Digital Integrator Research Articles

Novel digital integrator and differentiator

A novel digital integrator and a novel digital differentiator are presented. Both the integrator and the differentiator are of first order and thus eminently suitable for real-time applications. Both have an almost linear phase. The integrator is obtained by interpolationg two popular digital integration techniques, the rectangular and the trapezoidal rules. The resulting integrator outperforms both the rectangular and the trapezoidal integrators in range and accuracy. The new differentiator is obtained by taking the inverse of the transfer function of the integrator. The effective range of the differentiator is about 0.8 of the Nyquist frequency.

The simulation errors introduced by the SPICE transient analysis

The SPICE transient simulations of simple circuits that can be easily solved by hand often give erroneous results. The numerical errors are investigated and analyzed using the analogy of the simulation program with a digital integrator. The transfer function of the digital integrator is defined through the z-transform. The solving method implemented in SPICE is one of the possible approximations of the z-transform. This approximation has some good properties but also some drawbacks; it warps the frequency and it is not step invariant.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A digital integrator and scan generator coupled with dynamic scanning for scanning tunneling microscopy

A novel digital integrator circuit has been engineered for constant-current mode STM feedback control. In contrast to analog integrators that rely on charging or discharging of a capacitor in an amplifier feedback loop, the integrator uses a 16-bit digital counter that is rapidly incremented or decremented depending on whether the tunneling current is higher or lower than a reference value. The counter drives a digital-to-analog converter (DAC) whose output is amplified and used to control the STM Z-axis scanner. A computer’s parallel input port records the DAC output word at each sampling point, directly giving the digital value of the tip position. The integrator is used in conjunction with a two-axis 16-bit scan generator. The Z-axis feedback reference circuit is used to dynamically control the STM’s lateral scanning rate, and scan rates of 300 μm s−1 are demonstrated. The digital integrator and scan generator facilitate fast switching between different modes of STM operation, allowing glitch- and drift-free locking of tip position, interchange of axes, scanning or switching the sign of the tip bias, and flexible tailoring of the feedback response.

Role of Weather Radar in Disaster Management

Severe mesoscale atmospheric phenomena like cyclones and severe thunderstoms associated with high winds and heavy rainfall cause great destruction of property and life. These phenomena occur frequently over our country. It is, therefore imperative that these hazardous atmospheric systems are detected in time for issuing early warning to the user agencies.During last four decades, since evolution of radar, the technique has emerged as a potential tool for detection and forecasting of severe weather systems. High power S, C, and X-band radars, combined with various types of displays viz, PPI, RHI, and REI, are very useful for qualitative studies of weather systems. The evolution of Digital Video Integrator Processor (DVIP) gives the quantitative measurement of rainfall and total rainfall which helps early prediction of flash floods. Doppler radar systems combined with other peripherals is an effective tool for quantitative measurement for turbulence and high wind regimes. India has an adequate network of st...

A direct digital control for the phase-controlled rectifier

Direct digital control of the phase-controlled rectifier (PCR) is implemented with a minimum control hardware structure. A digital phase-locked voltage control (PLVC) without detecting the line voltage is presented. An inner fast control loop is proposed to stabilize the PCR system and to obtain its constant loop gain. In the inner loop, an averaging function is introduced to feed back the average DC voltage of the PCR output without the feedback filter. Its synchronism is modeled and analyzed. An optimal constant digital integral, proportional, and measurable variable feedback (IPM) current controller with a time-multiplied performance index is also proposed to obtain a good dynamic response of the output current. All control functions are implemented with an Intel 8797 single-chip microcomputer. Experimental results show that the scheme gives good dynamic and static performance for the PCR system.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The design of a precision digital integrator for use in an active vibration control system

Active feedback control techniques may be used to modify the dynamic response of a vibrating structure. This paper describes the design and implementation of a digital integrator which is used in a control system to modify the structural frequency response of a cantilever beam. The beam, which is driven by band-limited stationary excitation, may be modeled as a second order system with the modal series truncated and approximated by a residual stiffness term. The design of a high precision digital integrator is found to be necessary. Two integrator designs are implemented, and the integrator used for experimental work is designed to compensate for the half-sample delay introduced by the sample-hold circuitry; this design provides integration which is accurate to within 1° over a frequency range of 1·5 Hz to the Nyquist frequency. The controller is used to provide velocity and displacement signals from an input acceleration signal which allows alteration of the modal parameters of the first mode of the beam. The controller is implemented using a Texas Instruments TMS 32020 Digital Signal Processor operating at sample rates of up to 44 kHz, and experimental results are presented which demonstrate the alteration of the natural frequency and damping ratio of the fundamental mode of the cantilever.

Magnetism

Metrolab, known worldwide for its precision NMR teslameters, has now introduced the Model PDI 5025 precision digital integrator.

Spectral analysis, digital integration, and measurement of low backscatter in coherent laser radar

The operation of a surface acoustic wave spectrum analyser and digital integrator is reviewed. Expressions are derived for signal to noise ratio in the measured voltage spectrum with an approximation for the general case and rigorous treatment for the low signal case. A previous calibration study is re-evaluated to provide a final calibration for the atmospheric backscatter data accumulated by the airborne LATAS (laser true airspeed) coherent laser radar system.

Chromatographic Data Systems: A Critical Review

Abstract A. Perspective and Goal This review article spans over 30 years of chromatography advancement and development. Coincident with the evolution of chromatography was that of laboratory data automation. The first commercial gas chromatograph appeared in 1955,1 whereas the first commercial digital integrator appeared in 1961.2 Several data systems emerged in the late 1960s3–6 that led to the arrival of the first commercial computer-based electronic integrator in 1972.7 Two major advancements were most influential to the development of data automation; initially there was the development of solid-state operational amplifiers that led to analog peak integrators. Prior to this time, manual peak integration methods were used. Then the advancement of integrated circuits allowed digital logic to be introduced. Today, all commercial and noncommercial laboratory integrators are sophisticated computer-based systems. This article generally follows this chronological development.

Use of a scanning densitometer or an ELISA plate reader for measurement of nanogram amounts of protein in crude extracts from biological tissues

Protein contents of crude extracts from plant and animal tissues can be rapidly assayed using a Coomassie blue dye-binding procedure combined with scanning densitometry. Total protein is extracted from 100 mg of fresh-frozen or dried-ground tissue using 1 ml of extraction buffer. One-microliter aliquots of standard solutions or crude extracts are spotted in rows on a suitably sized sheet of Whatman 3MM chromatography paper. The dried samples are stained with Coomassie brilliant blue R-250 (0.2%, w v , in acidified 50% MeOH) for 20 min and rinsed twice with acidified 20% MeOH. After drying, protein concentrations are read as reflectance using a scanning densitometer and peak heights or peak areas recorded using a digital integrator. In an alternative procedure, each spot is cut from the sample sheet and the dye-protein complex eluted in 1% sodium dodecyl sulfate (SDS) using an ultrasonic cleaner. Absorbance is subsequently read in a microwell sample holder at 590 nm with an enzyme-linked immunosorbent assay plate reader. Both procedures offer distinct advantages over previously reported methods. They are significantly faster when large numbers of samples are processed, they avoid interference by chlorophyll, dithiothreitol, SDS, 2-mercaptoethanol, Nonidet P-40, and phenylmethylsulfonyl fluoride (and other protease inhibitors) and they yield marked improvements in sensitivity, providing measurements of protein concentration below 100 and 200 ng·μl −1, respectively.

Automatic gas chromatographic evaluation of the performance of membranes used for permeation processes

The separation of liquid mixtures by permeation through membranes frm a liquid stream to a gas phase is influenced by the permeability and the selectivity of the polymeric layer. These propeties depend on various parameters: time, temperature, swelling of the membrane in water and in organic solvents, compositiion of the permeating mixture, etc. The evaluation of a given membrane is accomplished by measuring the distribution of the compounds to be separated over the liquid and the gas phase. This procedure is time-consuming because many analyses of both phases must be performed in order to investigate the effect of the various parameters. Full automation of the analysis and of the evaluation of the results has been achieved by connecting an external events module to a digital integrator in order to connect an automatic gas-sampling valve and a small-volume liquid-sample valve to the carrier gas source and to the permeating streams, respectively. Each valve is automatically filled with samples coming from the liquid or gas circuit and activated to deliver the sample to the gas chromatographic unit, through a low-dead-volume injector, suitable for on-column introduction of both liquid and gaseous samples. The gas chromatographic columns were packed with various amounts of porous polymer-bead stationary phases (Porapak or Chromosorb “Century Series”) in order to separate water efficiently fromthe organic components of the permeating mixture (alcohols, glycols). A thermal conductivity detector was used. Computer programs were developed for automatic evaluation of the quantitative results, recording of the data, calculation of the retention-index values, plotting of the time—composition graphs, and calculation of the membrane selectivity as a function of time, temperature and composition of the permeating mixture. Low-cost personal computers are suitable for this applicatioin. With minor modifications and by using other columns and detectors, the system can be used for automatic analysis of any combination of liquid or gas streams.

Design, Construction and Characterization of a Low-Cost High-Precision Digital Integrator

ABSTRACT A low cost, high precision electronic integrator allowing accurate integration of analog input signals over a wide dynamic signal range for long and short integration periods is described. The utility of this integrator is demonstrated in the controlled potential reduction of Pb++ where the i - t curve is represented by the number of coulombs accumulated and displayed in digital form. With this value and application of Faraday's Law, the n value of the electrode reaction is calculated. The obtained n value of 1.95 shows good agreement with the expected value of 2.00.

Data acquisition and instrument control system for ion flight time measurements in mass spectrometry

A microcomputer system is described that provides instrument control and data acquisition for ion flight time measurements in mass spectrometry. This system is designed specifically for time-resolved ion momentum spectrometry (TRIMS), a new mass spectrometry/mass spectrometry (MS/MS) technique that utilizes time-of-flight measurements in a magnetic sector instrument. The flexibility of the design, however, makes it applicable to many types of instruments that employ ion flight time measurements. The heart of the system is a digital boxcar integrator with 10-ns timing precision. The microcomputer has control of both the magnetic field and the sampled flight time. Software, written in forth, allows all standard MS/MS scans to be obtained, even those requiring complex linked scans of the magnetic field strength and the sampled flight time. Data that demonstrate the accuracy of these scans are shown for metastable decompositions of n decane.

The power spectrum of digital FM as produced by digital circuits

A simple exact method is given for calculating the power spectrum of a frequency modulated filtered M-ary data signal. The power spectrum and its discrete components are given in closed form for any pulse shape. The pulses are those generated by a digital transversal filter and the FM modulator is that composed of an ideal digital integrator followed by a phase modulator (look-up table).

A Wafer-Scale Digital Integrator Using Restructurable VSLI

Wafer-scale integration has been demonstrated by fabricating a digital integrator on a monolithic 20-cm/sup 2/ silicon chip, the first laser-restructured digital logic system. Large-area integration is accomplished by laser programming of metal interconnect for defect avoidance. This paper describes the technology for laser welding and cutting, the design methodology and CAD tools developed for wafer-scale integration, and the integrator itself.

A wafer-scale digital integrator using restructurable VSLI

Wafer-scale integration has been demonstrated by fabricating a digital integrator on a monolithic 20-cm2silicon chip, the first laser-restructured digital logic system. Large-area integration is accomplished by laser programming of metal interconnect for defect avoidance. This paper describes the technology for laser welding and cutting, the design methodology and CAD tools developed for wafer-scale integration, and the integrator itself.

Vapor-liquid equilibria for the ternary system 2-propanol-chloroform-benzene at 50.degree.C

Vapor-liquid equilibrium (VLE) measurements were made for the 2-propanol-chloroform and 2-propanol-chloroform-benzene systems at 50/sup 0/C. VLE data for the two constituent binaries at 50 /sup 0/C have been reported: 2-propanol-benzene (1); chloroform-benzene (2). The apparatus for experimental work is a Boublik vapor-recirculating still described by Ohta et al. (3). All first-grade chemicals supplied were purified for VLE measurements. 2-Propanol was distilled in a 1-m glass column packed with McMahon packing after being dried over anhydrous copper sulfate. Chloroform was washed with concentrated sulfuric acid, dilute sodium hydroxide, and distilled water. It was dried over calcined sodium carbonate and fractionally distilled in an atmosphere of nitrogen. Benzene was recrystallized 3 times. Vapor and liquid sample compositions were analyzed by a Shimadzu (GC-7A) gas chromatograph combined with a Shimadzu (ITG-2A) digital integrator. Measured variables have the following errors: composition, 0.002 mole fraction; pressure, 13.3 Pa; temperature, 0.05 K.

A multisensor pyranometer for determination of the direct component and angular distribution of solar radiation

This paper describes a technique for determining the direct component and the angular distribution of the diffuse component of solar radiation. The information is obtained by measurement of the total radiation on slopes of different orientations. This has been done using a new multidirectional pyranometer, called a multipyranometer, specially developed for this purpose. The instrument incorporates 25 radiation sensors mounted on a metal hemisphere. Each sensor consists of a blackened copper plate with a semiconductor temperature transducer. Sensors are enclosed in an evacuated glass envelope and each of them is connected to its own digital integrator. Computer programs have been developed for data quality control, monitoring and computations. Some of the results from laboratory tests and solar radiation measurement obtained over a period of two years are given. Comparisons are made between observations obtained with the multipyranometer and those obtained with conventional pyranometers. Experimental observations are also compared with some radiation models.

Accessing and Using Digitized Radar with Microcomputers

ABSTRACT RADAR provides a means of monitoring precipitation over large areas in real-time. National Weather Service network radars have digital video integrator processors that convert radar echoes into digital information based upon echo strength. Commercial microcomputers were configured and programmed to receive this digital radar information. Rainfall rates determined from the radar data were used to estimate soil moisture changes and rainfall runoff hydrographs. Successful implementation of equipment and algorithms demonstrate that recent advances in microcomputer technology allow application of radar data in real-time.

An electronic device for accurate quantification of neuronal mass activity based on a digital integration method

Quantification of different kinds of neuronal mass activity was performed using an integrative method. For this purpose an electronic device was designed and constructed which is based on a fully digital approach. High precision of the method and an easy way to interface with a digital computer are the advantages of this strategy when compared to other techniques. Performance of quantification and the possibility of the universal use of the device are demonstrated by two examples. (1) Quantitative analysis of whole nerve bundle activity is demonstrated in the case of phrenic nerve mass activity. (2) The usefulness of the digital integrator is further verified in quantification of theta waves of the human EEG as a rather different field of application. In addition, the device is valuable as a tool for the analysis of EMGs. The described digital integrator has many advantages compared to conventional analog integrators, such as autorange feature, very high dynamic range, excellent long-term stability, in principle unlimited integration times and interface capability to a digital computer; it avoids all problems associated with the application of high-impedance integrator operational amplifiers.