The design of distributed measurement systems based on IEEE1451 standards and distributed time services

Abstract

This paper discusses the design challenges in creating effective and robust distributed measurement and control systems. The design of distributed measurement systems is greatly facilitated by recent standards such as IEEE1451.1 and IEEE1451.2, and the existence of network infrastructure features such as distributed time services. The point-to-point connection between the central controller and a peripheral is usually accomplished via a serial protocol such as RS-232, HART/sup TM/, or a specialized bus such as IEEE488. A distributed design allows additional degrees of freedom to meet real-time requirements and an opportunity to build more flexible yet more robust systems. A variety of infrastructure services, such as TDMA protocols typified by the Sercos protocol and the MARS/sup TM/ system, exist to aid in this coordination. Another approach is to use services built on a global sense of time established by synchronizing real-time clocks contained in each component. These services are discussed both theoretically and in terms of an example system. To illustrate these points, a simple distributed measurement system is examined both in terms of the design issues and the performance. This system has been constructed out of a mixture of commercially available and prototype components that make use of Ethernet, the IEEE1451 standards, synchronized clocks, and commonly available commercial infrastructure services and components such as Web browsers, databases and other common application tools.