Performance Characteristics Of Sensors Research Articles

Elastomeric binary phase gratings for measuring acceleration, displacement, strain, and stress

This article describes the fabrication and operating principles of a device suitable for measuring displacements, stresses, strains, accelerations, and forces. The device consists of an elastomeric material with a surface relief diffraction grating embossed on its surface. Mechanical compression of this element changes the way that it diffracts light. This article also describes designs and performance characteristics of simple accelerometers and pressure sensors based on these devices.

Computer assisted diagnosis for digital mammography

This article describes the application of wavelet transform for image enhancement in medical imaging. The initial clinical application is the enhancement of microcalcification clusters (MCCs) in digitized mammograms to improve both their visualization and their detection using computer assisted diagnostic (CAD) methods. The potential universal application for improved visual interpretation of medical images using a computer monitor is also demonstrated. The early detection of MCCs is important in screening programs since their presence is often associated with a high incidence of breast cancer. The enhancement of MCCs is an excellent model for real world evaluation of the wavelet transform. The detection of MCCs presents a significant challenge to the performance characteristics of X-ray imaging sensors and image display monitors since microcalcifications vary in size, shape, signal intensity, and contrast and may be located in areas of very dense parenchymal tissue, making their detection difficult. The classification of MCCs, in turn, as benign or malignant, requires their morphology and detail to be preserved. >

Analysis of a linear position sensor with a Hall effect element

The performance characteristics of linear Hall element sensors for non-contact determination of the position of a moveable permanent magnet along a pre-established path are analysed. Simple theoretical expressions suitable for computer modelling of previously described sensors are presented. Practical measurements have verified the theoretical predictions arrived at by simulation means. Having established the validity of the basic formulae predictions of performance for a variety of magnet configurations can now be attempted using superposition principles. As an application, a method of improving the linearity of a simple sensor with a single cylinder magnet by means of shaping the cylinder to a special profile is described. An alternative example is a new high-gradient configuration of a radially symmetric sensor construction on a base of two oppositely magnetized rings.

Flexible (Kapton-based) microsensor arrays of high stability for cardiovascular applications

The design, fabrication and performance characteristics of Kapton-based planar mini and semimicro potentiometric sensors with an Ag/AgCl or a quinhydrone-based redox internal reference electrode are described. The ion-selective membranes cast from conventional and various modified PVC matrices and containing different pH-sensitive ionophores are ranked on the basis of their performances in hostile environments. The adhesive bonding strength of the different PVC membranes to the polyimide-coated Kapton substrate was quantitatively evaluated as a function of fabrication procedure and sample solution contact. The long-term stability of the electrodes was characterized by the alterations of the analytical parameters of the sensors over a period of time, as well as by determining the resistance changes of their sensing membranes.

ASTROMETRIC PERFORMANCE CHARACTERISTICS OF THE HUBBLE SPACE TELESCOPE FINE GUIDANCE SENSORS

ABSTRACT Each of the three Fine Guidance Sensors for the Hubble Space Telescope constitutes a sixth science instrument to be used for astrometry. We detail the tests and results used in choosing one of the three sensors to be the prime astrometer. The Astrometry Science team has chosen Fine Guidance Sensor (FGS) 3. FGS 3 produces position measurements on a star with V=17 with a per-axis precision of 0.003 arcsec. The interferometer response function should permit double-star astrometry at least down to V=16 for the central region of FGS 3. In a ten-hour test of the stability of POS-mode astrometric measurements made in FGS 3, we found no scale or orientation variations greater than two parts in 105. During this same time period, we found no statistically significant systematic guide star radial separation changes. Spacecraft jitter is found to be the prime determinant of astrometry success or failure.

Amitriptyline-selective plastic membrane sensors and their pharmaceutical applications

The construction and general performance characteristics of potentiometric amitriptyline-plastic membrane sensors, based on ion-pair complexes with triphenylstilbenylborate and tetra(2-chlorophenyl)borate, respectively, are described. Both electrodes show near-Nernstian responses over the range 1 x 10(-2)-7 x 10(-6) mol dm-3 with a detection limit of about 5 x 10(-6) mol dm-3. The electrodes proved useful in the determination of amitriptyline hydrochloride in pure drug substances and pharmaceutical preparations. They were also applied to the determination of content uniformity and dissolution rate of sugar-coated amitriptyline tablets. The physical processes were numerically simulated by typical equations.

Application of a Novel Force-Torque Sensor in Advanced Robot Assembly and Machining Tasks

Important fields in production processes are only to a very small extent automated by use of industrial robots, because most of today’s robots are not yet equipped with appropriate sensors. The reasons for this are above all non-satisfying performance characteristics of available sensors and unsolved questions concerning the interface between sensors and robot control systems. Using the example of a novel force-torque sensor the present paper discusses approaches to the solution of both problem areas. They are based on a well suited architecture to improve the integration of sensors and industrial robots. The most important features of the force-torque sensor are pointed out as well as the coupling of the sensor and robot control systems is described. First experimental results illustrate the presented concept.

Characteristics of p-i junction amorphous silicon stripe-type photodiode array and its application to contact image sensor

Various sandwich structures of photodiode arrays using hydrogenated amorphous silicon films fabricated under similar process conditions were compared. As a result of this comparison, the p-i junction amorphous silicon stripe-type photodiode array was studied. This photodiode array has the same excellent sensor performance characteristics for contact image sensors as the p-i-n junction type, and it has a similar process. A contact image sensor using this photodiode array with eight elements/mm resolution and A4 size is discussed. This compact, high performance sensors was applied to GIII facsimiles.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Microsensors for heat transfer and fluid flow measurements

Ongoing research on the fabrication, performance, and application of microsensors is described from the viewpoint of their use for heat transfer and fluid flow measurements. Fabrication techniques that provide micromachining capabilities for various microscale elements are discussed. The thermal and fluid microenvironment characteristic of these sensors is addressed in detail. Performance characteristics of prototype pressure sensors, humidity sensors, microviscometers, thermistors, thermocouples, and flowmeters are presented. The operation of several integrated microsensors is discussed. Potential applications are mentioned, both as low-cost substitutes for existing transducers and as specialty devices for high spatial resolution and fast response needs. Finally, the use of these ultrasmall-scale transducers for fundamental research related to miscroscale heat and mass transfer is explored.

Protection against local core accidents in liquid metal fast breeder reactors

An analysis is presented concerning the performance characteristics of sensors considered for use in protection systems of liquid metal fast breeder reactors. Alternate solutions to protection systems having one or more reactor-trip channels per fuel subassembly are proposed. Primary emphasis is placed on pressure pulse sensors, installed in the upper (and possibly also lower) coolant plenum, capable of sensing the collapse of sodium vapor bubbles. It is shown that, even for the limit-case of a complete coolant blockage of one or more fuel subassemblies, a reactor protection system based on pressure pulse sensors should be capable of effecting reactor-shutdown prior to generation of any substantial amount of molten fuel. Some preliminary experimental data regarding vapor bubble collapse are presented, showing reasonable agreement with analytical predictions. Recommendations are made regarding some potentially promising areas for further research and development with respect to protection systems for liquid metal fast breeder reactors.