On-line compensation in a digital Coriolis Mass Flow meter

Abstract

For many years it has been demonstrated that the use of digital technology, particularly embedded microprocessors, can improve flowmeter performance in various ways (e.g. temperature compensation, elimination of drift, generation of engineering units, diagnostics). A self-validating or SEVA sensor uses in-built processing power to generate generic metrics of measurement quality, based on on-line uncertainty. This uncertainty includes all factors effecting the on-line measurement, including diagnostics but also manufacturing aspects such as the components used and the characterisation procedure. This paper describes a prototype SEVA coriolis mass flow meter transmitter built primarily from digital components, which provides compensation for both faults and manufacturing limitations. A technique to compensate for drift and imbalance in the transmitter front-end circuitry is described in detail. The prototype has been developed using a hardware/software co-design approach in which virtually all aspects of instrument design are described in software, but which can be implemented flexibly in either hardware or software according to economic requirements. This approach offers manufacturers the opportunity of incorporating the latest components into their products rapidly in order to remain competitive.