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Intelligent System to Measure Liquid Height by Ultrasonic Based on Single-chip Microcomputer

CAO Jian-hai~1,LU Chang-hou~1,HAN Xu-dong~2(1.School of Mechanical Engineering,Shandong University,Ji'nan 250061,China;2.School of Information Science and Engineering,Shandong University,Ji'nan 250015,China)  
The principles and the frame of the system to measure liquid height by ultrasonic is presented.The circuit of exciting ultrasonic and sampling environmental temperature is detailed.The sightless area and the time measure error are removed basically by an effective method of transforming received signal.Firstly,the received signal is magnified by the method of STC(Sensitivity Time Control).Secondly,a linear encircling demodulation is used on the magnified signal.Finally,the desired signal is attained by the method of differential circuit and zero-cross demodulation.At the same time,temperature error is compensated.Adopt modular programming and develop successfully this system on a single-chip microcomputer.The measure results show that the system can obtain higher precision and better adaptability.
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