The Research And Realization Of Liquid Level Measurement System Based On 485-CAN Bus

As the development of liquid level measurement technology,liquid level measurement system with direct digital signal output has become a major trend,so bus technology was gradually introduced to the liquid level measurement system. Based on the RS485 and CAN bus,research of their application in three different liquid level detection methods are conducted in this article.In this paper, MEMS (Micro Electro Mechanical Systems) pressure sensor combined with the bus technology application in liquid level measurement is researched,a design proposal to extend the range of one liquid level measurement system that use hall sensor is proposed,and a new method of liquid level measurement by capacitive grating encoded transducer is proposed.Then take the liquid level measurement system based on capacitive grating encoded transducer as an example,a detailed design proposal is given.The design proposal has certain universality, which could apply to relative liquid level measurement system or data acquisition system.First,the principle of pressure sensor to measure liquid level is researched,based on this principle and combined with the characteristics of SCP1000 MEMS pressure sensor,a liquid level measurement system using the RS485 bus to acquisition data is designed.Then the performance of the system is tested,and the test result is analyzed.Second,the principle of hall switch sensor is analyzed.On this basis,comparative study of two typical application in liquid level measurement is carried on. Combined with the two bus technologies introduced above,a solution can extend the range of hall-type liquid level measurement system with digital signal output is proposed.Third,with the basic theory of the capacity method measure liquid level for foundation,the advantages and disadvantages of concentric column capacitive liquid level transducer is analyzed.On this basis,a method using capacitive grating encoded transducer to measure liquid level is proposed. Based on this method, the hardware and software of the liquid level measuring system based on 485-CAN bus are introduced in detail. The system hardware circuit includes modules of voltage regulator, communication, capacitance detection and man-machine interface. The software introduces the design processes of the main program, the programs of capacitance detection module and bus communication.The feasibility tests of the liquid level measurement system based on capacitive grating encoded transducer are carried out in the end. The oscillograms are obtained by process of the original signals in the Labview platform. The filtering effects and the effects of the capacitance jump detection can be drawn from the oscillograms. The system can measure the liquid level under specific conditions.