Error analyses of filling control systems for liquid amount-given
It is of instructive significance to systematically analyze the factors that influence the precision of filling control systems for liquid amount-given. The sources of additional errors of volumetric flowmeter and Coriolis mass flowmeter were analyzed in the paper. The factors that influence the filling overshoot and lead to overshoot error were discussed in particular. Then the general system error was expressed and the main approaches to improving the filling precision were summarized. It is indicated that the filling precision of system is mainly decided by the precision of flowmeter and other instruments such as thermometer and manometer on condition that the valve is shut off in advance under low instantaneous flowrate. The influence of overshoot error on the filling precision of system is not remarkable.
The identification of external factors which influence the calibration of Coriolis massflow meters
Abstract It has been suggested that, by monitoring the sensor signals and the meter drive signal, it may be possible to create a Coriolis meter which can identify the presence of a variety of external disturbances and can give a warning and/or make a correction to the meter output in order to maintain accuracy. This paper presents the findings from an investigation of the response of commercially available Coriolis meters to such disturbances. The results of this program of tests are reported and the implications of these results on the practicality of the creation of an ‘intelligent’ meter are discussed.
THE SIMULATION OF CORIOLIS METER RESPONSE TO PULSATING FLOW USING A GENERAL PURPOSE F.E. CODE
The publication of a theoretical analysis of the response of a simple straight-tube Coriolis meter to flow pulsations raised the question of the extent to which the results of that analysis are generic over the wide range of geometric configurations used in commercially available meters. A procedure for using a general purpose finite element (FE) code to investigate this question is presented. The dual time scales, which are an essential feature of pulsating flow through a Coriolis meter, are used to minimize the amount of computation required to simulate the meter response. The FE model is developed in a full 3-D form with shear deflection and axial forces, and the computation of the simulated response for the geometrically most complex meter currently available shows that this level of representation is necessary to reveal the full details of the response. The response derived from the FE simulation for straight-tube meters, is compared with the published theoretical response and to experimental data. Over a range of different meters, the characteristics of the sensor signals in the presence of flow pulsations are shown to be generally similar. In all cases, the simulated sensor signals contain components corresponding to beating between the pulsation frequency and the meter drive frequency, in addition to the main component at the drive frequency. Spectra are computed from the simulated meter responses and these are used to show that the relationship between the mass flow rate and the phase difference between the component of the sensor signals at the drive frequency, is not significantly affected by the pulsations. Thus, the work suggests that the reports of changes in meter calibration due to certain frequencies of flow pulsation represent errors in signal processing rather than fundamental changes in the meter characteristics.