Method of forming adaptive weighting coefficients of a tof flowmeter based on resonance channel data of sound velocity

Abstract

This paper proposes a method for adaptive formation of weighting coefficients in a multichannel ultrasonic time-of-flight (TOF) flowmeter using independent information on the speed of sound in the working medium obtained a resonant RES channel. Unlike the conventional approach, in which the contribution of individual acoustic paths is determined by constant spatial weights, the proposed method additionally modifies the basic weighting coefficients according to the current metrological consistency of each TOF channel. For each TOF channel, the mean flow-velocity component along the acoustic path (vi) and the effective speed of sound (ci) are determined the measured ultrasonic signal transit times in the downstream and upstream directions. An in- dependent estimate of the speed of sound (cRES) is provided by a resonant channel oriented perpendicular to the main flow direction. An algorithm has been developed that implements sequential determination of the TOF- and RES-channel parameters, evaluation of their metrological consistency within a moving time window, formation of reliability coefficients, normalization of adaptive weights, and monitoring of an integral reliability indicator of the measurement structure. Based on the discrepancy between ci and cRES, a dimensionless reliability coefficient is formed and used to modify the basic spatial weight. The resulting adaptive weight is defined as the normalized product of these quantities. To reduce the influence of individual outliers, robust estimation of the inconsistency within a moving time window is proposed. In addition, an integral indicator (Sq) is introduced to characterize the preservation of reliable spatial information.