A ultrasonic distance-measuring system with transmitting and receiving sensor is designed.In hardware design

W77E58 is chosen as micro-processor to improve the resolving power of measuring time.The problem of increase of system measuring error caused by too weak echo wave signal in-long-distannce measurement is solved by automatic gain control（AGC）circuits.The response time of system hardware and the distance between piezoelectric material of ultrasonic sensor and sensor surface are considered in software design to correct the measuring result.The experimental results show that it has high precision

good repeatability and high reliability.