High-precision Measurement Of Displacement Based On Ultrasonic & CPLD

More attention is paid to waterpower, so the project was broached. Vertical displacement of the hydroelectric generating set caused by vibration, a high precision measurement was developed.Introduced history and development of ultrasonic measurement, analyzed characters of transducer and provided equivalent circuits. Theory of measurement based on ultrasonic and some usual means were mentioned. Focused on ultrasonic echo measurement, key point which affected the precision of measurement was mentioned and the high precision measurement based on ultrasonic and complex programmable logic device was developed. Some other factor which interfered the precision of measurement were explained.Based on ultrasonic and Complex Programmable Logic Device (CPLD), a research focused on high-precision displacement measurement was developed. In this system the time information was captured by CPLD and transmitted to MCU for operating. The precision level was determined by frequency of CPLD. Therefore, high precision measurement was achieved and the theoretic precision of time-passed can reach 1μs.With the system's advantages of high precision, low cost, measurement of continuum and easy operation, the shortage of traditional measurement depended on MCU's frequency was avoided.Introduces the process of the project in theory analysis, system collectivity design, system hardware circuit design and system software circuit design. There is great innovation in this system's hardware and software design. First, rising edge trigger circuit and high speed counter were designed in CPLD to realize high precision measurement. Second, software compensation is used to improve accurateness. Third, ultrasonic velocity was compensated through temperature transducer and the precision was ensured. Combination of MCU and CPLD expands the function of the system. Patent had been applied.Project was designed with transmitting and receipting transducers. To avoid the effect of measurement which caused by the distance of two transducers, the application of a transmitting-receipting transducer in measurement was discussed.