Monitor apparatus can measure valid value of three phase voltage and current , power factor , three phase disequilibrium , instant flecker of short time and harmonic without twenty , degree and harmonic distortion total . the paper are laid on the following . ( 1 ) master plan and function of circuit , ( 2 ) hardware design including circuit and principle of a / d conversion , phase lock , liquid crystal display and keystroke and so on , ( 3 ) design of system software including digital filtering , fft , a / d conversion and monitor interface of pc , ( 4 ) system test 监测仪能够完成包括三相电压、三相电流的有效值、功率因数、三相不平衡、电压短期闪变、以及20次内的谐波、谐波相位、谐波失真总量等的测量。论文重点介绍了以下几部分： ( 1 )电路的总体设计和功能； ( 2 )硬件设计，包括a d转换、锁相环、液晶显示和按键输入等原理和电路。 ( 3 )系统软件设计，包括a d转换、 fft 、数字滤波等程序的原理和算法以及上位机监控界面的设计； ( 4 )系统测试。
