Dimensions of the EQ 0307 are 72x72 mm and it has 90 degree dial. The instrument operates on fast sampling method of input quantities (current and voltage) on all three phases. Microprocessor calculates active, apparent power (EQ) from the input data. Meter comprises current transformers, voltage dividers, microcontroller and power supply unit. Power supply is provided from L1 and N (4u, 4b, 1b) or L1 and L2 (3u, 3b) voltage terminals. Measuring system with moving coil is connected to the microcontroller. The instrument scale is calibrated on W, var or cosφ, considering ratios of current and voltage transformers. Long term stability is achived by storing setup and calibration constants into microcontroller. Easy and fast scale excange is posible because of the meter’s costruction.