Showing papers in "IEEE Transactions on Instrumentation and Measurement in 1997"
TL;DR: In this article, an enhanced model for an open-ended coaxial probe used for making permittivity measurements is presented, including details of the error correction and curve fitting techniques.
Abstract: An enhanced model for an open-ended coaxial probe used for making permittivity measurements is presented. A permittivity measurement system consisting of the coaxial probe and a network analyzer is described including details of the error correction and curve fitting techniques. Determination of the percent dissolved solids in fructose solutions from permittivity measurements is presented as example of the usefulness of the coaxial probe/network analyzer measurement system.
295 citations
TL;DR: A new design of a time-to-digital converter (TDC) implemented on an FPGA chip with amorphous antifuse structures is presented and the output from the delay line is obtained directly in "1-out-of-N" code and then converted to 6-bit natural binary.
Abstract: A new design of a time-to-digital converter (TDC) implemented on an FPGA chip with amorphous antifuse structures is presented. Time coding with 200-ps resolution (LSB), 10-ns range, and very short conversion time is realized by two tapped delay lines working in-a differential mode. Thanks to the local feedback loops, the output from the delay line is obtained directly in "1-out-of-N" code and then converted to 6-bit natural binary. Within the temperature range from 0/spl deg/C to 45/spl deg/C, the time offset at the output is constant, the resolution changes by /spl plusmn/0.02 LSB, and the offset-corrected integral linearity error is less than 1 LSB.
165 citations
TL;DR: In this paper, a model-based method for sound localization of concurrent and continuous speech sources in reverberant environment was presented, where a new algorithm adopted from the echoavoidance model of the precedence effect was used to detect the echo-free onsets by specifying a generalized pattern of impulse response.
Abstract: This paper presents a model-based method for sound localization of concurrent and continuous speech sources in reverberant environment. A new algorithm adopted from the echo-avoidance model of the precedence effect was used to detect the echo-free onsets by specifying a generalized pattern of impulse response. Fine structure time differences were calculated from the zero-crossing points in different microphones. They were integrated into an azimuth histogram by the restrictions between them. Two sound sources were localized in both an anechoic chamber and a normal room which has walls, floor, and ceiling made of concrete. The time segment needed for localization was 0.5-2 s and the accuracy was a few degrees in both environments.
100 citations
TL;DR: Measurements of railway disc brake temperature by on-disc SAW sensors and wireless measurement of the air pressure in the tires of road vehicles in motion are presented.
Abstract: Wirelessly interrogated passive surface acoustic wave (SAW) sensors for measurements in a rough environment are shown. These can be applied when remote readout is necessary and other sensors cannot withstand heat, dirt, mechanical vibration, and/or electromagnetic interference. Applications of passive SAW sensors for sensing tasks, especially in vehicles are discussed. The implementation of SAW sensors for measurements of torque and speed of revolution on transmission shafts is discussed. We present measurements of railway disc brake temperature by on-disc SAW sensors and wireless measurement of the air pressure in the tires of road vehicles in motion. The applied SAW sensors, the corresponding interrogation systems and an algorithm for signal processing are described. Estimations of measurement errors and results of measurements are discussed.
97 citations
TL;DR: The results shown have been chosen among those obtained throughout the last three years by testing clerks of digital switching exchanges, clocks for synchronous digital hierarchy equipment, and state-of-the-art stand-alone slave clocks for synchronization networks and represent a survey of the actual performance of clocks currently deployed in telecommunications networks.
Abstract: Clock stability characterization and measurement for telecommunications pose peculiar issues and requirements. This paper aims to provide an overview on this subject. After briefly recalling the background work, the key features and issues of clock stability characterization and measurement in telecommunications are described. The timing signal reference model and the stability quantities adopted in the new international standards are introduced and the impact of the measurement configuration and of the time error sampling period on their behavior are elucidated. The measurement of clock stability in telecommunications is then addressed, and a standard practical measurement procedure is outlined. Several measurement results are provided to support the concepts expounded with experimental evidence. The results shown have been chosen among those obtained throughout the last three years by testing clerks of digital switching exchanges, clocks for synchronous digital hierarchy (SDH) equipment, and state-of-the-art stand-alone slave clocks for synchronization networks. They thus represent a survey of the actual performance of clocks currently deployed in telecommunications networks.
90 citations
TL;DR: In this paper, a low-cost, simple, noncontact displacement sensor using the self-mixing effect inside a cw single-mode laser diode has been developed for modal analysis and defect detection.
Abstract: A low-cost, simple, noncontact displacement sensor using the self-mixing effect inside a cw single-mode laser diode has been developed for modal analysis and defect detection. The resonance frequencies of thin clamped metallic plates have been determined with a resolution of 0.2 Hz. With such targets, classic spectrum analyzers generate a measurement error up to 10% because of the weight of the accelerometer. The frequency-shift of the fundamental resonance frequency between a standard plate and the same one with a known defect can also be measured, the modal vector associated to this frequency being distorted at the place of the defect.
86 citations
TL;DR: In this paper, the position of a rotor supported in magnetic bearings is inferred from the bearing current waveform using a two-state switching amplifier which produces a substantial high-frequency switching ripple.
Abstract: A signal processing technique is presented by which the position of a rotor supported in magnetic bearings may be deduced from the bearing current waveform. The bearing currents are presumed to be developed with a two-state switching amplifier which produces a substantial high-frequency switching ripple. This ripple is demodulated using a parameter estimation technique which extracts the length of the bearing air gap while rejecting the influence of amplifier voltage and duty-cycle variation. The performance of the estimator is evaluated both by simulation and experiment. The method is demonstrated to produce a sensor with bandwidth of at least 1 kHz and acceptably low feed-through of the bearing force.
85 citations
TL;DR: In this article, an accurate technique used to measure complex permittivity and permeability of isotropic materials simultaneously has been developed by employing a flanged open-ended rectangular waveguide probe over a frequency range of 8-12 GHz.
Abstract: An accurate technique used to measure complex permittivity and permeability of isotropic materials simultaneously has been developed by employing a flanged open-ended rectangular waveguide probe over a frequency range of 8-12 GHz. Two coupled integral equations for the aperture electric field are formulated and solved numerically using Galerkin's method. A series of experiments has been conducted, and the calibration of the probe system using an adjustable shorter is explained. The inverse results on the electromagnetic (EM) properties of various materials (including solid and liquid materials) based on the measured reflection coefficients of the incident dominant mode are presented. It is also shown that the EM parameters of isotropic materials having low complex permittivities can be determined accurately, while those with higher complex permittivities cause larger measurement errors.
71 citations
TL;DR: An interface for a capacitive pressure sensor which accommodates digital encoding and linearization functions has been developed and offset and scale adjustment, and cross-parameter compensation are also possible with this architecture.
Abstract: An interface for a capacitive pressure sensor which accommodates digital encoding and linearization functions has been developed. The front-end is a switched-capacitor bridge which converts the sensor capacitance into a proportional voltage. This voltage is applied to a pulse-width modulator to be compared with a model signal generated by a digital waveform synthesizer (DWS). This model-based signal processing provides the digital equivalent of the pressure being measured. For high-yield, monolithic implementation of the interface, oversampling /spl Delta/-/spl Sigma/ demodulation techniques are used for the DWS. In addition to the digital functions, offset and scale adjustment, and cross-parameter compensation are also possible with this architecture. A prototype interface is described to demonstrate these capabilities.
70 citations
TL;DR: The solution of the nonlinear system not only minimizes the perspective transformation relations between the image points and the corresponding world coordinates, but also satisfies the orthonormality constraints on the rotational transformation.
Abstract: Camera calibration is a crucial problem for many industrial applications that incorporate visual sensing. In this paper, we compute the intrinsic and extrinsic calibration parameters in three steps. In the first step, the calibration parameters are approximated using the linear least-squares method. In the second step, we develop two alternative formulations to obtain an optimal rotation matrix from the calibration parameters computed in the first step. Further optimization of translational and perspective transformations is then performed based on the optimized rotation matrix. In the third step, a nonlinear optimization is performed to handle lens distortion. The solution of the nonlinear system not only minimizes the perspective transformation relations between the image points and the corresponding world coordinates, but also satisfies the orthonormality constraints on the rotational transformation. To assess the performance of our proposed method, the Euclidean norm of the error matrix between the calculated and the original 4/spl times/4 homogeneous transformation matrices is used as a basis for comparison with existing methods. Simulation results from applying the method show significant improvements both before and after the nonlinear optimization step.
69 citations
TL;DR: In this paper, a capacitive precision liquid-level gauge was developed, which consists of a low-cost planar electrode structure, a capacitance-controlled oscillator and a microcontroller.
Abstract: A new capacitive precision liquid-level gauge has been developed. The sensor consists of a low-cost planar electrode structure, a capacitance-controlled oscillator and a microcontroller. The device is able to measure absolute levels of conducting and nonconducting liquids with a 1 mm uncertainty over a 4 m range. The system has a high resolution of 0.1 mm at short measuring times of only 0.2 s. Slow level movements of 0.02 mm/h can be detected within 18 min.
TL;DR: In this article, two types of microwave filters, metallic powder filters and a filter using a resistive coaxial cable, were tested, and it was found that SUS304L powder of nominal 30 /spl mu/m grain size gives best result as the microwave filter for single electron tunneling (SET) experiments.
Abstract: Two types of microwave filters, metallic powder filters and a filter using a resistive coaxial cable, were tested. Attenuation of the metallic powder filters using copper or stainless steel (SUS304L) was measured at 300 K, 77 K, and 4.2 K, and it was found that SUS304L powder of nominal 30 /spl mu/m grain size gives best result as the microwave filter for single electron tunneling (SET) experiments. Attenuation of a coaxial filter, or Thermocoax with SMA connectors attached at both ends is larger at low temperatures than that at room temperatures, and the temperature dependence of the attenuation does not agree with Zorin's model. The filter arrangement in a cryostat designed for SET experiments, is also reported.
TL;DR: In this article, the dielectric permittivities of bulk samples of adult rice weevils were measured over the frequency range from 0.2 GHz to 20 GHz at temperatures from 10/spl deg/C to 65/spl dc with an open-ended coaxial line probe, network analyzer, and a sample temperature control assembly designed for the measurements.
Abstract: The dielectric permittivities of bulk samples of adult rice weevils were measured over the frequency range from 0.2 GHz to 20 GHz at temperatures from 10/spl deg/C to 65/spl deg/C with an open-ended coaxial-line probe, network analyzer, and a sample temperature control assembly designed for the measurements. Repeated measurements were highly variable, because mean sample bulk densities did not accurately reflect effective densities of the bulk rice weevil samples in the small volume of sample sensed by the coaxial-line probe. Density corrections based on earlier permittivity measurements on bulk rice weevil samples at 9.4 GHz, at known sample densities, removed much of the variability. The corrections utilized the linear relationship between the cube root of the dielectric constant and bulk density, which permitted estimates of the weevil body permittivities to be obtained with the Landau, Lifshitz, and Looyenga equation for dielectric mixtures. Estimated dielectric constants and loss factors of the insects from averages of seven different measurement sequences are presented graphically for temperatures from 15/spl deg/C to 65/spl deg/C.
TL;DR: In this article, an automated guarded bridge for calibrating multimegohm standard resistors is described, where the balanced algorithm used to estimate the calibrator setting required to obtain a null is described along with a graphical user interface.
Abstract: The implementation of an automated guarded bridge for calibrating multimegohm standard resistors is described. A guarded multimegohm bridge has been assembled with programmable dc calibrators in two of the arms allowing multiple ratios and test voltages to be remotely selected. A programmable electrometer with a resolution of /spl plusmn/3 fA in the current mode is used to measure the difference in currents flowing through the remaining two arms of the bridge consisting of unknown and standard resistors. The balancing algorithm used to estimate the calibrator setting required to obtain a null is described along with a graphical user interface (GUI) that has been written to provide flexibility to the measurement system and improve control of the instrumentation. Evaluation of the multimegohm bridge from 10 M/spl Omega/ to 1 T/spl Omega/ is reported along with a comparison of the multimegohm bridge performance to that of the existing manual and semi-automated systems that the multimegohm bridge will replace.
TL;DR: In this paper, a piezoresistive strain-gauge sensor, mounted in an array configuration, for the measurement of distributed pressures during robotic grasp applications is investigated, consisting of a 16-element test cell connected to an electronic acquisition unit that also provides temperature compensation.
Abstract: A piezoresistive strain-gauge sensor, mounted in an array configuration, for the measurement of distributed pressures during robotic grasp applications is investigated. The prototype presented consists of a 16-element test cell connected to an electronic acquisition unit that also provides temperature compensation. The structure of the tactile sensor and its principle of operation are described.
TL;DR: In this article, a transducer interface for resistive bridges is presented, where the bridge supply voltage is measured for reference purposes in small parts (piecewise measurement) which are within the range of the bridge output voltage.
Abstract: This paper presents a one-chip simple and accurate transducer interface for resistive bridges. A key part of this interface is formed by a novel dynamic voltage divider. In this divider the bridge supply voltage is measured for reference purposes in small parts (piece-wise measurement) which are within the range of the bridge output voltage. The use of an autocalibration technique, the three-signal method, eliminates influeuce of linear parameters and errors. Moreover, the effects of the nonidealities of the applied switches are also eliminated. The circuit has been realized in a 3 /spl mu/m BiCMOS process and shows an uncertainty of only 10 /spl mu/V for a bridge supply voltage of 5 V.
TL;DR: In this paper, the effects of alignment uncertainties of the NIST watt balance with respect to local gravity and the magnetic flux density of the balance have been analyzed, and potential improvements in the balance design have been identified which could ultimately lead to a reduction of that uncertainty to below 10 nW/W.
Abstract: The effects of alignment uncertainties of the NIST watt balance with respect to local gravity and the magnetic flux density of the balance have been analyzed. Techniques for measuring all quantities relevant to misalignment have been developed. The components of the relative combined standard uncertainty of the measured value of the watt due to alignment uncertainties have been reduced to 20 nW/W, and potential improvements in the balance design have been identified which could ultimately lead to a reduction of that uncertainty to below 10 nW/W.
TL;DR: A calibration method is presented which features a progressive improvement in the sensor calibrated transfer toward the desired transfer as the user proceeds from one calibration point to the next.
Abstract: Output signal handling of a smart sensor usually involves a calibration facility to correct for input-output nonidealities which comprise offset, gain errors, nonlinearity errors, and cross sensitivity. In this paper, a calibration method is presented which features a progressive improvement in the sensor calibrated transfer toward the desired transfer as the user proceeds from one calibration point to the next. The method is based on a set of mathematical formulas whereby a calibration coefficient is calculated at a selected calibration point and used to calculate a first correction of the sensor transfer curve. Further improvement in the sensor transfer is obtained by repeating the process for a second calibration point using the transfer resulting from the first calibration, without the need to review the calibration already carried out at the first point. The process can be repeated until the desired error reduction is obtained. Step by step, the calibration method builds up a polynomial transfer correction. Simulation results are shown to demonstrate the performance of the method, A software implementation of the method for two-dimensional (2-D) calibration in an 8-bit microcontroller is presented. The microcontroller with calibration program can be incorporated in a compact smart sensor system.
TL;DR: In this paper, X-ray and optical interferometry is applied to the measurement of silicon lattice spacing, and the previously reported standard deviation 0.16/spl times/10/sup -6/ has been reduced to 0.05/spltimes/10 /sup 6/
Abstract: X-ray and optical interferometry is applied to the measurement of silicon lattice spacing. The previously reported standard deviation 0.16/spl times/10/sup -6/ has been reduced to 0.05/spl times/10/sup -6/. The d(220) is 192015.593(0.01) fm after correction of lattice strain by carbon and oxygen.
TL;DR: In this paper, a new spherical Fizeau interferometer that allows the interference pattern to be evaluated by phase-stepping interferometry has been developed, which requires four phase steps of one quarter of an interference order, which are achieved by changing the air pressure inside the environmental chamber.
Abstract: In order to accurately determine Avogadro's constant, N/sub A/, the volume of a nearly perfect single-crystal silicon sphere of 1 kg mass and about 90 mm diameter is to be measured with a relative uncertainty less than 10/sup -7/. For this purpose,a new spherical Fizeau interferometer that allows the interference pattern to be evaluated by phase-stepping interferometry has been developed. This technique is based on a special algorithm for Fizeau interferences and requires four phase steps of one quarter of an interference order, which are achieved by changing the air pressure inside the environmental chamber. Uncertainties in the sub-nanometer range can be obtained by this interferometric method. The interferometer's field of view covers an angle of about 600 imaged onto an electronic camera with about 16000 pixels, so that the variation of the diameter is measured with high angular resolution. For the measurements, the sphere rests on a three-point support. The sphere can be lifted and rotated around two perpendicular axes by means of a motor-driven manipulation device, so that it can be positioned in well-defined orientations.
TL;DR: In this article, an extended cavity diode laser at 633 nm has been frequency stabilized to I/sub 2/-Doppler-free absorption signals of the P(33)6-3 transition using a third-harmonic detection technique.
Abstract: An extended cavity diode laser at 633 nm has been frequency stabilized to I/sub 2/-Doppler-free absorption signals of the P(33)6-3 transition using a third-harmonic detection technique. The frequency was measured by the beat-frequency technique with an iodine-stabilized He-Ne laser as reference. A minimum value for the two-probe relative standard uncertainty of 1/spl times/ 10/sup -11/ (5 kHz) is reached after 100 s. We also report measurements of the hyperfine splittings of the P(33)6-3 transition and laser frequency dependence on modulation amplitude and iodine pressure.
TL;DR: In this article, a bias control circuit that provides output current amplification, transient suppression, and submicrosecond settling time is used with both superconductor-insulator-superconductor (SIS) and SNS junction arrays for fast, automated measurements of A/D converter linearity, a test for subnanovolt accuracy, waveform synthesis, and a preliminary measurement of the ac-dc difference of a thermal voltage converter.
Abstract: Progress toward a Josephson voltage standard for fast dc measurements and accurate ac waveform synthesis is described. A superconductor-normal-superconductor (SNS) junction process is used to make 5 mA critical current arrays with up to 32 768 junctions. With rf excitation at 11 GHz these arrays generate milliampere constant-voltage steps. A bias control circuit that provides output current amplification, transient suppression, and submicrosecond settling time is used with both superconductor-insulator-superconductor (SIS) and SNS junction arrays for fast, automated measurements of A/D converter linearity, a test for subnanovolt accuracy, waveform synthesis, and a preliminary measurement of the ac-dc difference of a thermal voltage converter.
TL;DR: In this paper, a new current loop analog measurement circuit topology is presented that significantly outperforms the classic Wheatstone bridge in many instrumentation, measurement, and control applications using active subtraction as the key enabling technology.
Abstract: A new current loop analog measurement circuit topology is presented that significantly outperforms the classic Wheatstone bridge in many instrumentation, measurement, and control applications. Using active subtraction as the key enabling technology, the new current loop can provide greater accuracy with less excitation power and fewer connecting wires. Several sensor elements can exist in the same current loop with their independent and combined outputs available simultaneously. Measurement functions beyond what an equivalent Wheatstone bridge can provide have been accomplished. The limitations of the Wheatstone bridge are recalled and the new current loop theory is presented along with test data acquired using an elementary single component active subtractor.
TL;DR: In this article, the frequency of the 5s /sup 2/S/sub 1/2/-4d/sub 5/2/ clock transition of a single Sr ion confined in a Paul trap was measured.
Abstract: We have measured the frequency of the 5s /sup 2/S/sub 1/2/-4d /sup 2/D/sub 5/2/ clock transition of a single Sr ion confined in a Paul trap. A diode laser locked to an ultrastable Fabry-Perot (F-P) cavity was used to probe the transition with a resolution of 3.5 kHz. The absolute frequency was determined from heterodyne measurements referenced to an iodine stabilized HeNe laser and a CO/sub 2/ laser yielding a value for the S-D transition of (444 779 043 963/spl plusmn/30) kHz. This work could lead to the development of a new optical frequency standard at 674 nm.
TL;DR: This paper presents a high-performance (i.e., high-precision and high-speed) algorithm to estimate the four parameters of a sinewave from a sample data record and proposes a frequency estimator that turns the nonlinear estimation problem into a linear one.
Abstract: Sinewave fit is a fundamental task in many test and measurement systems. The characterizations of analog-digital converters and digital oscilloscopes are two examples. In this paper, we present a high-performance (i.e., high-precision and high-speed) algorithm to estimate the four parameters of a sinewave from a sample data record. By the use of trigonometric identity, we propose a frequency estimator that turns the nonlinear estimation problem into a linear one. Thus, the difficulty of the traditional nonlinear least-squares sinewave fit method is attenuated. The total least-squares method is used to estimate four parameters of a sinewave in order to minimize the estimation errors in the sense of l/sub 2/ norm. Simulation results exhibit that the proposed method gives superior performance over traditional ones and achieves excellent estimation of the true resolution of the simulated ideal ADC. This new algorithm is noniterative and gives swift and consistent results.
TL;DR: In this article, the authors describe the construction of four probes adjusted for fast transient monitoring in 123 kV SF/sub 6/ insulated substations, with the primary requirement being the ability to monitor without distortion very fast transients containing frequencies up to 200 MHz.
Abstract: This paper describes the construction of four probes adjusted for fast transient monitoring in 123 kV SF/sub 6/ insulated substations. The primary requirement was the ability to monitor without distortion very fast transients containing frequencies up to 200 MHz. The measuring system was tested and calibrated with the help of computer modeling techniques. The verified experimental apparatus was then used for testing and calibrating the measuring probes. During the test, various effects on the measuring system characteristics were analyzed with respect to materials used for the components of the system.
TL;DR: Experimental results show that the self-calibration is relatively effective in reducing the influences of the geometrical errors and pattern errors in a smart capacitive angular-position sensor.
Abstract: A self-calibration technique for capacitive position sensors, based on the use of a microcontroller is presented. This technique offers a good trade-off between the memory size of the microcontroller and the algorithmic complexity. The application of this technique for self-calibration of the inaccuracy caused by the geometrical errors and pattern errors in a smart capacitive angular-position sensor is discussed. This self-calibration technique doesn't need any accurate reference. Experimental results show that the self-calibration is relatively effective in reducing the influences of the geometrical errors and pattern errors of the sensor. The reduction of the inaccuracy of the smart capacitive angular-position sensor amounts to more than a factor of two.
TL;DR: In this article, a seven-junction electron pump was developed for use in a new standard of capacitance based on measuring the voltage produced when a known charge is placed on a capacitor.
Abstract: We have developed a seven-junction electron pump for use in a new standard of capacitance based on measuring the voltage produced when a known charge is placed on a capacitor. This new pump, with an error per pumped electron of 15/spl times/10/sup -9/, is about 30 times more accurate than a five-junction pump made previously at NIST. By careful design of the pump geometry, we have reduced the effect of cross capacitance and simplified device operation. Our fabrication recipe produces small, stable tunnel junctions relatively quickly and reliably. We have developed a method of tuning the pump for highly accurate electron counting. This tuning can be quickly repeated whenever fluctuations in background charges degrade accuracy.
TL;DR: In this paper, a six-port reflectometer is implemented in monolithic microwave integrated-circuit (MMIC) technology using non-matched diode detectors with a high input impedance.
Abstract: This paper presents a new structure for a six-port reflectometer which due to its simplicity can be implemented very easily in monolithic microwave integrated-circuit (MMIC) technology. It uses nonmatched diode detectors with a high input impedance which are placed around a phase shifter in conjunction with a power divider for the reference detector. The circuit has been fabricated using the F20 GaAs process of the GEC-Marconi foundry and operates between 1.3 GHz and 3.0 GHz.
TL;DR: In this paper, an analysis of the crosstalk between the current source and the photoelectric receiver of a heterodyne phase-shift laser range finder has been presented for the measurement of distances of 1 m to 10 m.
Abstract: A heterodyne phase-shift laser range finder has been developed for the measurement of distances of 1 m to 10 m. An analysis of the crosstalk between the current source and the photoelectric receiver of this device permits prediction of the accuracy of the setup. For example, when the amplitude of the crosstalk is proportional to the modulation frequency and for a given photoelectric signal-to-induction ratio of 30 at 10 m, the maximum corresponding error is about 5 cm. To determine the magnitude of the crosstalk, we propose a model taking into account that the amplitude and the phase-shift of the induced signal depend on whether the coupling is inductive or capacitive. Crosstalk modeling shows that very slight inductive or capacitive coupling is sufficient to affect distance measurement.