Custody transfer meter

Abstract

Apparatus and accompanying methods for a custody transfer metering system, that illustratively utilizes a dual tube Coriolis mass flow rate meter and provides accurate totalized mass flow measurements and fault detection capability, are described. Specifically, this apparatus senses time differences occurring in the movement of both flow tubes. Four such time difference measurements are taken and combined in a pre-defined manner so as to eliminate differences appearing in the electrical characteristics of analog circuitry connected to each of two sensors used to detect tube movement and thereby to advantageously increase measurement accuracy. Mass flow rate of the fluid passing through the meter is determined, as a function of the combined time measurements, in terms of normalized mass and time units and thereafter converted into user specified mass units/unit time. The resulting converted value is used to compute totalized mass flow and to set and/or update various system outputs. Thereafter, the converted value is multiplied by an appropriate time factor to provide mass flow rate in terms of user specified mass and time units. By use of normalized calculations, processing time is advantageously saved and the number of unit conversions is advantageously reduced which, in turn, increases system accuracy. A sequence of diagnostic tests is continually performed to detect a variety of fault conditions and appropriately alert the user and inhibit further totalization.