Sensor interfaces: from field-bus to Ethernet and Internet

Traditionally, the 4-20 mA analog signal used in industry to interface sensors in distributed process control has been replaced with relatively simple digital networks, called "field-buses", and recently by Ethernet. In this work, three interfaces for a simple sensor, based on the same architecture and microcontroller, have been implemented and tested: Profibus-DP, CANbus2.0B and Ethernet IEEE802.3. The experimental results show that the Ethernet interface, although less efficient than field-bus interfaces, requires about the same resources, in terms of computing power and memory space for code and data storage. As an Internet-capable sensor could be virtually reached from everywhere. for remote control and diagnosis, the feasibility of an Internet interface has been investigated. A full-compliant implementation of high-level protocols as TCP/IP or HTTP needs many resources to be implemented, resulting too expensive for a "smart sensor". For this reason, a simple UDP-based solution, that preserves Internet visibility, has been proposed and implemented. Obtained results match with a low-cost smart Internet-sensor. (C) 2002 Elsevier Science B.V. All rights reserved.