impulses scanning from measured meters. Manual snap switch simulates pulses from the measured meter, too. The current inputs are equipped with interchangeable current transducer, type CT (1 mA - 20 A), current clamps, type CC (1 mА -120 A, resp. 1 mА - 240 А) or current probes, type FCP type (0,2 - 6000 А). Measured and cumulative results are displayed on coloured LCD phase by phase. It is possible to display them in a form of phasor diagram at the same time or in the form of oscilloscopic waveforms. The device measures higher harmonics and it is possible to display them in a table or graphical form. Measured and calculated results are stored in high capacity flash memory. It is possible to transfer and process these results in PC under Windows compatible software. The software and device menu are implemented in regional languages. The portable printer for printing of measured results or actual content of display is an optional accessory. The device is equipped with internal rechargeable accumulators excluding it from own power consumption from tested voltage and eliminating it from degradation of measurement precision. The device is manufactured in four precision classes.