Intelligent Ultrasonic Water Flow Meter Hardware Design And Production

The project utilized the travel time difference method to design and make thesmart water ultrasonic flowmeter which is a sub-project of Guanzhong irrigation areatransformation in Shaanxi province.Firstly the principles of ultrasonic flowmeter and signal detection were explained,and the characteristics of transducer and the flowmeter errors were analyzed in thispaper Secondly, the general design, characteristics and difficult problems of theflowmeter were described. Thirdly, the principle of the main part circuit wasintroduced, that included graphic lattice LCD display keypad with 20 keys, flashmemory, system clock with real time, two high speed communication port, calculationof flow and total flow, reliability detection of velocity and flow input/output controland error alert. Finally, the principle of the flow transmitter was mainly discussed, thatincluded transducer driver signal detection, automatic gain control (AGC), travel timemeasure and path transformation. In order to develop the measure precision andreliability the problems were emphatically dealt with as follows: (1) High speed andmore reliability CPLD instead of normal devices was designed in the transmitter, andnew logic method was utilized to make the travel time error less than 10 ns. (2) The+0.2V gate signal and signal validity detection were adopted to deve1op the reliability.(3) The system with signal peak voltage holding, A/D converter, microprocessor, D/Aconverter and voltage adjustment was introduced to realize the ultrasonic signal AGC.(4) MOSFET with high voltage and high speed was utilized in transducer driver circuit.(5) In order to decrease the influence from power and driver circuit, the power of thedigital circuit and analog circuit was isolated, and the driver circuits and receivercircuits were isolated too.The measure result indicated that the improved ultrasonic flowmeter was runningwell and was easy to be operated. Travel time error was no more than 10 ns. The erroranalysis and precision calculation showed that the flowmeter reached the designrequirement.