Showing papers on "Data acquisition published in 1995"

Introduction to Engineering Experimentation

Abstract: 1. Introduction. 2. General Characteristics of Measurement Systems. 3. Measurement Systems with Electrical Signals. 4. Computerized Data Acquisition Systems. 5. Discrete Sampling and Analysis of Time-Varying Signals. 6. Statistical Analysis of Experimental Data. 7. Experimental Uncertainty Analysis. 8. Measurement of Solid-Mechanical Quantities. 9. Measuring Pressure, Temperature and Humidity. 10. Measuring Fluid Flow Rate, Fluid Velocity, Fluid Level, and Combustion Pollutants. 11. Dynamic Behavior of Measurement Systems. 12. Guidelines for Planning and Documenting Experiments. Appendix A: Computational Methods for Chapter 5. Appendix B: Selected Properties of Substances. Glossary. Answers to Selected Problems. Index.

Continuous radial data acquisition for dynamic MRI

Abstract: Since image acquisition times in MRI have been reduced considerably over recent years, several new important application areas of MRI have appeared. In addition to pure static anatomic information, the evolution of a dynamic process may be visualized by a sequence of temporal snapshots of the process acquired within a short time period. This makes applications like interactive or interventional MRI as well as the acquisition of additional functional information feasible. For high temporal resolution, all these applications require a quasi real-time image acquisition during the time the interaction or dynamic process evolves. We present an approach to real-time imaging using a continuous radial acquisition scheme. The intrinsic advantages of radial or projection reconstruction (PR) techniques are used to minimize motion-related image distortions. Modifications of the acquisition scheme as well as dedicated reconstruction techniques are used to further reduce the temporal blurring due to the finite acquisition time of one entire data set in our approach. So far we have used this technique for the visualization of active joint motion.

Semiconductor gamma-ray camera and medical imaging system

Abstract: A high-energy photon imaging system including an imaging head, a signal processor, a data acquisition system and an image processing computer. The imaging head includes a detector comprising a plurality of closely-packed detection modules. Each detection module comprises a plurality of detection elements mounted to a circuit carrier. The detection elements produce electrical pulses having amplitudes indicative of the magnitude of radiation absorbed by the detection elements. The circuit carrier includes channels for conditioning and processing the signals generated by corresponding detection elements and for preparing the processed signals for further processing by a signal processor. Each conditioning and processing channel stores the amplitudes of the detection element electrical pulses exceeding a predetermined threshold. The detection modules employ a fall-through circuit which automatically finds only those detection elements that have a stored pulse amplitude exceeding the threshold. The fall-through circuit searches for the next detection element and associated channel having a valid event. The signal processor performs diagnostics, gain normalization, and response efficiency normalization functions. The data acquisition system controls the acquisition and processing of data received from the conditioning and processing channels, produces image data based upon the data in a format that is compatible with existing imaging cameras, and transmits the data to the image processing computer. The image processing computer formulates images based upon the processed signals and displays the formulated images on a display device.

Controlled-root formulation for digital phase-locked loops

Abstract: In a new formulation for digital phase-locked loops, loop-filter constants are determined from loop roots that can each be selectively placed in the s-plane on the basis of a new set of parameters, each with single and direct physical meaning in terms of loop noise band, width root-specific decay rate, or root-specific damping. Loops of first to fourth order are treated in the continuous-update approximation (B/sub L/T/spl rarr/0) and in a discrete-update formulation with arbitrary B/sub L/T. Deficiencies of the continuous-update approximation in large-B/sub L/T applications are avoided in the new discrete-update formulation. A new method for direct, transient-free acquisition with third- and fourth-order loops can improve the versatility and reliability of acquisition with such loops. >

An improved sine-wave fitting procedure for characterizing data acquisition channels

Abstract: This paper presents a new sine-wave fitting procedure for characterizing data acquisition channels and analog-to-digital converters. It overcomes most of the problems encountered with the classical three- or four-parameter sine-wave fitting procedure described in IEEE Standard 1057. The stochastic properties of the new procedure are thoroughly analyzed. Its performance is illustrated by simulations and measurements with a high-frequency sampling scope.

Recent developments in data-acquisition and processing on the oxford scanning proton microprobe

Abstract: A new data acquisition system has been developed for the Oxford SPM facility. This is based on a single PC-compatible computer with a custom designed interface unit and permits the recording of several channels of pulsed detector data together with x and y scanning voltages, beam charge and deadtime. In addition, the system will also control the beam position allowing the generation of irregular scan areas, line scans at any angle and the selection of point analyses using the mouse. The hardware and software of the system are described and some examples of data collected using the system are presented. One problem of quantitative microanalysis using focused beam PIXE is the fact that the local matrix composition and secondary electron emission characteristics may change on a scale comparable with the beam size across the sample. This leads to uncertainties in the measured charge (especially at the low currents found in microbeams) and local self-absorption correction which can introduce significant inaccuracy into the analysis. This problem has been largely solved at Oxford by the simultaneous use of RBS analysis. The shape of the RBS spectrum yields the local matrix composition and its area gives a measure of the total charge, so that the dependence on precise charge measurement is much reduced. This “Q factor” technique is described in detail and it is shown that once the system has been calibrated routine standardless accuracy of the order of 5–10% can be obtained.

Motion correction of PET images using multiple acquisition frames

Abstract: Positron emission tomography (PET) is a relatively lengthy brain imaging method. Because it is difficult for the patient to stay still during the data acquisition, head motion during scans are a source of image degradation. To reduce the degradation, a simple data acquisition technique is described. This technique associates the incoming data with the real-space position of the head. It consists of constantly monitoring the head position during PET studies and comparing the head position to the initial head position associated with the current acquisition frame. Every time the maximum RMS displacement within the field of view (FOV) is larger than a specified threshold value, the data acquisition system starts acquiring the data into a new frame. A complete study is then acquired over several frames. The number of frames required depends on the motion of the head during the study and on the threshold value. At the end of the study all the acquired frames are reconstructed independently and each image is rotated and translated according to its associated initial head position. When these images are added together, it will produce a final image with fewer motion artefacts.

Automated shimming at 1.5 T using echo-planar image frequency maps.

Abstract: Using echo-planar imaging, we developed an automated image-based procedure to shim the static (B0) field. Our method uses the rapid acquisition capability of echo-planar imaging to collect the required frequency data rapidly, rendering the shim data acquisition time negligible in comparison with the total study time. We address image distortion issues involved in echo-planar imaging acquisition of the data and formulate analytic methods for arriving at an optimal shim for the NMR imaging experiment in a single iteration. We investigated the use of cost functions other than least-squares (Chebychev, high-order numeric) and found that choice between the cost functions we tested was irrelevant to resultant image quality, at least when used in conjunction with low-order shims. With appropriate integration, the method has become routine practice for investigators at our laboratory.

LabVIEW: A software system for data acquisition, data analysis, and instrument control

Abstract: Computer-based data acquisition systems play an important role in clinical monitoring and in the development of new monitoring tools. LabVIEW (National Instruments, Austin, TX) is a data acquisition and programming environment that allows flexible acquisition and processing of analog and digital data. The main feature that distinguishes LabVIEW from other data acquisition programs is its highly modular graphical programming language, “G,” and a large library of mathematical and statistical functions. The advantage of graphical programming is that the code is flexible, reusable, and self-documenting. Subroutines can be saved in a library and reused without modification in other programs. This dramatically reduces development time and enables researchers to develop or modify their own programs. LabVIEW uses a large amount of processing power and computer memory, thus requiring a powerful computer. A large-screen monitor is desirable when developing larger applications. LabVIEW is excellently suited by testing new monitoring paradigms, analysis algorithms, or user interfaces. The typical LabVIEW user is the researcher who wants to develop a new monitoring technique, a set of new (derived) variables by integrating signals from several existing patient monitors, closed-loop control of a physiological variable, or a physiological simulator.

Meter placement for real-time monitoring of distribution feeders

Abstract: This paper identifies the data requirements for real-time monitoring and control of distribution systems. It points out that in addition to having supervisory control and data acquisition on switches and control equipment, methods are needed to obtain an accurate estimation of data needed for feeder automation functions. A meter placement method is proposed for this purpose. It is shown that the measurements from such a metering scheme can be used with a state estimator to provide the real-time data needed for real-time monitoring of a distribution system.

Method and apparatus for optical interferometric measurements with reduced sensitivity to vibration

Abstract: A method and system for providing interferometric measurements having reduced sensitivity to vibrations. An interference pattern from an interferometer (35) is amplitude split into first and second interferograms and imaged onto first and second detectors (10,11), respectively, such as CCD cameras (10,11). The two cameras (10,11) have different data acquisition rates, such as a fast:slow camera ratio of at least 2:1, and are so disposed such that the image fields substantially overlap and are synchronized with each other so that the frame integration periods are identical and overlap in time. During data acquisition a phase shifter (45) changes the phase difference between the beams in the interferometer (35) while data from both cameras (10,11) is taken by a frame grabber (15) and saved in a computer (25). During data analysis, the phase at each image point on each frame of the fast data set is calculated by the computer (25), with the phase difference between interferograms in the slow data set being determined from the phases derived from the fast data set and with the slow data set then being analyzed for phase at each image point using the measured phase increments.

A real-time electrical impedance tomograph

Abstract: Electrical properties of tissues in the human body can be imaged using a technology known as Electrical Impedance Tomography. In this modality, sinusoidal electrical currents are applied to the body using electrodes attached to the skin, and voltages that are developed on the electrodes are measured. Using these data, a reconstruction algorithm computes the conductivity and permittivity distributions within the body. This paper describes the reconstruction algorithm, image display algorithm, and hardware of a real-time Electrical Impedance Tomograph known as the Real-Time Imaging System. The reconstruction algorithm, executed by a commercially available coprocessor board that resides in a 386-based personal computer, is a modification of the Newton's One Step Error Reconstructor (NOSER) that minimizes algorithm execution time by precomputing many quantities. The image display algorithm, also executed by the coprocessor board, maps the output of the reconstruction algorithm into an image which is displayed using a video graphics board. The architecture of the system and execution times of algorithms implemented by the system are discussed. Using the continuous data acquisition mode of the Real-Time Imaging System, data from the thorax of a normal human subject were collected. Admittivity changes in the chest, as a result of respiration and the cardiac cycle, are presented. Data that were collected from the leg of a normal subject are shown which demonstrate capabilities of the triggered data acquisition mode of the system, allowing data acquisition synchronization with an electrocardiogram. >

A video-based system for acquiring biomechanical data synchronized with arbitrary events and activities

Abstract: A video-based data acquisition and interactive multimedia data extraction system are described for measuring and synchronizing large quantities of biomechanical analog data with arbitrary events and activities. Analog signals from up to 32 channels are digitized, frequency-shift key (FSK) coded, and recorded directly onto the audio tracks of a video tape in synchronization with the video information. The data acquisition system includes an A/D converter that digitizes up to 16 multiplexed channels of 8-b data at a fixed sample rate between 60 and 960 Hz, and an FSK modem that transfers the data onto one of two VHS high fidelity (20 Hz-20 kHz bandwidth) audio tracks. Twenty megabytes of digitized data and time codes, along with associated video and normal audio are contained on a conventional 120-min video tape. An analyst interactively reviews the video tape off-line using a computer-controlled VCR and identifies specific events that divide arbitrary activities into time segments. The computer automatically extracts the biomechanical data corresponding to each time segment for further processing or analysis. This system is useful for ergonomics, gait analysis, sports medicine, sleep laboratory, biomechanics, or any application where complex visual events are synchronized with low-frequency analog data. >

Computer controlled, 3-CCD camera, airborne, variable interference filter imaging spectrometer system

Abstract: A spectrally-filtered, miniature, imaging spectrometer system for airborne remote sensing data acquisition with a two dimensional field of view. Synchronized CCD-imager sensor modules or cameras are aligned to a common field of view. One sensor module has a visible range variable interference filter on its surface and a second module has a near-infrared range variable interference filter on its surface. Video data from the three sensor modules is combined and recorded on a single analog or digital recorder. Futher, such video data is monitored by a computer and used to control the shutter speed of each of the three sensor modules. Wavelength spectral image data and directional spectral image data are acquired by a single pass over a target area. Post-processing of such data produces reconstructed track-recovery-images extracted from a sequence of video frames for the spectral regions of interest at a fixed column position to produce multiple bands of monochrome images.

Dynamic three-dimensional echocardiographic assessment of intracardiac blood flow jets.

Abstract: Transthoracic dynamic 3-dimensional reconstruction of the heart with tissue depiction has been proved to be feasible when using various methods of data acquisition. The same method can theoretically be applied to color Doppler flows to generate dynamic 3-dimensional images of intracardiac blood flow jets. To explore the feasibility of this approach, we studied 41 patients with various valvular disorders or intracardiac shunts. We acquired sequential 2-dimensional images along with color Doppler information using rotational scanning from a transthoracic or a subcostal window. Images were digitized and processed for 3-dimensional reconstruction using dedicated software. After adequate segmentation, the flow jets were displayed in 3 dimensions in a gray scale format. With use of this approach, 3-dimensional reconstruction of color Doppler flows was possible in all but 1 patient. Still frames allowed immediate appreciation of the shape of the jets, their location in the cardiac chambers, and their size related to that cavity. Dynamic display was even more striking by showing the flow in real time. Dynamic 3-dimensional images enabled visualization of flow jets in projections not available in conventional color flow Doppler, looking directly at the views of shunt and regurgitant flows, and also permitted 3-dimensional delineation of flow convergence zones. We conclude that dynamic visualization of various intracardiac flows in 3 dimensions using transthoracic echocardiography is possible. It provides a better understanding of the shape and size of the jets, and can potentially aid in flow quantification by displaying the actual shape of flow convergence regions.

Electric vehicle monitoring system

Abstract: An Electric Vehicle Monitoring System (EVMS) for measuring the performancef an electric vehicle. The preferred embodiment of the system comprises: (1) a variety of sensors for obtaining data on vehicle performance and operating parameters; (2) a digital dashboard display providing the vehicle operator with information on vehicle operating parameters; (3) a data acquisition system for collecting the data from the sensors and converting the data to digital format; and (4) a processing unit in the form of a removable, portable or notebook computer used for storing, evaluating and providing reports of the digital format data. The EVMS is adapted for use in a vehicle specifically designed for electric propulsion or for use in an internal combustion engine vehicle converted to electrical power use. The sensors include voltmeters, ammeters, thermocouples, optical shaft encoders and an inclinometer and provide data to both the operator display and the data acquisition system. The operator display includes bargraphs for current draw, motor and battery temperature, accessory battery voltage, main battery voltage or "fuel level" and alphanumeric displays for vehicle speed, distance traveled, trip meter and transmission gear indicator.

Guide to Data Acquisition and Analysis

Abstract: This chapter should provide a first guide to the acquisition and analysis of patch-clamp data Except for the sections on single-channel analysis, the procedures and considerations also hold for data obtained using other voltage-clamp methods. It is assumed that the reader is familiar with the standard methods and terminology of patch-clamp electrophysiology. Because many of the problems that arise during data analysis can be avoided by a proper design of the experiment, including data acquisition, we start by deriving some criteria that should be considered before actually starting to record data.

Device data acquisition

Abstract: Data samples are obtained from a control device while in use to control a material process. Selected ones of these samples are stored which represent results of operating the device over portions of its characteristics, and they are selectively combined to provide an indication of the complete device characteristics. Selected such data samples are used provide information concerning selected control device parameters based on the device characteristics.

Correction and automated analysis of spectral and imaging data

Abstract: Using regression analysis, n-dimensional spectral and imaging data from sources including Nuclear Magnetic Resonance or Electron Spin Resonance spectrometers, can be automatically analyzed and the data acquisition equipment or the data itself can be corrected for various determined types of distortion. The method allows correction of, for example, signal drift, sample saturation, removal of phase, baseline and shim distortions and allows removal of unwanted signals from the data. From ratios of determined parameter and error values signals can be distinguished from noise-related responses and using Monte Carlo simulations the corresponding signal detection probabilities can be derived. With the model of an n-dimensional signal, a parametric description of the dataset can be obtained with parameter and error values which truly reflect signal overlap and mutual parameter correlations. From this parametric description higher-level interpretations of the data, such as spin systems and related signal patterns, can be derived efficiently.

Servers in SCADA applications

Abstract: Data acquisition and supervisory control and data acquisition (SCADA) systems have evolved from mainframe-based systems to multilevel tiered systems to flat client-server architecture. This paper examines the necessity for this evolution and the technology that spurred it on. A rod mill is discussed as a case study.

Data acquisition device

Abstract: A data acquisition device includes a receiver operable to receive a stream of data, a first input device operable to supply an identifier to identify data from the stream of data received by the receiver, a second input device operable to produce a signal indicative that data from the stream of data received by the receiver is valid, and storage operable to store the identifier supplied by the first input device in combination with data from the stream of data received by the receiver. The data acquisition device also includes a controller operable to operate the device in a monitor mode in which data from the stream of data received by the receiver is monitored and an actual measurement mode in which data from the stream of data received by the receiver is stored in the storage along with the identifier supplied by the first input device. The controller switches operation of the device from the monitor mode to the actual measurement mode when the signal from the second input device indicates that the data is valid.

Design of a multispectral, wedge filter, remote-sensing instrument incorporating a multiport, thinned, CCD area array

Abstract: The next generation Wedge Imaging Spectrometer (WIS) instruments currently in integration at Hughes SBRD incorporate advanced features to increase operation flexibility for remotely sensed hyperspectral imagery collection and use. These features include: a) multiple linear wedge filters to tailor the spectral bands to the scene phenomenology; b) simple, replaceable fore-optics to allow different spatial resolutions and coverages; c) data acquisition system (DAS) that collects the full data stream simultaneously from both WIS instruments (VNIR and SWIR/MWIR), stores the data in a RAID storage, and provides for down-loading of the data to MO disks; the WIS DAS also allows selection of the spectral band sets to be stored; d) high-performance VNIR camera subsystem based upon a 512 X 512 CCD area array and associated electronics.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Visual masking and the design of magnetic resonance image acquisition

Abstract: This paper presents novel data acquisition schemes for improving the quality of magnetic resonance images (MRI) These approaches determine the number of times that k-space (frequency domain) samples have to be acquired and averaged to form an MRI image, by taking into account the characteristics of the human visual system and the location in k-space of the data samples They lead to dramatic reductions in imaging time (by a factor of 8 to 10) with no reduction in image quality Alternatively, they produce higher quality imagery using the same amount of imaging time as conventional approaches

Multiple weapon firearms training method utilizing image shape recognition

Abstract: A method and apparatus for simultaneously training multiple trainees in the use of simulated weapons, which method defines a set of image shapes and assigns each image shape to a different simulated weapon capable of generating a light beam, at a selected wavelength, having the assigned image shape. By collecting data under control conditions and evaluating a set of parameters that uniquely identifies each image shape and by comparing the resulting "control parameters" to the same set of parameters evaluated under training conditions (thereby, producing "on-line parameters") each image shape produced during a training session is identified and associated with a simulated weapon. The method enables an expanded number of trainees to be simultaneously trained, by employing the same set of image shapes produced and detected at different wavelengths. In accordance with the preferred embodiment, the apparatus includes a plurality of simulated weapon having a light source, a reflective surface, a light data acquisition assembly, and a controller to analyze and compare collected data. The light data acquisition assembly comprises a rasterizing sensor (i.e., a CCD camera), wavelength filter, and a data acquisition interface has a plurality of counters which convert pixel intensity and location data into a category of data, including position, length and intensity, for each segment of an image shape for subseqent receipt by the controller.

Continuous recording and stochastic analysis of PD

Abstract: We describe the design and use of a digital partial discharge (PD) data recording system capable of continuous real-time recording of PD pulse trains. The recording system consists of a custom two-channel PD digitizer coupled to a personal computer via a 10-bit parallel interface. The digitizer is under software control with the resulting data being stored in binary files on the computer's hard disk. The stored data subsequently are subjected to stochastic analysis using appropriate computer software. Because all data are retained and the computer provides the desired stochastic analysis of data files, the new system is well suited to investigate non-stationary PD behavior such as encountered in aging studies. By way of illustration, the new system was used to determine the time-varying stochastic behavior of ac-generated PD from point-to-dielectric gaps in air where the insulation material was cast epoxy with aluminum oxide filler. The results confirm and extend previous measurements made with an analog stochastic analyser. With these sample results, we demonstrate how the system allows detailed stochastic analyses not possible with data obtained from existing conventional PD measurement systems. >