Table of contents

Silicon, as a sensor material, permits the integration of a sensing element and a signal-processing circuit on a single chip. In order that this attractive concept can be realised for a given measurand, it is necessary that, (i) silicon shows a suitable physical or chemical effect, (ii) a sensor can be designed based on this effect and (iii) the sensor is compatible with the desired circuit technology. This paper presents an overview of the most important effects in silicon, the latest additions to the silicon sensor family and the first attempts to integrate sensors and circuits on one chip. Based on the experience acquired to date, the silicon sensor and the 'smart sensor' concepts are analysed and a discussion of the promises and pitfalls given.

Technological progress in microelectronics has contributed to the emergence of the concept of the 'smart' or 'intelligent' sensor. A smart sensor will be essentially composed of: transducers; conditioners; an appropriate power supply; an inner computation capability; a communication interface, for digital information; and an identification. The technologies involved for these components are discussed. These include: synergy with local industrial networks; modularity and standardisation; enhanced credibility of data (maintenance assistance, validation of measurements); increased reliability and accuracy; and a reduction in associated costs (particularly wiring).

Optical fibres have some degree of sensitivity to a wide range of external parameters. Considerable advantages can be gained by appropriate selection of core and cladding materials and by novel fibre structures and designs. By spinning the preform during fibre drawing a high degree of circular birefringence can be introduced whilst the linear birefringence becomes negligible. Such fibres can behave as sensors of magnetic fields and electric currents. By introducing a high degree of linear birefringence fibre gyroscopes capable of measuring angular rotation become possible. The introduction of rare-earth materials into the core produces absorption bands with steep edges that have a strong wavelength sensitivity to changes in temperature. This produces the basis for distributed sensors that cover a wide range of temperatures. A variety of optical fibres suitable for application to sensors and transducers are discussed.

The defects of sensor performance are reviewed in the light of the availability of modern digital methods for dealing with them. Particular emphasis is placed on modern distributed, and potentially large, instrumentation systems. Suggestions are made as to how this will change future industrial practice.

The partial pressure of oxygen in blood and the oxygen saturation of blood reflect the ability of the lungs to transport oxygen from inspired air into the bloodstream, in order to make oxygen available to the tissues. Blood gas analysis is now one of the most frequent hospital diagnostic procedures. The technique of analysing individual blood samples, however, only gives information at one point in time, a snapshot of what is happening. It is now known that large variations in these gas levels can occur over the course of a few minutes. Invasive and non-invasive techniques have become available in the last few years for continuously measuring the arterial gas levels in patients. Of these, the transcutaneous technique and, more recently, the technique of pulse oximetry are now used extensively in medicine. The author deals with the advantages and current limitations of these techniques and with some of the developments in sensor technology associated with these measurements.

Industrial metrology is concerned with sensors to measure movement of machine tool parts and monitor tool wear and the dimensions of artefacts in machining centres, sensors for robots in flexible manufacturing systems, sensors to gauge mating parts for selective assembly or allowing for interchangeability, and sensors for inspection and testing of assembled or part-assembled products. The author reviews the subject and emphasises significant advances, from the use of resonant sensor systems, edge-sensing profilers and methods of laser scanning, to acoustic emission techniques, imaging systems and the scanning tunnelling microscope.

This paper will commence with a general introduction to the concepts and technology of biosensors including some discussion of the need for sensors, the range of analytes that can be measured, the areas of application, the construction of sensors with a biological recognition/response system and the range of transducer technologies that are potentially amenable to sensor use. Examples of sensor technologies for the monitoring of substrates, proteins and immunoanalytes will be given. For example. the development will be described of a novel amperometric sensor for glucose and other substrates which incorporates oxidases in conducting organic polymers and of a miniaturised surface conductivity device for monitoring analytes such as urea. Devices capable of detecting proteinaceous analytes based on optoelectronic, sensitised semiconductor, conductimetric immunosensor and various sophisticated optical techniques will also be discussed. Future trends in biosensor research will be described.

For the first two thirds of the 20th century the development of new materials has been dominated by three major requirements - physical transportation, power generation and armament production. These three motivators have now lost their force: intellectual communication is expanding more rapidly than physical transportation: energy conservation has assumed more importance than power generation; the materials intensity of armaments has declined dramatically. Information technology in all is now the main driving force behind material development, and here the prime requirement is for materials that can convert the analogue signals of nature into the digital form required by electronic manipulators. These sensors are required in physical, chemical, metallurgical and engineering environments. Examples will be given in all four and future needs outlined.