Study On Ultrasonic Flowmeter Of Short Tube

Principles of ultrasonic propagation in fluids containing information of fluid is used by ultrasonic flow meter,receiving signal computing into flow.With the deepening of ultrasonic technology, ultrasonic flowmeters are used more and more widely, have become an important industrial test instrumentation system.Ultrasonic flowmeters of clamp-on,plug-in, pipe-stage are uded commonly.Ultrasonic flowmeter of short tube is the probe and the measurement tubes specially constitute together, placed in the pipeline to flow measurement,mainly used for flow measurement of oil field injection well.At present,ultrasonic flowmeter based on propagation time difference method used widely.Accuracy of propagation time measurement is the key to affect this type of flow measurement, therefore, the propagation time must use high-precision measurement methods to ensure the accuracy of flowmeter.The traditional ultrasonic flowmeter had low accuracy and great influence by temperature.To solve the above problem,a new ultrasonic flowmeter is designed which use double MCU as the core.The probe and special measurement tubes made together,and the probe contacts directly with the fluid to reduce the attenuation.Consider of measurement accuracy restricted by internal maste frequency or reference frequency,from design of hardware circuit,the perspective of external hardware using a MCU extended counting circuit,by increasing the reference counter to increase the frequency of the system's timing accuracy.High-speed CMOS counter 74AC161 and 133MHz high-precision frequency oscillators are used by the ultrasonic flowmeter,to improve the accuracy of measurement and reduce the cost Improved algorithm with the time difference is used,which removed the ultrasonic wave velocity affecting the measurement accuracy,to ensure the accuracy of measurements and ensure a high accuracy,to avoid temperature changes on ultrasonic measurement.Time difference of ultrasonic wave propagation in a fluid is in ns. It is more difficult to accurately measure time difference.Multi-pulse time difference measurements method is used,to avoid the measurement of small time difference of magnitude, measure summationof N time difference.Dedigne of threshold circuit, zero circuit are used by the ultrasonic flowmeter,by minimizing measurement error,improving the accuracy of measurement and enhancing anti-jamming capabilit.Use of existing conditions, multi-pulse time difference measurements is tested,average value used in the digital filtering method for analysis of data.It is proved by experiment that the system has high accuracy,loe cost,which is feasible.