Table of contents

It is widely accepted that sensors form a vital and necessary part of any measurement and control system and there have been many predictions concerning the demand for such devices. The author discusses the present situation with regard to those technologies which are considered likely to play a major role in the sensors of the future. Four main sensor technologies are identified; namely those based upon resonator or variable frequency techniques, optics and optoelectronics, microelectrons or solid state techniques and integrated or 'smart' systems. Examples are presented to illustrate the advantages presented by each of these technologies and observations are made about their particular aspects and sensor configurations which are likely to see early exploitation.

Chemical sensors are being developed for a large variety of applications. Medical diagnosis, industrial process control and environmental monitoring are important application fields but chemical sensors will have an impact in other areas as well. The author discusses some application fields and overviews most of the types of chemical sensors which are used or developed at present. It also describes how the nervous system in a living body contains a number of different chemical sensors. Even though one still does not fully understand the physical mechanisms behind nerve excitation there is inspiration to be gained from studying how natural sensors operate.

Techniques and devices which are currently being used or developed to provide the vital sensing functions required in automotive applications are described. Requirements for sensors for engine and transmission (powertrain) control are listed and the accuracy and temperature range over which they have to operate are noted. Future developments for sensors are also discussed.

The introduction of powerful and compact electronic systems which can be located within a sensor housing means that the sensor must now be treated as a sub-system of potentially great behavioural complexity. The author discusses the enabling technologies which permit the hardware and software realisation of such sub-systems and proceeds to a consideration of the relationship between the sub-system and its host system. Factors which have to be taken into account are the physical connections over which signals are passed, the high-level protocols by which information is exchange and the degree to which the variability of programmed operation can be exploited.

The progress made towards solving the problem of applying robotics for small and medium batch production since 1960s has been very limited. By analysing the strengths and weaknesses of robot technology some practical rules for robotic application have been previously developed by the author. These 'laws' are further considered within the context of the needs of 'sensory' systems as an aid to robotic machinery in order to throw some light on the following: (a) the future practical architecture of robotic an sensor systems and (b) the direction for research and development to take. Most problems are concerned with the better structuring of material and component flow to and from a robotic workstation and the reduction of unstructured variability at the workplace. This is to enable sensors to be applied in a viable commercial manner.

Discusses the development of fibre optic sensors for industrial, consumer, medical and military applications. The technology will continue to be applied to inspection, imaging and switching. For continuous measurements of the key physical quantities (temperature, pressure, flow, level and displacement) multimode technology and 'point source' sensors seem most appropriate at this stage using either intensity, wavelength or rate modulation. Devices for sensing magnetic, electric, nuclear radiation and chemical quantities are also of interest. Significant development of monomode hydrophones and gyroscopes has already taken place, and now multimode technology is being applied to multiplexing multi-sensor systems, optopneumatic and optohydraulic converters and 'control-by-light' schemes. Illustrative examples of practical developments are given and key reference sources cited.

Variable frequency can be used as an information parameter in signals for measuring techniques if the measuring principle chosen favours its application, if freedom from interference is essential, transmission over long distances is necessary or easy digital conversion is desirable. The variation in frequency is in general obtained from the more or less direct influence of the quantity to be measured on an oscillator parameter. Examples with various input variables and principles of conversion are presented. With forced oscillations the phase and resonant amplitude depend on the ratio of the exciting to the natural frequency and on the damping. As examples of the utilisation of these relations, sensors for small mass increments, force and pressure, density, mass flow and viscosity are chosen.

A considerable amount of experimental work is carried out in the broad acoustics field involving the detection of fluid-borne and structure-borne waves. The principles of operation and limitations of common and more recently developed transducers for dynamic measurements are reviewed. The very critical use of transducers in intensity measurement, both acoustic and structural, is also discussed.