Research On Ultrasonic Level Meter Based On Mobile Communication Network

As a representative of the non-contact measurement instruments, ultrasoniclevel meter has the merits of low cost, long life and high reliability. So it has beenwidely used in the field of industrial process control. Remote monitoring system hasbecome the direction in the development of these instruments while modernizationof production puts forward more and more requirements to auto-measurementtechnology. Previous monitoring system mostly adopts the cable network. And a fewof them have the function of SMS notification or RF communication. However, theinherent defects of these transmission methods restrict the potential applications ofthe instruments greatly. In recent years, with the rapid development ofcommunication technology, the application advantages of mobile communicationnetwork become apparent gradually in the field of remote wireless monitoring.In this paper, the research status at home and abroad of ultrasonic levelmeasurement technology and monitoring system was introduced firstly. And thenstarting from wave equation, the transmission characteristics of ultrasound werestudied. At the same time, the advantage and disadvantage of the time-of-flight (ToF)detection method was analyzed. A fast processing plan was put forward to deal withthe shortcomings of traditional way by synchronal compensation of temperature andhumidity. After that, RF network and mobile communication technology were usedin level meter. Multi-level network architecture which could expand not only thedistance of wireless communication but also network capacity was established bymeasurement nodes, coordinators, terminal auxiliary node and the server.Measurement nodes were responsible for data acquisition and RF network coverage.And coordinator was actually the gateway to connect with RF network and GPRSnetwork. In order to avoid the conflict of multi-point communication, the mechanismof hand-shake was used in CSMA/CA protocol. According to the hardware featuresof nRF905, frequency hopping strategy was enabled in data channel to alleviate theeffects of outside interference. Through automatic switch of GPRS/SMS, the packetloss rate nearly reduced by50%. At the same time, the continuity of data storage wasensured by adding terminal auxiliary node in the network topology. The serversoftware adopted the structure of B/S (Browser/Server) to improve the quality ofwebsite access. Web page was developed by JSP technology. The data received fromRF network was managed uniformly by SQL Server2005. Users who were granted with certain authorities can get the information timely when they visit the website.Through a variety of comparison tests in different conditions, the results showthat the system runs stably with high accuracy. It can meet the requirements of levelmeasurement in middle and small tanks while the response rate is better thanexpected. The instrument can be not only used alone, but also applied cooperativelyon network. To a certain extent, it can adapt to complicated circumstance. Therefore,this paper can provide some references and directions for future research in thisfield.