The task is to undertake a research on a control system applied to ultrasound instrument which performs the functions as follows . firstly , it can output a pwm wave which duty ( 0 ~ 100 % ) and frequency ( 0 . 1 - 10hz ) are adjustable . secondly , it can output a switch and timing signal . thirdly , it can detect the frequency of signal generator ( 20k ~ 100khz ) 本课题任务是进行一个超声仪的控制系统的研究,主要实现以下技术指标:输出占空比( 0 100 )和频率( 0 . 1 10hz )可调的pwm信号;产生可控定时的开关量信号;检测信号源的频率值( 20k 100khz ) ;在pc机监控软件界面和控制器液晶显示屏上显示其工作状态和参数。