Study On Differential Pressure Feedback And Control Technology Of Precise Gear Flowmeter

Flowmeter is a common tool to measure flow,and was widely used in various fields such as industrial production.Gear flow meter has a larger share in the flowmeter market due to its simple structure.The gears of traditional gear flowmeters are driven by the fluid,so the inside leakage happens when the speed of the fluid changes sharply,which causes the precision of measurement to decline.Therefore the realization of measurement with high precision of gear flowmeter is an urgent engineering problem to be solved.In recent years,the gear flowmeter with high precision combining mechanical and electronic control system has emerged abroad,which can measure with no differential pressure.The flowmeter has been widely used in the gas turbine industry of automobile,but the price is very high because they are all imported.For this problem,this paper aims to develop a gear flowmeter measuring system with feedback and control of differential pressure to improve the accuracy of measurement.By analyzing the present gear flowmeters,a flow measurement system of gear flowmeter with feedback and control of differential pressure was developed.The software and hardware of the flow measurement system were completed.Firstly,the differential pressure detection module is designed through comparing the advantages and disadvantages of several plans.According to the principle of Linear Variable Differential Transformer(LVDT),The differential pressure detection module is designed based on AD698,the processor chip of LVDT’s signal.Then the direct current motor driving circuit based on A4950 and power conversion circuit,filter clamp circuit,encoder interface circuit,communication interface hardware circuit were designed.In software,the software of the flow measurement system was completed,including the main software,motor motion control algorithm based on PID,ADC conversion,timer to transmit PWM and receive encoder’s pulse,timer interrupt service function,OLED screen display,serial communication,etc.The prototype and experimental platform were set up.The calibration and testing experiments were carried out and the testing datum were summarized and analyzed.The experimental results show that the differential pressure between the entrance and exit measurement and adjustment are effective,the system long working stability is excellent,and the relative error is less than 0.5%,its range ability is 0-80 L/h.The flow measurement system can be used in the fields of high precision.