High-speed Digital Data Acquisition Research Articles

A high speed digital data acquisition system for the Indian National Gamma Array at Tata Institute of Fundamental Research

A digital data acquisition system for the Compton suppressed clover detector array has been implemented at the TIFR-BARC accelerator facility for the high resolution gamma ray spectroscopy using the Pixie-16 Digital Gamma Finder modules by XIA LLC. This system has a provision for simultaneous digitization of 96 preamplifier signals of high purity germanium crystals. The energy and timing characteristics of the clover detectors have been investigated in detail. In-beam data has been collected both in singles and in the coincidence mode. The system has been tested with 64 channels with each of the 64 crystals having an event rate up to 5kHz and 2-fold clover coincidence rate up to 15kHz. The use of the digital data acquisition system has improved the high counting rate handling capabilities for the clover array. Conventional systems with analog shaping are being replaced by digital system that provides higher throughput, better energy resolution and better stability for the multi-detector Compton suppressed clover array.

A versatile, multipurpose, high-speed digital data acquisition and generation system `PULSAR'

This paper presents a methodology and practical implementation of a high-speed digital data acquisition (DAQ) and generation system. Due to the general approach, the usability of the system is not limited to a specific application. It is a universal tool to evaluate high data rate systems such as ΣΔ converters.

Feasibility and applications of cone beam x-ray imaging for containerized wastes : Roney, T.; Galbraith, S.; White, T.; Clack, R.; O'Reilly, M. Idaho National Engineering Lab., Idaho Falls (United States), DE96002776/GAR, 29 pp. (1995)

Large area scintillation screens coupled to video and scientific-grade CCD cameras allow high speed digital data acquisition for both single 2-D x-ray projections and tomographic data sets comprised of multiple 2-D projections. While the data cquisition may proceed more rapidly than data acquisition using a linear detector array, there are geometric distortions associated with the projection cone angle long processing times for 3-D tomographic data. This paper reviews issues associated with processing and interpretation of the data and approaches to resolving some of the problems for containerized waste inspection. Results obtained with the Idaho National Engineering Laboratory`s Digital Radiography and Computed Tomography scanner are presented.

Large-scale structure in the far field of byoyant jets

The flow structure and entrainment mechanisms in the far field of a round vertical buoyant jet have been studied experimentally by use of an optical technique based on laser-induced fluorescence (LIF). A large number of essentially instantaneous tracer concentration profiles were recorded for each experimental run by combining LIF with linear photodiode array imaging and high-speed digital data acquisition. Analysis of the resulting high-resolution flow images indicates that the far-field region is dominated by the periodic passage of structures spanning the entire radial flow extent. Ambient fluid is entrained by vortical motions and is transported to regions deep into the flow interior. Correlation analysis discloses that the passage frequency of the structures scales with the local mean velocity and flow width. Conditional averaging of the data indicates that the downstream frontal region of the structure is well mixed and at higher concentration level than the back and side regions where ambient fluid is intermittently present. This results in an axial concentration gradient within the structure, analogous to the ramp-like pattern previously observed in heated air jets. In comparison to the momentum-driven flow the ambient fluid presence in the flow interior is greatly increased when body forces are the driving mechanism. This appears to result from the influence of buoyancy forces in the production of turbulent vortices at the integral scale. An important feature of both the momentum-driven and buoyancy-driven flows investigated is the strongly intermittent character of the concentration field. This raises the issue of the appropriateness of gradient-diffusion theories for the description of such flows.

Use of a new high-speed digital data acquisition system in airborne ice-sounding

A high-speed digital data acquisition and signal averaging system for borehole, surface, and airborne radio-frequency geophysical measurements was designed and built by the US Geological Survey. The system permits signal averaging at rates high enough to achieve significant signal-to-noise- enhancement in profiling, even in airborne applications. The first field use of the system took place in Greenland in 1987 for recording data on a 150 by 150-km grid centered on the summit of the Greenland ice sheet. About 6000-line km were flown and recorded using the new system. The data can be used to site a proposed scientific corehole through the ice sheet.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Directional velocity analyzer for measuring electron distribution functions in plasmas

A directional velocity analyzer has been developed for measuring electron distribution functions in plasmas. It contains a collimating aperture which selects particles from a narrow cone in velocity space and a retarding potential analyzer. The distribution function f(v, θ, φ) is obtained from a large number of analyzer traces taken at different angles θ, φ. In addition, the small analyzer can be moved in space and the measurements are time resolved so as to obtain the complete phase space information f (v, r, t). The large data flow of this seven-variable function is processed with a high-speed digital data-acquisition system. The new electron velocity analyzer is applicable over a wide parameter range in electron energies and densities. Various cases of anisotropic distributions such as beams, shells, tails, and drifts have been successfully investigated.

High-speed digital data acquisition of sarcomere length from isolated skeletal and cardiac muscle cells.

A digital data acquisition system has been developed which obtains sarcomere length data from a contracting skeletal muscle fiber or cardiac myocyte. The design is such that it can be used on any computer system capable of data channel operation (direct memory access).

Stochastic frequency-domain tissue characterization: application to human spleens ‘in vivo’

Ultrasonic waveforms backscattered from normal and pathologic human spleens were recorded in vivo using a high-speed digital data acquisition system. A frequency-domain analysis was performed for 50 digitized waveforms from each spleen, in which auto-correlations of frequency spectra were employed to measure the mean spacing among adjacent tissue scatterers. Mean scatterer spacing for normal spleens averaged 1.10 ± 0.14 mm, whereas abnormal, diffusely enlarged spleens had mean scatterer spacings averaging 1.52 ± 0.14 mm. The results of these measurements are in accord with those expected from splenic histology. The techniques described may be valuable in ultrasonic diagnosis of the spleen and other organs.

Noise reduction in relaxation kinetic experiments

The use of high-speed digital data-acquisition devices makes it possible to obtain a large number of points (>4000) for a single experiment during a short time interval. A suitable numerical treatment capable of reducing the periodic and random noise in relaxation-curves and of providing relaxation times and amplitudes of high accuracy is presented.

A low-cost high-speed digital data acquisition and display system

A flexible and inexpensive data acquisition and display system based upon the KIM-1 microcomputer module is described. A simple signal-conditioning circuit and program are shown that will allow events to be counted at rates to 1,000/sec and stored in successive time bins. The program counts events from each of two event detectors and stores the count of each detector in an independent set of time bins. Up to 127 16-bit bins are available to each event detector and bin width can be varied from 1 msec to 1 min. A separate input can be used to time-lock data collection to a specific stimulus allowing poststimulus histograms or IRTs to be collected. The collected data can be sequentially displayed as a decimal number on a built-in LED display and stored for later analysis on an inexpensive audio cassette recorder.

A new lidar signal processor using digital techniques to provide real-time display

An accurate high speed digital data acquisition system which records lidar data on magnetic tape is discussed. It features real-time processing of the data by means of a low cost dedicated processor. The system features dual-channel recording capability, and has two built-in gain-switching amplifiers, allowing the system to accurately record the entire return signal having a dynamic range in excess of 80 dB. Dual differential inputs are used to provide excellent noise immunity.

High-order moments of Reynolds shear stress fluctuations in a turbulent boundary layer

The cumulant-discard approach is used to predict the third- and fourth-order moments and the probability density of turbulent Reynolds shear stress fluctuations uv, the streamwise and normal velocity fluctuations being represented by u and v respectively. Measurements of these quantities in a turbulent boundary layer are presented, with the required statistics of uv obtained by the use of a high-speed digital data-acquisition system. Including correlations between u and u up to the fourth order, the cumulant-discard predictions are in close agreement with the measurements in the inner region of the layer but only qualitatively follow the experimental results in the outer intermittent region. In this latter region, predictions for the third- and fourth-order moments of uv are also obtained by assuming that the properties of both turbulent and irrotational fluctuations are Gaussian and by using some of the available conditional averages of u, v and uv.

Digital Data Recording of Boiler Response Testing

Since the installation of its first digitally controlled economic dispatch system in 1959, the Philadelphia Electric Company has been studying in increasing detail the dynamic characteristics of its generating units, for these characteristics affect the performance of the overall system. In planning for a new digital control and data transmission complex, a study was included in the overall project aimed at restructuring the controls of existing units in order to improve their characteristics. A first step in this study was the development and purchase of a new high speed digital data acquisition system for use in the testing and analysis of power plant equipment.

High-Speed (Subsecond) Measurement of Heat Capacity, Electrical Resistivity, and Thermal Radiation Properties of Molybdenum in the Range 1900 to 2800 K.

A technique is described for the high-speed measurement of heat capacity, electrical resistivity, hemispherical total and normal spectral emittances of electrical conductors at high temperatures (above 1900 K) with millisecond resolution. Duration of an individual experiment, in which the specimen is heated from room temperature to close to its melting point, is less than one second. Temperature measurements are made with a high-speed photoelectric pyrometer. Quantities are recorded by a high-speed digital data acquisition system which has a resolution of approximately one part in 8000. Time resolution of the entire system is 0.4 ms. Results on the above properties of molybdenum in the temperature range 1900 to 2800 K are reported and are compared with those in the literature. Estimated inaccuracy of measured properties in the above temperature range is: 2 to 3 percent for heat capacity, 0.5 percent for electrical resistivity, 3 percent for hemispherical total emittance and 2 percent for normal spectral emittance.