说明：  熟悉pic单片机的 AD转换 软件思路：选择RAO做为模拟输入通道； 连续转换4次再求平均值做为转换结果 最后结构只取低8位 结果送数码管的低3位显示
(Familiar with the pic of the AD conversion software Singlechip thinking: Select analog input channel for RAO consecutive conversions on average 4 times longer for the results of the final structure as a conversion, only the low 8-bit digital tube to send the results of the low 3 shows)