说明：  利用C8051F020系统板，设计一个转速测量仪器。利用反射式光电传感器设计测量系统，对转速进行测量。当传感器对准风扇时，叶片上的白色反光，黑色不反光，利用这个原理，进行转速测量。并在LCD上显示转速值，保证误差在1Hz以内。
(Use C8051F020 system board, design a speed measurement instruments. The use of reflective photoelectric sensors designed to measure the system, the speed measurement. When the sensor aligned fan, the blades on white reflective, black non-reflective, the use of this principle, the speed measurement. And the speed value displayed on the LCD, to ensure that the error in less than 1Hz.)