The Research Of3-D Flow Sensor’s Signal Conditioning Circuit

With the gradual development of marine science, for the sensors using in theocean development nowadys, it required high performance. Velocity of flow–as animportant performance for the ocean measurement, the accuracy was demandedhighly. So the high-performance flow sensor was needed. The research was a partof the National Natural Science Foundation “The research of the three-D seacurrent sensor which can measure the upward flow”(NO.41076061) in this paper,aiming at the signal conditioning circuit of the three-D sea current sensor.Firstly, it described the weak signal detection, conditioning circuit and theoperational principle flow sensor in this paper; Secondly, for the signalconditioning circuit its main work was the detection of the weak signal, for thesignal was always weak and easily to be interfered, the high gain was need toconsidered in the designing process, the design plan of the amplify circuit wasproposed, and through analyze the multistage amplifier, getting the influence ofevery part to the whole circuit. According to the analysis of the different functionof the pre-amplifier and the second amplifier, the amplify circuit was designed.Thirdly, the analog signal was interfered easier, so the analog signal should betranslated to the digital signal by using the analog to digital converter. The morecomplicated the analog circuit is, the more interfere would be introduced, so theanalog circuit should be easier and a high performance AD converter was needed.24bit AD7714was used in this paper, and the circuit was designed. The weaksignal can be detected effectively and also reduce the demand of the analog amplifycircuit, the circuit would be easier and the little interference would be introduced.Finally, because the sensor was used in the ocean, it required long communicationdistance, RS485serial communication was adopted, and at the port of the PCRS485to RS232converter was used by communicating with the computer. In thecomputer, a display interface was built by the LabView for observing the change ofthe amplitude and the wave in real time.