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Emerald Group Publishing Limited
Copyright © 1999, MCB UP Limited
The authorR.B. Yates is a Professor at the School of Engineering, Sheffield Hallam University, City Campus, Howard Street, Sheffield, S1 1WB UK. Tel: 0114 225 5555; Fax: 0114 225 3433; E-mail: firstname.lastname@example.org
Keywords Smart sensors, Sensors
A sensor generally converts a physical effect into an electrical signal. However it is rarely possible to connect a sensor directly to a computer, the signal is usually too weak, or too noisy or contains undesirable components that need to be removed. It may not be compatible with the input requirements of the computer and it may have the wrong format. Thus signal conditioning is required, and this may be undertaken at the sensor or at the computer. However, as the computer is considered a general purpose device, and the sensor a specific device, then the signal conditioning is usually seen as part of the sensor.
Thus a route to the development of a new sensor would be to first investigate the material characteristics and develop and refine the response. Then add signal conditioning, a computer system, package the sensor head and connect the components together.
However, an integrated solution implies that the signal conditioning and the sensor head should be one unit and that this unit should also (ideally) be self-powered and contain a wireless communications link to the computer system. This integrated solution may be called "smart". Such an approach holds many implications, not least is the consideration of how the complete system modifies the sensor response. The sensor cannot be considered in isolation, it is part of the system. During SPIE's Symposium on Smart Structures and Materials, last year (March, 1998), Dr Darrel Tenney, Director of Airframe Systems at the NASA Langley Research Center gave a presentation about the future of Airframe Systems, where he claimed that future research at NASA would be systems focused. He related examples of order of magnitude loss in sensor performance, when in the system as compared with on the laboratory bench. Thus the future for sensors is not only smart but also holistic, and multidisciplinary approaches are required.
An example of the multidisciplinary nature underpinning new sensors may be highlighted by describing the approach undertaken within the Electronics Research Group at Sheffield Hallam University (SHU). They are exploring new sensors for environmental pollution and detection of biologically produced toxins from bacteria such as salmonella. The phenomena of surface plasmon resonance (SPR) is exploited as a sensitive tool for the detection of small optical changes on thin dielectric coatings. A variety of different compounds may be transferred onto the metal surface using a micro-pipette to form a series of spots of different biological species with the size of several micrometers. This idea forms the basis of a SPR microscopy-based sensor array, interrogated using a CCD camera connected to a computer. Chemical and biochemical products may be detected and recognized using techniques from machine vision. Thus this sensor system encompasses biochemistry/physics/machine vision.
Such sensor systems or similar, may lead to hand held diagnostic tools. They pave the way for wearable devices. The so called "smart nose" has been the subject of research for some time, and more recently this has led to a "smart tongue". With smart sensors we can make smart people. In the long term, through bio-implants and more immediately by augmenting the items we wear with smart systems. Increasing intelligence via wearable devices is not new. Spectacles and hearing aids already correct and improve our vision and hearing. Miniature computers built into clothes may become our "smartest" use of this new technology. We will require the efforts of 3D-designers and artists to "scuplt" these accessories into usable devices by modifying the form of the user interface. Smart sensors are a key element in the evolution of information processing and ultimately these future devices may be the next step in our own evolution.