The Design And Investigation Of Automatic-Calibration System Of Mass Flowmeter

During the automotive manufacturing process in the industrial enterprise, it is required the measurements for the flux and amount of the matter, the flow rate of fluid is the parameter which is frequently to be measured and controlled. With the expeditious development of production and technology, more and more requirements are needed to implement the testing and metrology for the flow of fluid, as well as a higher requirement is needed to evaluate the accuracy of the flow measurement.The intellectualized mass flowmeter, which processes the high accuracy and high reliability, is widely used within the field of industrial energy sources measurement, adjustment and control of process and trade custody etc. To assure the veracity of the instrument, it is required that the mass flowmeter should be calibrated on the flow calibrating rig at the period when flowmeter left factory, being used and after the maintained, its characteristic and veracity should be verified as per the procedure of National Metrological Verification Regulation. The verification for mass flowmeter is usually performed on the calibration rig, so the calibration rig should fulfill with the requirement of instrument testing characteristic, and new requirements of the accuracy, reliability of calibration rig is putting forward. Therefore, it's greatly necessary to improve the accuracy, reliability and automation of the flow calibrating rig.This article, on the basis of referring to the relevant literatures, makes a detailed analysis for the calibration principium, process control, flow stability and data processing of flow calibrating rig; considering the effect of pressure, time and temperature for the calibration; investigated and designed the control scheme of steady flow; the method of frequency conversion has been used to replace the water tower to adjust fluid flow, and achieve the steady flow automatically. At the same time, the article makes an analysis of the technique quality of flow adjustive system and the source of error. The automatic-calibration system adopts the way of computer controlled, performing the measurement, testing, control and HART,RS485 communication of multi parameters, consequently, it achieves the function of automatic calibration, data acquired, create calibrate certificates and former records query.The article makes the investigation and holistic scheme design, after the discussion and analysis for the detection, acquirement of system multi parameters (i.e. flow, pressure, temperature etc) and the disposing of real-time data ,it is determined that the auto-calibration system is build up with the computer and multi-function DAQ card. At the same time, the hardware design, selection and layout are performed. After detailed analysis of calibrating process, the main operation process and key embranchment process have been designed and optimized, the flow charts are also provided. The design of system software is developed with Microsoft Visual Basic 6.0.Experiments and application of actual production prove that the system is easy to access and operate, the stability of this automatic-calibration system of mass flowmeter is satisfactory, and the result of mass flowmeter calibration is acceptable according with the relevant regulations. The automatic-calibration system represents the advantage on the side of technology and economic, it also improves the productivity greatly and processes remarkable economic benefit and favorable application; it's with the actual significance for the manufacturer of mass flowmeter.