Study Of Purified Water Meter Based On Ultrasonic Principle

With the development of social economy and the improvement of people’s quality of life,the demand on purified water in food production and household life is gradually increasing.As the instrument of flow measurement,purified water meter is the basis of trade settlement.At present,purified water meters mostly use mechanical sensors,which have problems such as low turn-down ratio and large start flow.So it cannot meet the requirements of flow measurement.With the advantages of small start flow,large turn-down ratio and low pressure loss,ultrasonic water meter has been widely used in medium and large diameter pipeline.However,in the measurement of purified water meter,there are the problems such as the complex flow field,the short sound path and the noises of measurement because of small pipe.So the accuracy and stability of measurement are at low level.In order to solve the above problems,a purified water meter based on ultrasonic principle is studied.Firstly,two reflective pipes of the reducing diameter with different sensors’ layout are designed.The flow characteristics inside the pipe are studied by FLUENT simulation.The rationality of the pipe models are evaluated by using hydrodynamic coefficient K and root mean square of the flow velocity.The better pipe model is obtained,and the flow experimental is verified on the experimental facility.Secondly,the software and hardware measurement system based on MSP430F449 and TDC-GP22 is designed.The system circuit includes main control circuit,time measurement circuit,signal switching circuit,echo signal processing circuit,temperature measurement circuit,power supply circuit and human-computer interaction circuit.The operation of each module function is done by interruption in the software system.So the overall power consumption of the measurement system is reduced.The software mainly include the main program,time measurement program,flow calculation program,temperature measurement program,communication program and storage program.A data filtering method based on Improved Kalman filtering is designed in order to solve the problems of transit time measurement result from the fluid disturbance noise and circuit interference.Compared with the traditional filtering method,it has fast instantaneous response ability under the condition of flow change.The optimization results are simulated and verified by simulation analysis.An measurement error correction method based on the Reynolds number is proposed.The Reynolds number is used to the nonlinear error correction model.Compared with the traditional linear interpolation correction model,the temperature and viscosity is used in the correction model.So the accuracy of measurement is more accurate.Finally,the prototype of ultrasonic purified water meter is tested.The pipeline model experiments,temperature calibration experiments and flow experiments are done.The experimental results show that the water meter has good characteristics.It meets the accuracy requirements of grade 2,and the turn-down ratio is R400.