Ultrasonic Heat Meter With High Accurate Based On Wireless Network

According to the request of developing economy society in our country, the system of heating charge will gradually transit to the thermal energy measurement charge. The existing calorimeter mainly use the measuring technical of the traditional water meter, because of low measurement accuracy, short life circle, short stand-by time and no network communication, the kind of calorimeter cannot satisfy the request of accuracy and reliability to the thermal energy measurement and remote controlling.At first, the background of study, significance and current study situation both at home and abroad about ultrasonic heat meter are introduced. And the difficult problems urgently to be solved at present are analyzed deeply.A high accuracy ultrasonic heat meter based on transit time difference method is studied, and the function of network communication is extended also. The work principle and composition of ultrasonic heat meter are systematically analyzed; it also researches water flow measurement principles of time different ultrasonic flow and temperature measurement principle during capacitor charge and discharge as well as their respective methods of achievement. The two key modules of flow measurement and temperature test of heat meters are reunified to the very problem of time measurement. The high accuracy time measurement is gained by help of a high accuracy timing chip TDC-GP2; the communicating chip CC2430 built-in ZigBee protocol and based concept of system-on-chip is used to realize network communications. The system makes fully use selected time-chip and communication-chip, which has advantages of full function and low power consumption.An automatic gain control circuit used in ultrasonic flow measurement system is proposed in this paper. A mathematical model of the AGC loop is established, the variable gain and settling time of the AGC circuit is analyzed and calculated based on mathematical model. And then the AGC circuit is designed, the influence of ultrasonic flow measurement calculation and performance is also analyzed. Experiment proved that the method can improve system performance indeed.In order to improve the processing accuracy of echo signal, the flow measurements based on ultrasonic time-of-flight estimation is dealt with in the paper. Proposing the use of Unscented Kalman Filter (UKF), acquiring echo signal envelope, and then using the parameters of the envelope as the processed state vector to deal with ultrasonic echo signals. The paper improves the operation of UKF process based on the characteristics of flow measurement, and given the condition of beginning and end UKF iteration. Finally, some stimulus is given to simulate the performance of UKF and its convergence rate, which assess its reliability, effectiveness.The heat coefficient K is amended based on the principle and calculation method of heat metering, and then the deviation of flow measurement is analyzed in this paper. And then, the ultrasonic transmitting, receiving and amplifying circuit are designed, and the design scheme of adding the time-to-digital converter is put forward in order to enhance the accuracy of heat meter.In order to satisfy the demand of long time to work independently, the selected low power consumption chips and the circuit is designed as low as possible. The new solution is proposed to solve this problem.