The Research Of Ultrasonic Water Flowmeter Based On TDC-GP2

Compared with traditional water flow meter,the ultrasonic water flow meter has the advantages such as simple structure,the diameter of the range measuring tube is large.At present,the domestic ultrasonic water flow meter has some weakness such as low measurement accuracy,large time error and high power consumption.In this paper in order to overcome the weakness,a new method to design water flow meter is proposed.The new water flow meter developed based on this method can overcome the shortcomings and has the advantages of high accuracy,eliminate the noise of the problems,also implements the system of low power consumption.Firstly,the history of the development of ultrasonic flow meter,the working principle and characteristics of ultrasonic water flow meter and the development status at home and abroad are described in this paper.Secondly,based on the analysis of the measuring principle and characteristics of the various measurement methods of ultrasonic flow meter,the method of different time and Z type sensor arrangement of single channel is adopted.An ultrasonic sensor with the center frequency of 1MHz is selected.MSP430F147 MCU is used to control the TDC-GP2 time chip to output two sets of primary pulse with a range of 2.85 V,whose power is amplified by the circuit designed with power FET amplifier and transformer.The ultrasonic signal coming from the emission sensor is received by receiving sensor,whose output signal amplitude is about tens of millivolt to hundreds of millivolt.The signal is amplified by the different amplifier circuit.In order to realize the improvement of signal-to-noise ratio,lower the power consumption,a single positive power supply operational amplifier MAX4132 is selected and the midpoint voltage method is used to complete the negative signal amplification.In order to filter the noise in the circuit,a second-order band-pass filter with a center frequency of 1MHz is designed.While the different flow velocity between the two states(turbulence and turbulent flow),the amplitude of the output signal of the transducer is fluctuated,a variable gain inverting amplifier circuit is designed based on digital potentiometer and ensure the peak to peak value of signal output is 2.3V in any case.In order to generate the timing square wave accurately,a square wave generationcircuit composed of a zero crossing comparison circuit and a non zero crossing comparison circuit is designed.The time difference is measured accurately by using the MSP430F147 MCU to control the time chip TDC-GP2 and the time resolution is guaranteed.Finally,the principle and equipment of the water flow meter calibration system are briefly described,and the calibration data in the flow calibration is analyzed.The experimental data show that the prototype is in line with the design requirements.