An investigation into fieldbus and its incorporation in the design of an electronic flowmeter

Abstract

Industrial sensors and actuators are becoming increasingly complex with the inclusion of embedded microprocessors to improve performance and reduce cost. The data transmission systems traditionally used by such instruments are analogue and these can be unduly costly to implement in such digital systems while failing to take full advantage of the potential
inherent in this new breed of sensors. Fieldbus was conceived as an alternative to these traditional methods, providing a rapid, digital transmission system with the facilities to allow complex networks to be designed, run and maintained efficiently. This study provides a basic insight into Fieldbus, providing an outline of many of the available systems before
concentrating on two popular European systems, Profibus and P-Net. The results of this study are incorporated in to an industrial design project undertaken in collaboration with F. Bamford (Instruments) Ltd of Stockport. They have a design for an electronic flowmeter which, while successful in the past, is now suffering reduced sales due to the cost and inflexibility of the design. This device was redesigned to reduce cost and improve performance which, along with the incorporation of Fieldbus technology, will better allow the company to compete in the marketplace.
A comprehensive review of the design methodologies of such an instrument is presented, and these are implemented in the exhaustive design process for the flowmeter which is described in full. This not only includes steps taken to improve the performance of the unit, but also describes methods used to ensure the unit can be upgraded and adapted to operate
successfully with alternate sensors and applications to make it as flexible as possible. Various ways of implementing Fieldbus in such an instrument are also discussed, leading to the development of an interface for this unit which is capable of providing the optimal solution in both high and low volume applications. The result of this design process is a system which features improved resolution and accuracy, is better suited to the flowmeter market yet which is flexible enough to allow custom applications to be fulfilled with ease.