Research On The Variable-viscosity Oil Flow Calibration Device And Data Processing System

As the use of flowmeters shows, the accuracy of the measurementinstrument will be affected by viscosity, pressure, temperature and other externalfactors. In order to improve the measurement precision, these factors should bereasonably corrected. For the lack of equipment, and its own complexity, viscosity asone of the main factors that affect on instrument characteristics, is not in-depthstudied yet. To solve the problem, a variable-viscosity oil flow calibration device wasdeveloped, for research the characteristics of flowmeters that affected by viscosity.First the factors that cause the change of oil viscosity were analyzed, andseveral typical oils’ viscosity were tested by use of capillary viscosimeter. On thebasis of experiment, the method of mixing oils with different viscosity to obtain thenecessary viscosity was proposed, and approached the mathematical model of mixedoil viscosity, which related to temperature and the proportion of some oil in themixture. Secondly, the overall structure of variable-viscosity oil flow calibrationdevice was designed, which takes a standard piston volume as the transfer standard,uses compressed air as the driving force to push the piston regulator move, and getthe standard volume. Then, the test control system was developed according to thecalibration requirement of volumetric flowmeter. The system includes lowercomputer system and up system. The lower computer system which based on FPGAwas used to realize the functions of value control and signal acquisition and theupper computer system based on the platform of LabVIEW was designed to realizethe functions including human-computer interaction, verification monitoring andreport printing. At last, the standard uncertainty composition of the device wastheoretically analyzed and the standard uncertainty will be lower than0.05%. Anexperiment using high stability signal generator was made to verify the pulseinterpolation technology and test control system, the result showed that thedouble-circuit pulse interpolation technology could effectively reduce the errorcaused by the too-short check time. The result of simulation calibration showed that the calibration function of the test control system could achieve the expectedaffection.