By Topic

Sensors Journal, IEEE

Issue 5 • Date Oct. 2003

Filter Results

Displaying Results 1 - 16 of 16
  • Micro-electro-discharge machining as microsensor fabrication technology

    Page(s): 632 - 639
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (764 KB) |  | HTML iconHTML  

    This paper presents the design and fabrication of three miniaturized mechanical sensors to demonstrate the three-dimensional machining capabilities of micro-electro-discharge machining (EDM). The first sensor is an inertial bi-axial inclination sensor. The displacement of an inertial mass is measured optically by means of a two-dimensional position sensitive device (PSD). The machining freedom of micro-EDM makes it possible to produce both sensor and housing in one monolithic structure. The second sensor is an inertial uni-axial inclination sensor, which demonstrates the compatibility of the micro-EDM technology with the conventional photolithographic micromachining technologies. The mechanical structure of the sensor is machined by micro-EDM and the capacitive sensing part is produced by lithography. The aim of the integration is to set up a hybrid technology, which inherits the benefits of both micro-EDM and photolithography. The third miniaturized sensor is a three-component force sensor. The mechanical structure of the force sensor converts forces into displacements, which are measured optically. The mechanical structure of the force sensor is produced by wire-EDM and micro-EDM. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Closely coupled micro coils with integrated flux guidance: Fabrication technology and application to proximity and magnetoelastic force sensors

    Page(s): 615 - 621
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1745 KB) |  | HTML iconHTML  

    A complete process technology is introduced, allowing the integrated fabrication of micro coils in transformer configurations for micro sensors. The technology makes use of UV-depth lithography, electroplating of coil conductors and soft magnetic core structures, and SU8-dielectric for embedding and planarization. It is pointed out that SU8 is especially suitable as an embedding material due to its high aspect ratio patterning capability and excellent planarization properties. Based on these properties, a novel process flow of subsequent formation of the core galvanoform becomes possible, sparing cost and time consuming dry etching of dielectric layers. The technology's applicability is demonstrated on inductively coupled transformer sensors for distance and magnetoelastic force and torque measurements. The optimized distance sensor provides sub-micron resolution and is capable of measuring distances up to 3 mm. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Fundamental imaging properties of transillumination laser CT using optical fiber applicable to bio-medical sensing

    Page(s): 658 - 667
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (865 KB) |  | HTML iconHTML  

    We proposed and developed a novel transillumination laser CT imaging system, using optical fibers, based on the optical heterodyne detection method for biomedical use. The use of optical fibers enables portability and robustness against environmental changes such as varying temperature, air-flow shifts, and unexpected vibrations. In addition, motion-artifact-free images can be obtained with the present system as measurements can be performed with the object fixed. We experimentally investigate in detail the fundamental imaging properties of the system, that has a spatial resolution of 500 μm, a dynamic range of approximately 110 dB, and a minimum-detectable-optical power of 10-14 W as a result of the excellent properties of the heterodyne detection. Based on experimental observations, the proposed system can reconstruct tomographic images of highly scattering objects in the transillumination mode, similar to X-ray CT, at sub-millimeter spatial resolution and can derive quantitative information from the images. Finally, we experimentally demonstrate the first in-situ tomographic images of plants using the fiber-optic-based laser CT system. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Interface states in high-temperature gas sensors based on silicon carbide

    Page(s): 543 - 547
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (264 KB)  

    Silicon carbide (SiC)-based metal-insulator-semiconductor devices are attractive for gas sensing in automotive exhausts and flue gases. The response of the devices to reducing gases has been assumed to be due to a reduced metal work function at the metal-oxide interface that shifts the flat band capacitance to lower voltages. We have discovered that high temperature (700 K) exposure to hydrogen results not only in the flat-band voltage occurring at a more negative bias than in oxygen, but also in the transition from accumulation (high capacitance) to inversion (low capacitance) occurring over a relatively narrow voltage range. In oxygen, this transition is broadened, indicating the creation of a high density of interface states. We present a model of the hydrogen/oxygen response based on two independent phenomena: a chemically induced shift in the metal-semiconductor work function difference and the passivation/creation of charged states at the SiO2-SiC interface that is much slower than the work function shift. We discuss the effect of these results on sensor design and the choice of operating point. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Assessment of the final metrological characteristics of a MOEMS-based NDIR spectrometer through system modeling and data processing

    Page(s): 587 - 594
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (845 KB) |  | HTML iconHTML  

    A model of a miniaturized non-dispersive infrared (NDIR) gas analysis system, aiming to predict the final system specifications, is presented. It comprises the different elements of the NDIR detector, including a surface micromachined Fabry-Perot tunable filter. These models have been used to estimate the response of the NDIR system to different gas mixtures. Multivariate regression methods like partial least squares allow recovering the true sample composition from the IR absorption spectra measured with the NDIR system, despite the limited selectivity of the filter. Combining model and data processing permits to predict the effect on the final system specification of design parameters. Here, we compare the effect of the technology used for the filter on the system errors. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Common design techniques for BEI GyroChip quartz rate sensors for both automotive and aerospace/defense markets

    Page(s): 569 - 578
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1077 KB) |  | HTML iconHTML  

    In the early 1990s, Systron Donner Inertial Division (SDID), a subsidiary of BEI Technologies, Inc., possessed a new solid-state rate gyroscope technology that had not yet matured or captured a significant market share. Even though some success had been achieved in defense missile applications, a strategy was clearly needed to further develop the technology and lay the foundation for future growth. The strategy search led to discovery of a leading edge automotive brake system application, which, in turn, led to a radical change in design and manufacturing approaches, as well as a dramatic increase in revenues. The resultant radical cost-reduction of quartz rate sensor (QRS) components has benefit for both the automotive and the aerospace and defense (A&D) applications. Commonality of design and design techniques is leveraging high-volume, low-cost automotive components into low-volume A&D products. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A contactless capacitive angular-position sensor

    Page(s): 607 - 614
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (614 KB) |  | HTML iconHTML  

    This paper presents an absolute capacitive angular-position sensor with a contactless rotor. The sensor is mainly composed of three parts: the capacitive sensing element, a signal processor, and a microcontroller. The electrically floating rotor can be either conductive or dielectric. For the dielectric material, we chose plastic, and for the conductive rotor, we chose aluminum. The sensing element has a redundant structure, which reduces mechanical nonidealities. The signal processor has a multicapacitance input and a single output, which is a period-modulated square-wave voltage. The microcontroller acquires output data from the processor and sends them to a PC, which calculates the rotor position. Theoretical analysis, supported by experimental results, show that the sensitivity to mechanical nonidealities of the sensing element is higher in the case of a conductive rotor. The resolution of the capacitive angular-position sensor over the full range (360°) was better than 1". The measured nonlinearity was ± 100" and ± 300" for the dielectric and the conductive rotor, respectively. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Planar antiresonant reflecting optical waveguides as integrated optical refractometer

    Page(s): 652 - 657
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (472 KB) |  | HTML iconHTML  

    This paper reports on an integrated refractometer sensor, useful for measuring chemical quantities, based on antiresonant reflecting optical waveguides (ARROWs). We show that, by a suitable design, the attenuation in ARROW waveguides can strongly depend on the refractive index of the superstrate layer. We use this property to design and realize an integrated refractometer. The proposed sensor structure is unique in that it consists in the ARROW waveguide itself acting like a vertical interferometer. The device is fabricated using standard silicon technology fully compatible with bipolar and CMOS integrated circuit process. The measurement results show a sensing resolution of Δn = 6e - 4 when used in a solution with a refractive index of 1.4600. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Fabrication, characterization, and analysis of a DRIE CMOS-MEMS gyroscope

    Page(s): 622 - 631
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1461 KB) |  | HTML iconHTML  

    A gyroscope with a measured noise floor of 0.02°/s/Hz12/ at 5 Hz is fabricated by post-CMOS micromachining that uses interconnect metal layers to mask the structural etch steps. The 1 × 1 mm lateral-axis angular rate sensor employs in-plane vibration and out-of-plane Coriolis acceleration detection with on-chip CMOS circuitry. The resultant device incorporates a combination of 1.8-μm-thick thin-film structures for springs with out-of-plane compliance and 60-μm-thick bulk silicon structures defined by deep reactive-ion etching for the proof mass and springs with out-of-plane stiffness. The microstructure is flat and avoids excessive curling, which exists in prior thin-film CMOS-microelectromechanical systems gyroscopes. Complete etch removal of selective silicon regions provides electrical isolation of bulk silicon to obtain individually controllable comb fingers. Direct motion coupling is observed and analyzed. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • An automotive engine oil viscosity sensor

    Page(s): 562 - 568
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (301 KB) |  | HTML iconHTML  

    For the evaluation of the condition of automotive engine oil, the oil's viscosity is one of the most important parameters. Using microacoustic viscosity sensors, an oil-viscosity measurement can be performed on-board. In this contribution, we discuss the behavior of the viscosity of engine oil, its temperature dependence, and the resulting representation in terms of output signals of microacoustic viscosity sensors. These considerations are illustrated by means of measurement results obtained for used oil samples, which have been obtained from test cars and fresh oil samples out of different viscosity classes. Finally, the detection of the viscosity increase due to soot contamination is demonstrated. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Active structural error suppression in MEMS vibratory rate integrating gyroscopes

    Page(s): 595 - 606
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1960 KB) |  | HTML iconHTML  

    Due to restrictive tolerancing in microfabrication, structural imperfections that reduce performance of fabricated micro devices are typical. In microelectromechanical vibratory gyroscopes, feedback control is a common strategy in attempting to correct the imperfections. However, a purely feedback control can be insufficient for compensation of all the errors, requiring post processing in the form of laser trimming to achieve higher levels of performance. In this paper, we explore another alternative: the design and implementation of a dual stage control architecture with self-calibration and feedback capabilities. The self-calibrative portion of the control identifies and electronically "trims" large imperfections, while the feedback control compensates for remaining small nonidealities and in-operation perturbations. Presented here is an algorithm for in-situ imperfection identification based on the dynamic response of the device. A realization of the dual stage control architecture is proposed for a gyroscope using nonlinear electrostatic parallel plate actuators. Modeling and simulation results which demonstrate successful compensation of imperfections with the proposed architecture for a device with 10% fabrication error appearing in the form of stiffness nonidealities and subjected to further 1% in-run perturbations are presented. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A Pt/Ga2O3-ZnO/SiC Schottky diode-based hydrocarbon gas sensor

    Page(s): 548 - 553
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (416 KB) |  | HTML iconHTML  

    In this paper, a novel metal-reactive insulator-silicon carbide device with a catalytic layer for hydrocarbon gas-sensing is presented. This structure, employed as a Schottky diode, utilizes sol-gel prepared Ga2O3-ZnO layer as the reactive insulator. The sensor has been exposed to propene gas, which lowers the barrier height of the diode. The responses were stable and repeatable at operating temperatures between 300 and 600°C. The response to propene in different ambients was examined. The effect of diode bias has been investigated by analyzing the sensors response to various propene concentrations when held at constant currents of 2 and 8 mA. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Near-field optical sensors for particle shape measurements

    Page(s): 646 - 651
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (583 KB) |  | HTML iconHTML  

    Two new optical particle shape sensors are introduced. By placing them directly in the near-field of the particle projection (Fresnel region), no lenses or additional optical components are required to obtain particle images. Besides size information, accurate shape information is also obtained. Simulations show that distortion by diffraction is limited and can be reduced even further. Both static and dynamic measurements have been performed, which show that the sensors work as predicted by theory. The sensors have been developed to be applied in a microfluidic cytometer. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Integrated smart sensor networking framework for sensor-based appliances

    Page(s): 579 - 586
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (326 KB) |  | HTML iconHTML  

    This paper presents an integrated, sensor networking framework stemming from the IEEE 1451 smart transducer interface standard. This object-based networking model is complemented by the Virtual Interface Architecture (VIA), a Compaq-Intel-Microsoft approach to Internet messaging, and by the Internet Protocol (IP) multicast communication, mediating efficient and unified access from Internet to smart sensors. An application of networked sensors that offers a reusable design pattern for a class of sensor-based appliances is analyzed. The kernel of the paper focuses utilization of this framework for a computer-based pressure measurement systems developing environment as a real-world project while stressing smart pressure sensor and Internet connectivity architectures. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • LGX pure shear horizontal SAW for liquid sensor applications

    Page(s): 554 - 561
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (582 KB) |  | HTML iconHTML  

    This paper reports predicted and measured properties of the pure shear horizontal (SH) mode for the LGX family of crystals, which includes langasite (LGS), langanite (LGN), and langatate (LGT). These crystals are of the trigonal class 32 group, as quartz, and they exhibit the SH symmetry type uncoupling for the Euler angles (0°, θ, 90°). This surface acoustic mode, also known as surface transverse wave (STW), is especially attractive for liquid sensing due to the moderate damping observed in liquid or viscous environments. Numerical and experimental propagation data presented for the SH mode on LGX (0°, θ, 90°) includes phase velocity (vp), electromechanical coupling coefficient (K2), temperature coefficient of delay (TCD), fractional change in frequency with respect to temperature (Δf/fo), penetration depth, metal strip reflectivity, and excitation of spurious plate modes as a function of θ. High electromechanical coupling and zero temperature coefficient of delay (TCD) along LGX Euler angles (0°, θ, 90°), θ between 10° and 25°, with penetration depths comparable to surface acoustic wave (SAW) devices are disclosed. In particular, along LGT (0°, 13.5°, 90°), the experimental results reported with resonators and delay line structures verify the high electromechanical coupling (0.8%) for a SH SAW mode, about 10 times stronger than the 36° Y rotated quartz SH orientation, and the existence of zero TCD around 140°C. The phase velocity of 2660 m/s is within 0.2% of the calculated value, which is about 55% below the phase velocity of 36° Y quartz, thus leading to smaller STW devices. The penetration depth of 6.5 wavelengths is eight times more shallow than 36° Y quartz, thus providing significant SH mode energy trapping close to the surface. With such positive predicted and measured coupling and propagation characteristics, these orientations are appropriate for the fabrication of high coupling, zero TCD, smaller, and highly sensitive STW devices for filtering, frequency control, and liquid sensor applications. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • High-performance photo detector for correlative feeble lighting using pixel-parallel sensing

    Page(s): 640 - 645
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (902 KB) |  | HTML iconHTML  

    We have developed a high-performance photo detector, which can detect a feeble projected light with pulse modulation in strong ambient light from other light sources. It is useful to expand the application field of the three-dimensional measurement system using a light-section method. A correlation circuit and a current-mode suppression circuit of constant illumination allow high sensitivity, high selectivity, and adaptive suppression of background illumination. A logarithmic-response circuit is employed to avoid saturation for wide dynamic ranges. The photo detector can quickly detect the modulated light by pixel-parallel sensing. It has advantages for some applications which require availability in various background illuminations and safe light projection for human eyes. The photo detectors have been developed and successfully tested. The high sensitivity under -18-dB signal-to-background ratio (SBR) is realized over the 47.2-dB dynamic range. The minimum SBR is -22.8 dB and the potential frame rate is 2000 fps. In addition, the photo detector shows high selectivity in a multiple-lighting system due to the suppression of orthogonally modulated light. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

Aims & Scope

The IEEE Sensors Journal is a peer-reviewed, monthly online/print  journal devoted to sensors and sensing phenomena

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Krikor Ozanyan
University of Manchester
Manchester, M13 9PL, U.K.