| The ultrasonic calorimeter is a device for measuring heat.In twenty-first Century,the demand for the ultrasonic heat meter was expanding.But there are many deficiencies in the ultrasonic heat meter measurement,such as jet lag filter,small flow measurement is not stable,in order to solve these problems,this paper presents a design of ultrasonic heat meter,ultrasonic transmission mode using U path,choose MSP430 series microcontroller,temperature,time measurement chip selection TDC-GP22,aiming at the shortage of ultrasonic the heat meter has done the following research.Firstly,the extraction of TDOA signals is introduced in detail.The Calman filter algorithm is used to filter the time difference,and the data is simulated with MATLAB.The data is obtained through the experiment.After the simulation is completed,the time difference can be filtered by the Calman filter algorithm.Then it introduces the application of arithmetic average algorithm in the time difference filtering,compares the Calman filter algorithm with the arithmetic average algorithm.Through the experiment comparison,it is found that the error of the ultrasonic heat meter which downloads the Calman filter algorithm is stable,and the precision is high.An ultrasonic calorimeter with arithmetic average algorithm can be downloaded to meet the requirements of the basic two level table.The error is within the allowable range,but the floats are larger.The ultrasonic heat meter designed in this paper uses the path form of U type ultrasonic.The factors affecting the time difference measurement have been analyzed.Because of the influence of various factors,the calculation of the flow can not be calculated by the formula or theory time difference,but the relation curve of the time difference and the flow amount should be drawn.Temperature has great influence on the measurement of flow rate,and there are different curves at different temperatures.In this design,traffic is divided into large flow area and low flow area.The curves of the time difference and the flow point are fitted by the least square method at 25,50 and three temperatures,and the curves of the large flow area and the small flow area are connected together.Through the MATLAB simulation,the curves and curves of the time difference and flow rate under each temperature are obtained,and the surfacecurves of temperature,time difference and flow rate are obtained.In the end,two heat meters are used to do experiments.The program is downloaded with a traditional time difference flow,and the other is the sequential least square method to improve the time difference and flow rate.The experiment shows that the calorimeter with the traditional time difference fitting method meets the requirements of the two level table,but the small flow point is unstable and the error fluctuate.The method of least squares is used to improve the fitting method of time difference and flow.It shows that the least square method can improve the fitting time difference and flow rate,and can improve the instability of the flow point in the calorimeter. |
