由随机函数产生0~5V电压值，电压采样时间从0开始，每隔500ms采集一个点，共采集40个点（保留2位小数）。求显示电压随时间变化的曲线，并且把测量的电压存为表格文件。-0 ~ 5V voltage value generated by the random function, voltage sampling time　0 every 500ms capture a point, were collected 40 points (2 decimal places). Demand shows the voltage versus time curve and the measured voltage saved as a spreadsheet file.