Showing papers in "IEEE Sensors Journal in 2001"

Inertial sensor technology trends

Abstract: This paper presents an overview of how inertial sensor technology is applied in current applications and how it is expected to be applied in nearand far-term applications. The ongoing trends in inertial sensor technology development are discussed, namely interferometric fiber-optic gyros, micro-mechanical gyros and accelerometers, and micro-optical sensors. Micromechanical sensors and improved fiber-optic gyros are expected to replace many of the current systems using ring laser gyroscopes or mechanical sensors. The successful introduction of the new technologies is primarily driven by cost and cost projections for systems using these new technologies are presented. Externally aiding the inertial navigation system (INS) with the global positioning system (GPS) has opened up the ability to navigate a wide variety of new large-volume applications, such as guided artillery shells. These new applications are driving the need for extremely low-cost, batch-producible sensors.

Overview of automotive sensors

Abstract: An up-to-date review paper on automotive sensors is presented. Attention is focused on sensors used in production automotive systems. The primary sensor technologies in use today are reviewed and are classified according to their three major areas of automotive systems application-powertrain, chassis, and body. This subject is extensive. As described in this paper, for use in automotive systems, there are six types of rotational motion sensors, four types of pressure sensors, five types of position sensors, and three types of temperature sensors. Additionally, two types of mass air flow sensors, five types of exhaust gas oxygen sensors, one type of engine knock sensor, four types of linear acceleration sensors, four types of angular-rate sensors, four types of occupant comfort/convenience sensors, two types of near-distance obstacle detection sensors, four types of far-distance obstacle detection sensors, and and ten types of emerging, state-of the-art, sensor technologies are identified.

An ultrasonic sensor for distance measurement in automotive applications

Abstract: This paper describes an ultrasonic sensor that is able to measure the distance from the ground of selected points of a motor vehicle. The sensor is based on the measurement of the time of flight of an ultrasonic pulse, which is reflected by the ground. A constrained optimization technique is employed to obtain reflected pulses that are easily detectable by means of a threshold comparator. Such a technique, which takes the frequency response of the ultrasonic transducers into account, allows a sub-wavelength detection to be obtained. Experimental tests, performed with a 40 kHz piezoelectric-transducer based sensor, showed a standard uncertainty of 1 mm at rest or at low speeds; the sensor still works at speeds of up to 30 m/s, although at higher uncertainty. The sensor is composed of only low cost components, thus being apt for first car equipment in many cases, and is able to self-adapt to different conditions in order to give the best results.

Silicon piezoresistive stress sensors and their application in electronic packaging

Abstract: Structural reliability of integrated circuit (IC) chips in electronic packages continues to be a major concern due to ever-increasing die size, circuit densities, power dissipation, operating temperatures, and the use of a wide range of low-cost packaging materials. A powerful method for experimental eval- uation of silicon die stress distributions is the use of test chips incorporating integral piezoresistive sensors. In this paper, a review is made of the state-of-the-art in the area of silicon piezore- sistive stress sensor test chips. Developments in sensor theory, calibration methods, and packaging applications are presented. In the absence of die failure, packaging-induced stresses result in changes in the parametric performance of circuitry on the die, and the theory discussed here can be used to predict such changes. Index Terms—Electronic packaging, piezoresistive, stress sensor, test chip.

Environmental gas sensors

Abstract: Due to the dramatic growth in industrial development and population, the natural atmospheric environment has become polluted and is rapidly deteriorating. Thus, the monitoring and control of such pollutants is imperative to prevent environmental disasters. Conventional analytic instruments for this purpose are time consuming, expensive, and seldom used in real-time in the field. As such, a solid-state gas sensor that is compact, robust, with versatile applications and a low cost, could be an equally effective alternative. Accordingly, this paper presents a brief overview of solid-state gas sensors, which can be classified into semiconductor, capacitor, and solid-electrolyte type sensors, based on their sensing mechanisms and a simple NDIR instrument. Furthermore, the sensing properties of solid-state gas sensors to environmental gases, such as NO X , SO X , CO 2 , volatile organic compounds (VOCs), plus certain other gases, are also classified and summarized.

Chemical sensors for portable, handheld field instruments

Abstract: A review of three commonly used classes of chemical sensor technologies as applicable to implementation in portable, handheld field instruments is presented. Solid-state gas and chemical sensors have long been heralded as the solution to a wide variety of portable chemical sensing system applications. However, advances in optical sensing technology have reduced the size of supporting infrastructure to be competitive with their solid-state counterparts. Optical, solid-state, and hybrid arrays of sensors have application for portable instruments, but issues of insufficient selectivity and sensitivity continue to hamper the widespread introduction of these miniaturized sensors for solving chemical sensing problems in environments outside the laboratory. In this article, we evaluate three of the major classes of compact chemical sensors for portable applications: (solid-state) chemiresistors, (solid-state) CHEMFETs, and (optical) surface plasmon resonance sensors (SPR). These sensors are evaluated and reviewed, according to the current state of research, in terms of their ability to operate at low-power, small-size, and relatively low-cost in environments, with numerous interferents and variable ambient conditions.

A contribution on some basic definitions of sensors properties

Abstract: HE continuous progress of the microelectronic technologies together with developments in material science has sustained the sensor area growth for many years. Contributing to sensor progress are advances in chemistry, biology, surface science, chaos and information theory, signal processing, nanotechnology, and simulation tools. All of these aspects, which are strongly pluridisciplinary in character, together with promising markets on the horizon in the fields of medicine, industrial processes, transportation, space, and food and beverage control, are contributing to the birth of the sensor science discipline. Moreover, the rather recent interests and efforts in many laboratories all over the world, in the DNA chip studies and genoma projects and in transgenic technologies, have enlarged even more the positive perspective of this rather young scientific domain. A positive consequence is its relevance and importance particularly in the development of social life in the near future. Some of the new branches of this revolution, for instance, bioinstrumentation, will certainly require more and more nanobiosensors which, although not yet completely identified, will certainly be promoters of new themes of advanced research and of needs of new fine technologies and nanometrology. In order to allow a coherent sensor development from both the scientific and technical point of view, it is necessary to promote an accurate dissemination of scientific information among all those interested in the sensor area. The knowledge of standards and that set of definitions, which have their roots into the branch of the measurement sci

Temperature sensors and voltage references implemented in CMOS technology

Abstract: This paper reviews the concepts, opportunities and limitations of temperature sensors and voltage references realized in CMOS technology. It is shown that bipolar substrate transis- tors are very suited to be applied to generate the basic and PTAT voltages. Furthermore, it is shown that dynamic element matching and auto-calibration can solve the problems related to mismatching of components and noise. The effects of mechan- ical stress are a major source of inaccuracy. In CMOS technology, the mechanical-stress effects are small, as compared to those in bipolar technology. It is concluded that, with low-cost CMOS tech- nolog, rather accurate voltage references and temperature sensors can be realized.

Micromachined water vapor sensors: a review of sensing technologies

Abstract: The measurement of water vapor is important in many applications ranging from predicting changes in the weather to ensuring heating and cooling comfort in homes. In manufacturing, water vapor measurements help to control performance properties of engineered materials and optimize fuel efficiency in power generation. This paper presents a technology review of water vapor sensors and manufacturing techniques. Micromachining, more commonly known as MEMS or microelectromechanical systems, is an enabling technology based upon standard semiconductor manufacturing. MEMS technology makes possible solid-state sensors with greatly reduced power consumption and low operating voltage that are fully compatible with digital electronics and can be manufactured in high volumes at low cost. A water vapor microsensor just becomes another part on the circuit board. A "technology roadmap" for water vapor microsensors is defined where the sensing technologies have been organized into four major transduction schemes: capacitive, mass-sensitive, optical and resistive. Sensing element type, key geometric features and excitation scheme provides further classification. Operating principles and general performance characteristics are also presented.

SAW-based radio sensor systems

Abstract: Surface acoustic wave (SAW) devices can be used as identification and sensor elements (SAW transponders) for mea- suring physical quantities such as temperature, pressure, torque, acceleration, humidity, etc., that do not need any power supply and may be accessed wirelessly. The complete wireless sensor system consists of such a SAW transponder and a local radar transceiver. An RF burst transmitted by the radar transceiver is received by the antenna of the SAW transponder. The passive transponder responds with an RF signal—like a radar echo—which can be received by the front-end of the local transceiver. Amplitude, frequency, phase and time of arrival of this RF response signal carry information about the SAW reflection and propagation mechanisms which in many cases can be directly attributed to the sensor effect for a certain measurand. Usually no intersymbol interference (ISI) due to environmental echoes occur, due to the high delay time of the SAW transponder in the order of some s. The present work reviews the operating principles of such sensor systems and their state-of-the-art performance by way of some examples which include the wireless measurement of temperature, pressure, torque, acceleration, tire-road friction, magnetic field, and water content of soil. Index Terms—Acceleration, local radar transceiver, magnetic field, passive SAW transponder for sensing, pressure, temper- ature, tire-road friction, torque, water content of soil, wireless measurement.

Multicomponent gas mixture analysis using a single tin oxide sensor and dynamic pattern recognition

Abstract: A new method, which is based on the discrete wavelet transform, is presented for extracting important features from the response transients of a micromachined, tin oxide-based gas sensor. It is shown that two components in a mixture can be simultaneously and accurately quantified by processing the response dynamics of a single sensor operated in a temperature-modulated mode. The discrete wavelet transform outperforms the fast Fourier transform (classical approach) because it is more appropriate for the non- linear frequency-time problem encountered here.

Review of thickness-shear mode quartz resonator sensors for temperature and pressure

Abstract: This work reviews the use of thickness shear mode resonators for temperature sensing and pressure measurement. Advantages of such sensors include inherently digital format, high resolution, high accuracy, and long-term stability. This work reviews the physical principles involved in the operation of the devices along with quoted sensor performance results. The earliest commercially available temperature sensors were stand-alone units. Their use and commercial success evolved through different stages depending in part on ancillary electronics available at the time. A number of temperature-sensing applications are ancillary to other thickness shear resonator sensors. Two main categories are separate resonator for temperature compensation and dual-mode operation of a single thickness shear resonator. Dual-mode oper- ation subdivides into use of two modes from different thickness shear mode families or two modes from the same thickness shear mode family. A variety of pressure sensors use the fact that the frequency of a thickness shear resonator changes with stress bias. Such applica- tions divide conveniently into categories dependent on the pattern of stress bias used.

Target acquisition performance modeling of infrared imaging systems: past, present, and future

Abstract: This paper provides a 40-year review of the infrared imaging system modeling activities at the U.S. Army Night Vision and Electronic Sensors Directorate (NVESD). The result of these modeling activities is a system model that describes the target ac- quisition performance of a human observer and an infrared im- ager. The model has been adopted by the military infrared imaging community as an assessment of how well an ensemble of observers perform the tasks of target detection, recognition, and identifica- tion. The model is used in infrared imager design and assessment, where military users understand how the metrics predicted by the model relates to system performance on the battlefield. This review begins with early work in the late 1950s and proceeds to present day modeling successes. Finally, the infrared imaging system mod- eling activities for the future are discussed. Index Terms—Infrared imaging, modeling.

SAW sensors for harsh environments

Abstract: Surface acoustic wave (SAW) sensors are rugged components made on highly stable substrate materials. In addi- tion, by their operating principle they lend themselves to wireless readout by radio signals. For these reasons, they are a first choice for sensing in harsh environments. A review is given on SAW device design, instrumentation of sensor systems, and on the physical interactions underlying sensing mechanisms. Recent progress in chemical as well as physical sensing toward various applications, e.g., in pollution control, biomedicine, and industry, is highlighted. Index Terms—Chemosensors, coatings, detection limit, high temperature, instrumentation, resolution, selectivity, sensing mechanisms, sensitivity, sensor materials, surface acoustic waves, torque.

Ferroelectric sensors

Abstract: The growing class of ferroelectric sensors covers a broad spectrum of devices based on piezoelectric, electrostrictive, pyroelectric, dielectric, and conduction phenomena. It finds applications in as diverse and wide areas as industrial production, automotive and aerospace applications, communications, health care, and environmental monitoring. In this brief review, we first introduce the physical phenomena underlying the major types of ferroelectric sensors and the materials used. Then, the principal types sensors are described: infrared sensors, pressure sensors, force and motion sensors, flow sensors, hydrophones, ultrasonic transducers for medical imaging and material testing, and a variety of devices based on the exponential temperature dependence of resistivity. Emphasis is placed on recent advances and emerging technologies, such as thin-film array devices and novel single crystal sensors.

Temperature-insensitive dual-mode resonant sensors - a review

Abstract: Dual mode excitation of resonators allows the highly accurate measurement of, and compensation for, the effects of temperature, pressure, etc., by means of frequency measurements alone. Frequency can be measured with far higher accuracy than any other quantity. In dual mode excitation, the two excited modes occupy the same volume of quartz, thereby allowing the resonator to sense two measurands simultaneously, e.g., pressure and temperature. This paper reviews the dual-mode technique and its sensor applications.

The piezojunction effect in silicon sensors and circuits and its relation to piezoresistance

Abstract: Mechanical stress has a significant effect on the elec- trical characteristics of silicon transistors through the piezojunc- tion effect. This effect is physically related to the piezoresistive ef- fect, but its results are quite different. Both effects can be applied to sensor devices. They can also have a negative effect on circuit performance and this may need to be minimized. This paper gives a overview of the physical causes and shows how understanding of the piezojunction effect can be used to maximize it for sensors and minimize it for circuits.

An overview and a contribution to the optical measurement of linear displacement

Abstract: The present work is a contribution to the field of linear displacement measurements by optical means. For that purpose, a brief overview of some existing solutions is presented and two systems for axial linear displacement measurement based on light intensity detection are introduced. The systems have redundancy and were designed with the purpose of achieving identification and automatic correction of errors arising from inadvertent angular variations between the sensor and the light beam positions.

A review of cryogenic thermometry and common temperature sensors

Abstract: This paper reviews cryogenic temperature sensors and gives an overview of cryogenic thermometry over the range 20 mK to 100 K. It begins with a brief overview of primary thermometry and methods used to realize and disseminate the International Temperature Scale of 1990, ITS-90. A short review of secondary thermometry is presented, focusing the discussion on commonly available sensors. The integration of temperature sensor to a total measurement system is discussed as well as potential sources of measurement error.

Nanometer-scale force sensing with MEMS devices

Abstract: In recent years, many researchers have adapted lithography, deposition, and etching techniques from the IC processing community for the fabrication of micromechanical sensors. Many of the signals that these sensors are intended to detect are expressed as forces which stress or deflect the micromechanical structure. As sensors are miniaturized, these forces naturally become smaller, and techniques for detection are required to improve. Many researchers have been engaged in extending MEMS force sensing to the nanometer scale by incorporating new materials and fabrication approaches. This paper will discuss the issues and limitations related to sensing on the nanometer scale and review recent work in this field.

Laser-scanned p-i-n photodiode (LSP) for image detection

Abstract: Amorphous and microcrystalline glass/ZnO:Al/p(a-Si:H)/i(a-Si:H)/n(a-Si 1 - x C x :H)/Al imagers with different n-layer resistivities were produced by plasma-enhanced chemical vapor deposition technique (PE-CVD). The transducer is a simple, large area p-i-n photodiode; an image projected onto the sensing element leads to spatially confined depletion regions that can be readout by scanning the photodiode with a low-power modulated laser beam. The essence of the scheme is the analog readout and the absence of semiconductor arrays or electrode potential manipulations to transfer the information coming from the transducer. The effect of the image intensity on the sensor output characteristics (sensitivity, linearity, blooming, resolution, and signal-to-noise ratio) are analyzed for different material composition. The results show that the responsivity and the spatial resolution are limited by the conductivity of the doped layers. An enhancement of one order of magnitude in the image intensity and on the spatial resolution is achieved with a responsivity of 0.2 mW/cm 2 by decreasing the n-layer conductivity by the same amount. In a 4 x 4 cm 2 laser-scanned photodiode (LSP) sensor, the resolution was less than 100 μm and the signal-to-noise (S/N) ratio was about 32 dB. A physical model supported by electrical simulation gives insight into the methodology used for image representation.

Plant acoustic density profile model of CTFM ultrasonic sensing

Abstract: Many applications require the sensing of plants. When an ultrasonic sensor insonifies a plant, the resultant echo is the superposition of the echoes from the leaves. As a result, the echo contains information about the geometric structure of the foliage. In this paper, we present a model of sensing that facilitates the extraction of geometric features from the echo for plant classification, recognition and discrimination. We model the echo from a CTFM ultrasonic sensor with the acoustic density profile model. Then, we identify a set of features that represent plant geometric characteristics and use these to perform an inverse transform from echo features to plant geometry.

Analytical solutions of sensitivity for pressure microsensors

Abstract: Pressure microsensors are normally designed in linear operation range. In this study, analytical solutions are presented in order to offer a set of simple equations to designers and researchers to calculate and predict the sensitivity of pressure microsensors. The pressure sensitivity is proportional to the square of the ratio of diaphragm thickness to diaphragm length, but it is inversely proportional to burst pressure. We found that the analytical solutions are in good agreement with simulation by finite element method.

Galvanic cell formation: a review of approaches to silicon etching for sensor fabrication

Abstract: A brief review of silicon etching and electrochemistry provides an introduction to galvanic cell formation in silicon/metal contacts in aqueous electrolyte solutions. It is shown that such gal- vanic cells, which operate under open-circuit conditions, can be used to perform most of the functions of anodic etching and pas- sivation. Applications relevant to sensor fabrication are described. These include the control of surface morphology, etch-stop mech- anisms, and microporous and macroporous etching. In addition, surface structuring by open-circuit photoetching, a process which also depends on galvanic effects, is considered.

Dynamic thermal sensor - principles in MEMS for fluid characterization

Abstract: Using thin-film technology with its characteristic low masses and high aspect ratios a new range of possibilities is made available for the use of dynamic thermal measuring principles. Based on this, a micromachined sensor was developed for the measurement of transient thermal signal responses leading to the thermal characterization of fluids at low sample volumes. The achieved resolution allowed the measurement of thermal parameters of the investigated fluids, i.e., thermal conductivity and specific heat, inside microfluidic systems at a high sensitivity, enabling the detection of inter-fluid boundaries, e.g., as found in micromixers and -reactors, making the sensor a useful tool for micro fluidic system characterization. This is achieved via the measurement of the frequency dependent thermal signal response.

Catalytic sensors for monitoring explosive atmospheres

Abstract: Catalytic sensors have a long history of use in environmental health and safety applications for detection of potentially explosive atmospheres. The active element of the modern sensor is a sophisticated microcalorimeter that measures the heat of combustion liberated as the combustible analyte is oxidized on its catalytic surface. A well-designed sensor is sensitive for a wide range of hydrocarbon gases, provides a linear response with increasing concentration, and consumes little power. Environmental catalyst poisons, such as volatile silicones and sulfur compounds, pose the greatest threat to long sensor life. Fortunately, several approaches to eliminate or reduce the effects of poisons are available. Future catalytic sensors are likely to be smaller and more energy efficient than today's models, reflecting trends in portable instrument design.

Development of novel optoelectromechanical systems based on "transparent metals" PBG structures

Abstract: Developed a novel smart optoelectromechanical structure, fabricated using a multilayer, metal-dielectric photonic band gap (PBG) structure We discuss innovative devices with electrically controllable optical properties that can be used as sensors with optical output signals for applications in harsh or hostile environments (pressure sensors, micro gravimeter, or micro accelerometer) or as optical modulators and optical limiters Theoretical models of these novel devices together with experimental prototypes have been developed, and characterization of the devices has been performed Moreover, microelectromechanical devices have been studied for application to this field and are presented In particular, the problem of realizing highly sensitive accelerometers has been addressed, and it will be shown that the proposed approach allows detecting displacements of a few nanometers

RF sensing of grain and seed moisture content

Abstract: A brief review is presented on the electrical properties of cereal grains and their use in sensing moisture content of grain and seed. The basic principles are described for using radio-frequency (RF) (including high frequencies and microwaves) dielectric properties, or permittivity, of grain for sensing moisture through their correlation with moisture content. The development of density-independent functions of the permittivity is explained. The findings of recent research are summarized, which indicate that reliable density-independent moisture content determinations can be realized by on-line RF measurements. Development of these techniques will provide useful instruments for on-line monitoring of moisture content in flowing grain and other particulate materials to manage moisture content, prevent spoilage in storage and transport, improve processing, and provide information important for yield determinations in precision agriculture applications.

New CMOS-compatible mechanical shear stress sensor

Abstract: A new approach to the measurement of mechanical stresses is presented. The new sensor design utilizes the fact that shear stresses in the silicon lattice generate an electric field perpendicular to an electric current. The sensor effect is characterized by a new piezo-bridge-coefficient, which relates the sensitivity of the sensor structure to its crystallographic orientation. The sensor is based on a CMOS-compatible structure. It offers the possibility to realize highly sensitive single-element stress sensors for use in MEMS or in smart force measurement strips, as well. An example of a signal conditioning circuit is shown. Special designs with improved sensitivity and low noise are presented. The response to parasitic magnetic fields is measured and strongly reduced. Furthermore, the temperature behavior was analyzed and finally optimized.

Electromagnetic flowmeters for open channels - two-dimensional approach to design procedures

Abstract: In this paper, we present a two-dimensional (2-D) ap- proach to electromagnetic flowmeters design. Several design pro- cedures that have been prepared and tested for designing electro- magnetic flowmeters for open channels are presented. The authors present a simplified 2-D mathematical model of a flowmeter for de- termining the cross-sectional shape and length of an excitation coil. We analyze two groups of flow channels: rectangular nonconduc- tive flow channels, and conductive flow channel with any shape of a cross section. Finally a dry calibration procedure determines the transfer function of a flowmeter.