Research On Small Flow Ultrasonic Water Meter

Most of the traditional water meter adopts mechanical measuring method, but the accuracy is low, and it has a large pressure loss. Ultrasonic flowmeter does not have special requirement for its fluid. Its structure is simple, and it can realize automatic measurement and the flow of information management. Thus, it has been received wide attention in the field of flow measurement.In the design, the ultrasonic flowmeter is used for small water flow. The design is focused on solving measurement accuracy and measurement stability of small ultrasonic flow meter, etc. The ultrasonic flow device is made after referring to large amounts of data. We test the working characteristics which includes frequency and consistency of ultrasonic transducer and the way of ultrasonic transmission. Use the sensor PT1000to measure the temperature of water, so it can give the temperature compensation to improve the measurement accuracy. After comparing tube section mechanical structure and different installation methods, adopt the measuring principle of the time difference method in this design. Depending on the features of small diameter flow measurement and the tube, transducer installed uses the linear mode.Flow measurement uses a dedicated chip to measure ultrasonic propagation time measurement in the pipe section downstream, upstream time difference. The control unit selects16bits MCU with low consumption. By choosing a proper working mode, make full use of this chip with hardware, multiplier function, can effectively improve the work efficiency and reduce power consumption.For the characteristics of small diameter flow, make the appropriate design that includes sending and receiving switching circuit, the reception signal processing circuit and so on. In the received signal processing, two methods are adopted. They are thresholding and threshold with zero-crossing combined. After extensive testing, the results show that threshold with zero-crossing combined can get better effect. While the comparison of the measurement results, select the measurement accuracy and stability of the circuit which are better in terms of hardware. Introducing valve management, LED, mercury switches and other functional modules, make the ultrasonic meter function more perfect. And the communicate use wireless module CC1100.In software design, the design introduced modular and state machine design, so that each module is thinking more clearly, easily cutting, transplanting, therefore we can achieve the purpose of ahigh cohesion and low coupling between the module and the module. After each test of each module, integrate them. Use the thought of state machine to program, to make the program switch in the different module, which effectively improves the working efficiency. The article gives the program flow and partial state transition tables of state machine design in the software design module.In terms of algorithms, data processing uses sliding mean filter algorithm to increase the stability of the flow measurement. This design also explores the application of wavelet algorithm in terms of ultrasonic flowmeter, uses wave let de-noising method, selects the appropriate wavelets and wavelet threshold through MATLAB simulation, reached the purpose of noise reduction threshold.