The Calibration Of Time Parameter Of Ultrasonic Flowmeters With Large Diameter

Ultrasonic Flowmeters with Large Diameter has been widely used in flow measurementof water conservancy, electric power, petroleum, chemistry and other industrial fields. It hasmany advantages, such as wide measuring range, convenient installation, high measurementaccuracy. However, It will cause the economic losses badly with its low current measurementaccuracy in long time. It is necessary to evaluate accurately measurement uncertainty ofinfluence factors to provide the measurement accuracy.In this paper, through the massive related literature materials calculation and the fulltheory, the effect of time parameters of large aperture and transit time ultrasonic flowmeterhas been studied with starting from non practicable flow calibration. And three sets ofexperiment schemes had been designed for the time parameter of ultrasonic flowmeters withlarge diameter. The main work and innovation were as the following:1. The measurement theory was deeply researched with time-difference-type ultrasonicflowmeters which was including ultrasonic transmission in liquid and influence factors. Themain research focuses on the ultrasonic travel time and time difference. In the research ofultrasonic travel time, the system time delay was recorded as a part of the ultrasonic traveltime. And the relative error of the system delay of ultrasonic transmission was approximatelyequal to the opposite relative error of velocity measurement. In the research of time error, thefluid flowing was proportional to the time difference and It would be eliminated theuncertainty of the system delay from the calculation of theory and the uncertainty of themeasurement of the speed of sound was brought.2. Three sets of experiment solutions was designed for ultrasonic travel time and timedifference of ultrasonic flowmeters with large diameter. It contained that the system delaycalibration device for ultrasonic travel time, digital delay and coaxial cable delay device fortime difference. I have completed the experiment and data analysis tasks with two solutionsof the system delay calibration device and digital delay device. And it was completed aboutthe experiment designing and analysis of the coaxial cable delay device. 3. It was larger workload and longer experiment cycle to calibrate respectively each ofthe ultrasonic transducers in the calibration of flowmeter timing system delay. The accuracyof ultrasonic travel time was significantly improved when getting the delay of ultrasonicflowmeter timing system and providing reasonable modification. Digital delay device wasused to calibrate synchronously the time difference of all the transducer pairs conveniently.But the equipment was badly general with the technical protection of manufacturers. Thephysical cable was as the part of coaxial cable to simulate time difference with installing inthe outside cable of the flowmeters. It was calibrated for the mainstream ultrasonicflowmeters because of reducing the opening degree of the manufacturer technology inmarket.4. It has been discussed about the advantages and disadvantages of the calibration of thethree sets of devices and provided for the experimental options of non practicable flowcalibration of the time parameter.