Showing papers on "Data acquisition published in 1988"

Fast MRI data acquisition using multiple detectors

Abstract: We present a novel imaging procedure using multiple receiver coils. This circumvents the sequential acquisition of signals required by conventional imaging strategies. The advantage of this technique over existing subsecond imaging techniques is that (a) contrast can be maintained and (b) there is no magnetic field gradient switching involved.

Data acquisition systems for linear and area X-ray detectors using delay line readout

Abstract: Digital systems for fast readout of linear and area position sensitive detectors based on commercially available CAMAC modules are described. The first version of the system has been used extensively for synchrotron radiation work carried out at the EMBL outstation in Hamburg during the last five years. A second system allowing measurements at count rates up to 600 kHz on a continuous source has been recently installed. An overview of the complete acquisition and information processing system is also given.

Online valve diagnostic monitoring system

Abstract: An online valve monitoring system senses operational characteristics of a valve and provides a diagnosis of aberrations in the characteristics. Sensors, coupled to a valve, supply sensor signals as output to a data acquisition system to be transmitted to a remote location. An I/O processor at the remote location receives the sensor signals and a diagnostic processor extracts characteristic features from the sensor signals as deviations from baseline data for the valve. An expert system applies a rule base to the characteristic features individually or in combination to diagnose the causes of the deviations. Use of multiple sensors increases the confidence of the diagnosis which can be immediately communicated to an operator and used for scheduling maintenance of the valve. Use of this diagnosis and the trend line of historical data permits scheduling of preventive maintenance.

Data communications system

Abstract: A data communications system utilizes computer control at central and remote locations to provide general data acquisition and control functions as part of a cable television network The data system includes a central data processor communicating with a plurality of remote data processors, each of which in turn interrogates, monitors and controls a plurality of groups of remote terminal unit Each terminal unit includes a variety of security monitoring devices as well as other data generating apparatus useful in process control and data retrieval functions Each terminal unit communicates with its remote data processor concerning the status of the security devices and receives commands from the remote data processor to carry out data acquisition and control functions including controlling access to the cable television network by the terminals The remote data processors communicate with the terminal units utilizing both time and frequency division multiplexing in a frequency shift key mode Communication between the remote data processor and the home terminals is preferably on the coaxial cable utilized for transmitting commercial programming for the television network The central data processor includes a minicomputer interfacing with input/output devices and external data links Each remote data processor includes a microcomputer having input/output devices attached thereto and interfacing between the minicomputer and the remote terminal units

Performance of a class of parallel spread-spectrum code acquisition schemes in the presence of data modulation

Abstract: An acquisition procedure for data-modulated direct-sequence spread-spectrum systems is investigated. The correlation time is partitioned into subintervals, and the integration results in these subintervals are noncoherently combined for detection. The tradeoff between noncoherent combining loss and data modulation degradation guides the optimum choice of the number of subintervals. Two forms of data modulation are considered, namely, the alternate-data and random-data cases. The parallel acquisition schemes discussed allow multiple code-phase offsets to be examined at each test. The circular state diagram approach is used to analyze the performances of these schemes. The theory presented is valid for a class of such parallel schemes. >

The NPL ultrasound beam calibrator

Abstract: The calibrator consists of a multielement membrane hydrophone made from polyvinylidene fluoride which is mounted in a versatile test-tank and linked to a fast data acquisition and presentation system. Acoustic output parameters of both simple medical ultrasonic systems and complex automatic scanners operating in imaging modes can be determined in a straightforward manner. Designed as a comprehensive measurement system, with the calibration traceable to United Kingdom national standards and the software configured to conform with written standards, it provides a convenient and rapid method of determining the acoustic output for both manufacturers and users of medical ultrasonic equipment. A detailed description of all aspects of the beam calibrator is given. The computer operating system is described, followed by an analysis of the postprocessing calculations which are applied to the acquired waveform data for the determination of acoustical parameters. Finally, a full assessment of the sources of uncertainty in the measurements is given, together with a comparison of results obtained using a reference measurement system. >

High Speed Rangefinder

Abstract: We present a new type of high speed range finder system that is based on the principle of triangulation range-finding. One of the unique elements of this system is a novel custom range sensor. This sensor consists of a 2D array of discrete photo-detectors. Each photo-detector is attached to an individual memory element. A slit-ray is used to illuminate the object which is then imaged by the sensor. The slit-ray is scanned at a constant angular velocity, so elapsed time is a direct function of the direction of the slit source. This elapsed time is latched into each individual memory element when the corresponding detector is triggered. The system can acquire the basic data required for range computation without repeatedly scanning the sensor many times. The slit-ray scans the entire object once at high speed. The resulting reflected energy strip sweeps across the sensor triggering the photo-detectors in succession. The expected time to acquire the data is approximately 1 millisecond for a 100x100 pixel range data. The sensor is scanned only once at the end of data acquisition for transferring the stored data to a host processing computer. The range information for each pixel is obtained from the location of the pixel and the value of time (direction of the slit source) stored in the attached memory element. We have implemented this system in an abbreviated manner to verify the method. The implementation uses a 47 x 47 array of photo-transistors. Because of the practical difficulty of hooking up the entire array to individual memories and the magnitude of the hardware involved, the implementation uses only 47 memories corresponding to a row at a time. The sensor is energized a row at a time and the laser scanned. This yields one row of data at a time as we described before. In order to obtain the whole image, we repeat this procedure as many times as we have rows, i.e, 47 times. This is not due to any inherent limitation of the method, but due to implementational difficulties in the experimental system. This can be rectified when the sensor is emitted to custom VLSI hardware. The time to completely obtain a frame of data (47 x47) is approximately 80 milliseconds. The depth measurment error is less than 1.0%.

Data acquisition and processing equipment for testing automotive vehicles

Abstract: Data acquisition and processing equipment permits simultaneous testing of a plurality of automotive vehicles located at different test stations of a technical test center. The equipment comprises remote control boxes each having an electronic identity, a display console enabling operators to assign each control box to one vehicle, a CRT screen for displaying test data as well as a menu of test operations, remote control receivers for the signal transmitted by the control boxes, a computerized central unit connected to the display console, to the different test stations, to the display screen and to the remote control receivers.

Fast single-element PN acquisition for the TDRSS MA system

Abstract: The authors present a description and performance analysis of a new PN code acquisition approach for the tracking and data relay satellite system with multiple access (TDRSS MA) return subsystem. The MA subsystem uses a phased array on-board the TDRS with 30 elements whose received signals are each independently retransmitted to the ground for beam forming. In the current operational system, acquisition is performed by using a serial search of the possible PN epochs on the beam-formed 30-element signal. In contrast, the new approach performs acquisition on a single (arbitrary) element signal using a parallel (i.e., simultaneous) search of all possible PN epochs. Since only one element signal is used, no beam forming is required prior to PN acquisition. The approach is based on sampling and digital processing of the received signal. The new method also incorporates techniques which counteract the effects of Doppler and asynchronous data modulation. The probability of correct acquisition as a function of acquisition time, signal-to-noise ratio, data rate, and user satellite Doppler is analyzed. >

Adaptive enhancement of x-ray images

Abstract: The quality of x-ray images is significantly enhanced by adjusting the x-ray system operating parameters in real time during acquisition of x-ray data to take information about the part into account adaptively. X-ray energy, x-ray flux, and integration time can all by varied independently and in combination to improve the signal to noise ratio in the image. The x-ray data from a previous subsection of the image is processed to determine optimum system operating parameters for a next image subsection. x-ray tube voltage is adjusted to change x-ray energy and keep αL close to 2 over all image subsections. X-ray tube current is adjusted to change x-ray flux and data acquisition integration time is adjusted to keep the signal to noise ratio within limits.

A digital hardware correlation system for fast ultrasonic data acquisition in peak power limited applications

Abstract: The theoretical and experimental evaluation of a digital hardware correlation system for low-power ultrasonic applications is presented. The system, which incorporates dual Golay code matched filtering, is capable of 20-MHz processing rates with a signal-to-noise-ratio enhancement (SNRE) of 23 dB over a conventional pulse-echo system operating at the same peak power levels. The effects of digitization have been investigated, and a TTL (transistor transistor logic)-based hardware correlator has been developed. For many applications, low-voltage driving followed by differential detection is sufficient, permitting the system to be used in a number of power-limited environments. Sample tests conducted on three different transducers have demonstrated that the system is operational over a wide variety of probe configurations. >

Analysis and assessment of errors in a parallel data acquisition system for electrical impedance tomography.

Abstract: Three possible data collection configurations for electrical impedance tomography are considered. These are serial current but parallel voltage measurement or full parallel operations. Measurement errors due to stray capacitances, common mode signals and contact impedance are considered. It is concluded that a parallel system offers advantages in terms of either speed or signal to noise ratio by may give larger common mode errors.

A digitally-controlled, real-time, analog power-system simulator for closed-loop protective relaying testing

Abstract: A power-system simulator is described that uses a control computer to configure an electronic analog model of a three-phase symmetrical power system and to set the model parameters. The model closely represents the dynamics of the real world up to 3 kHz. Precision high-power amplifiers convert the low-level analog signals to supply the protective relays under test. The design has been influenced by the key feature of closed-loop operation, with the relays functioning dynamically and in real time with the model. Nonlinearities are represented where significant, including the fault, transformer, arrester, and series-capacitor protection modules. The long-line transmission models represent the traveling-wave phenomena. Numerous system configurations can be selected. The data-acquisition system utilizes four digital computers, storing analog data at up to 25 kHz rate. The computers also analyze and manipulate the analog and event data and control a color plotter and printer. The emphasis of the discussion is on the analog models and the power amplifier designs. >

Application of LabVIEW in higher education laboratories

Abstract: The LabVIEW software system, which builds instrumentation applications on the Apple Macintosh, is described. Application programs are called virtual instruments (VIs). A VI consists of a front panel and a block diagram. The front panel has ready-to-go controls such as graphs, knobs, and switches. The users selects, moves, and sizes these controls to define a user interface. Behind the front panel is the block diagram, which is the actual executable program. In the block diagrams, icons and other graphical elements are wired together using the graphical programming language 'G' LabVIEW has an inherent hierarchy in that icons representing other VIs are used as functions. Thus LabVIEW has just one building block, the VI, which can be a program or a function. LabVIEW includes ready-to-go VIs for acquisition and analysis. Acquisition VIs support GPIB (general-purpose interface bus), RS-232 and plug-in boards for analog to digital, digital to analog, digital input/output, and timing. Over 100 instrument driver VIs are available for GPIB and RS-232 instruments. Analysis VIs include statistics, digital signal processing, filters, and numerical methods. Users can also write their own VIs. Applications of LabVIEW in engineering laboratories are mentioned. >

Optimization of MR protocols: a statistical decision analysis approach.

Abstract: A new method of optimizing MRI data acquisition protocols is presented Tissues are modeled with probability density functions (PDFs) of tissue parameter values (such as T1, T2) The imaging data acquisition process is modeled as a mapping from a tissue parameter space to a signal strength space Tissue parameter PDFs are mapped to signal strength PDFs for each tissue in a clinical problem The efficacy of an MRI protocol is evaluated using the methods of statistical decision analysis applied to the signal strength PDFs, including the propagation of noise This procedure evaluates the ability to discriminate different tissues based on the signal strengths produced with the protocol The model can incorporate an arbitrary number of tissues, parameters, and pulse sequences in the protocol The multivariate nature of MRI and the observed broad distribution of tissue parameter values makes this model more appropriate for optimizing data acquisition protocols than methods which maximize the signal-difference-to-noise ratio between discrete values of the tissue parameters It is shown that these two methods may calculate different optimal protocols The method can be used to optimize data acquisition for quantitative computer-based tissue classification, as well as imaging Data acquisition and image processing philosophies are discussed in light of the method

Design and performance of a 215 GHz pulsed radar system

Abstract: A high-power 215-GHz pulsed radar system developed for remote-sensing applications is described that is capable of making backscatter measurements from terrain targets at ranges of several kilometers under normal atmospheric conditions. By using separate transmit and receive antennas, the amplitudes of the polarization matrix elements may be measured conveniently. A dedicated data acquisition system was developed allowing up to 15 range gates to be sampled at 100-ns intervals. Instrument stability of +or-1.0 dB yields accurate scattering measurements of a variety of terrestrial targets. System performance and calibration, together with measurements of snow backscatter coefficients made during early 1987, are discussed. >

Multiple transmission path seismic telemetering system

Abstract: In a marine seismic data acquisition system, a plurality of seismic data transmission paths are utilized to conduct seismic data to a central recording unit from seismic data acquisition modules positioned along the length of cable. Signals from a plurality of data acquisition modules are applied to each of the transmission paths. Data acquisition modules which apply seismic signals to a given transmission path may be spaced and substantially uniform distances along the length of the cable and may be interspersed with data acquisition modules which apply seismic data to each of the other transmission paths. The operation of the data acquisition modules is synchronized by means of a signal transmitted continually from a central recording unit. Each section of the cable includes a plurality of remote units distributed along the cable section for detecting seismic signal. Each section includes a data acquisition module which receives command signals from a central recording unit and which receives seismic data signals from the remote units and transmits seismic data signals to the central recording unit.

Measurement of instantaneous losses in switching power devices

Abstract: A novel technique is proposed for measuring instantaneous power and energy losses in static switching devices during the different operating intervals (turn-on delay, rise time, on-state, turn-off delay, full time, and off-state) of a switching cycle. To this end, a system for measuring voltages and currents is used, based on sampling at 200 Ms/s for data acquisition. The data are then transferred to a personal computer (PC), where they are conditioned and processed to obtain the instantaneous values and the average values of power losses for any desired duty cycle or single impulse. It is concluded that the high-speed digital acquisitions of voltage and current data along with the possibility of automatically processing on a PC allows the calculation of the losses during the fast switching transients with a greater degree of accuracy and detail than that afforded by classical techniques. >

Adaptive Sensitivity / Intelligent Scan Imaging Sensor Chips

Abstract: CMOS VLSI imaging sensors are described, which employ a novel approach to image acquisition and processing. Principles of biological visual systems, such as adaptation and selective attention, are applied to achieve a high performance imaging system. The Adaptive Sensitivity mechanism enables the acquisition of extremely wide dynamic range, much wider than that of conventional semicon­ ductor sensors, while preserving image details and while dynamically adapting to the image contents. The Intelligent Scan mechanism filters in only the areas of interest, thus reducing the amount of transmitted visual data in an intelligent, image-dependent, adaptive manner, The sensor are complemented with an image processing system, described in a companion paper. 1. INTRODUCTION The principles of organization of biological vision systems provide a most valuable inspiration to the design and construction of intelligent technological vision systems. Consider the fundamental task of image acquisition with high resolution over wide field-of-view. Man-made visual systems, even while employing the most powerful available supercomputers or parallel processors, cannot acquire and manipulate on-line the bit rate of 109 bit per second necessary under the circumstances [1, 2, 3], Yet, biological systems with very limited resources, comprising slow components operating on a time scale of milliseconds, can process this enormous bit rate, and are more than capable of multidimensional pro­ cessing in this environment.We seek to gain some insight into these mechanisms, in order to better design efficient visual data acquisition and processing systems. In this paper we focus on two relatively well understood mechan­ isms of collection and selection of visual data, namely Adaptive Sensitivity combining nonlinear pro­ cessing and multilevel feedback loops, and selective acquisition and processing implementing a non- uniform scheme of computational resources allocation, and outline the design of a family of VLSI based sensors which exploit these biological principles of organization [4, 5, 6, 7],

A computer based data acquisition system for teaching transients and switching phenomena and performing research on digital protection

Abstract: The authors present a computer-based model for demonstrating and teaching fault-induced transients, switching phenomena, and power with particular reference to teaching and advancing the concepts of digital protection of power systems. The design and implementation of a digitally controlled switching circuit is described. A data-acquisition system for sampling the current and voltage waveforms used in conjunction with a special interface with a VAX 11/750 or a personal computer to analyze the data is presented. An example of qualitative study for inrush current and fault-induced transients in a power transformer is shown. A mathematical model for the inrush current in a power transformer that accounts for time-varying and random parameters and that offers a basis for developing methods for digital protection of power transformers is presented. Finally, the integration of the model in teaching senior and graduate-level subjects related to power-system transients and protection is summarized. >

Area detectors for X-ray spectroscopy

Abstract: Area detectors greatly increase the efficiency of data acquisition in spectroscopic applications. The operating principles, advantages and limitations of two types of detectors system are described. They are the microchannel plate (MCP) with resistive anode readout, and the silicon charged-coupled-device (CCD), both with and without MCP enhancement. The linearity, size, resolution, quantum efficiency, noise specifications, stability, and uniformity of response are discussed. Data acquisition electronics are described briefly. The use of the devices is illustrated with applications to electron and soft X-ray spectroscopy.

A programmable medical data acquisition system chip

Abstract: A medical data acquisition system chip has been integrated using a BiMOS (bipolar metal-oxide semiconductor) process. This chip integrates a low-noise bipolar instrumentation amplifier, a programmable switched-capacitor notch filter, an 11-bit ADC (analog-to-digital converter), a 7-bit DAC, and an asynchronous serial interface. Biomedical signals such as ECG (electrocardiogram), EEG (electroencephalogram), invasive blood pressure, temperature, respiration, and cardiac output are picked up by transducers, probes, and electrodes. Typical signal levels are 50 mu Vp-p for the EEG and 1 mV p-p for the ECG. These low level biological signals are converted into voltages or currents. >