A DSP-based watthour meter

A high-accuracy, three-phase electronic watthour meter, implemented in a 3.5- mu m double-poly CMOS technology, is described. It receives inputs from voltage and current sensors, measures both real and reactive power, and outputs pulses whose rate is proportional to energy flow. The meter is accurate to 0.3% of reading over 3.5 decades. A block diagram is presented, and the device functions are described. The DSP (digital signal processor) is developed as a macro cell with customized ROM/RAM. It has a 16-bit data path which can shift N bits and accumulate in one clock cycle. Both scalar and variable multiplications are possible.<>