National Instruments Data Acquisition Card Research Articles

BH hysteresis measurement system for thin soft magnetic materials

In this work, a computer controlled automated system is designed for the evaluation of magnetic properties of thin soft magnetic materials. Magnetic measurements were conducted using a National Instrument Data Acquisition card, a signal generator, a power amplifier circuit for the signal voltage, and an AD620 voltage amplifier circuit for the induced voltage in the secondary coil. The LabVIEW software was used for controlling the hardware and processing the experimental data points to draft a BH-hysteresis loop for the sample. A dedicated feedback loop algorithm was designed for controlling the waveform of the flux density at the secondary coil during the magnetization process. Based on the results obtained, it is shown that the accuracy of coercivity measurement is increased using the sinusoidal flux density. The high accuracy instrumentation amplifier circuit together with the flux density control feedback loop made it possible to examine the magnetic properties of thin samples.

Dynamic Clamp on a Windows PC.

Dynamic clamp is a powerful tool for interfacing computational models and real cells. We describe here how to set up and carry out dynamic clamp experiments using a patch clamp amplifier, a National Instruments data acquisition card, and the freely available QuB software that operates on a PC running MS Windows.

Ocular Artifact Suppression in Multichannel EEG Using Dynamic Segmentation and Enhanced wICA

ABSTRACTThe artifacts such as ocular, muscle and certain electrical disturbances contaminate the Electroencephalogram (EEG). Wavelet enhanced independent component analysis (wICA) with static segmentation preserves little information of both spectral and coherent characteristics of neural activity. However, the considerable amount of valuable information can be preserved with novel automatic dynamic size segmentation of multichannel EEG signal with wICA. Most of the signal information lost in the threshold process (inappropriate threshold value) and this could be overcome with an adaptive threshold approach. It is assumed that the brain neural activity is a Gaussian random distribution with zero mean only for initial state.The 16 channel EEG signals are acquired with Ocular Artifact (OA). The subject is instructed to blink an eye during the time of recording. A National Instrument (NI) data acquisition card is used to acquire the EEG data in MATLAB with sampling rate of 1024 Hz. Statistical parameters like Standard deviation, mean power (PSD), root mean square error (RMSE) are used for analysis and comparison. The proposed dynamic segmentation method is better for suppression of ocular artifacts which preserves the brain neural activity as compared with static segmentation. The artifacts related with eye blinking are removed completely and successfully preserve spectral and coherent characteristics of EEG activity of interest. It is proved that automatic dynamic segmentation is a key tool. The presented method is best suitable for suppression of OA and estimation of brain neural activity.

Femtosecond Stimulated Raman microscopy: home-built realization and a case study of biological imaging

The progresses of femtosecond laser physics have had a significant impact on research and development of nonlinear microscopy techniques, such as Stimulated Raman scattering microscopy. The main advantages of this technique, based on vibrational spectroscopy, is its abilities to perform label-free imaging with high sensitivity, high spatial and spectral resolution, 3D sectioning capability and fast time of image acquisition (typically a few seconds). The main aim of this paper is to demonstrates the home-built realization of an imaging system based on Stimulated Raman Scattering (SRS) powered by femtosecond laser sources, using a National Instrument data acquisition (NI-DAQ) card. The SRS microscope is obtained by the integration of an SRS experimental set-up with a commercial laser scanning microscope. The successful implementation of the imaging system is demonstrated reporting label free images of polystyrene beads with diameter of 3 microns and evaluating their signal to noise ratio. Finally, the reliability of our system in a biological environment is tested. Taking advantage of SRS microscopy, subcellular localizations of lipid droplets inside adipocyte cells are demonstrated.

Ultrafast pump-probe signal detection using a data acquisition card

This work demonstrates the homebuilt, cost effective, pump probe signal detection using an advanced version of National Instrument data acquisition (NI-DAQ) card, which is used for multiple purposes in the same experiment. This advanced DAQ card is used as a controller for the linear stage, as an oscilloscope, and also for simultaneous acquisition of the signal from two photodiodes in synchronization with linear stage. The fast sampling rate of the DAQ card is used to quantify the peak power of the femtosecond laser pulse. This enables easier, faster, pulse to pulse data acquisition. A balanced detection technique is employed here, where the output from the two photodiodes are simultaneously sampled by the single DAQ card and is used to minimize pulse to pulse and slowly varying long-term fluctuations which are inherent to the laser source. We also review the significant developments in the DAQ card technology which helps to bypass the need for sophisticated instruments like lock-in amplifier or boxcar integrator, digital delay generator. This method is quite general and can be used in any experiment, where one needs to quantify the intensity variations in an experiment.

A novel measuring module for spindle rotational accuracy based on virtual instrument

The spindle rotational accuracy is an important indicator to evaluate the characteristic of a machine tool. In this article, an easy-to-use measuring module is proposed based on virtual instrument platform. A new method for measuring rotational speed and angular orientation using an adaptive filtering method to processing the target installation eccentricity is proposed, instead of using the encoder. This method can reduce the measuring cost and make the measurement more convenient, without affecting the measuring accuracy. Meanwhile, the selective principle of target installation eccentricity for rotating sensitive direction is investigated by theoretical analysis and numerical simulation. Based on the proposed method, measuring module is developed. National Instruments data acquisition card and capacitive sensors are used to acquire the displacement signals of the spindle rotational error motion. Contrast experiments with the commercial measuring software are performed to validate the feasibility and repeatability of the proposed measuring module. The experimental results demonstrate that the developed measuring module can reach the same precision using less test parameters.

Electric Measurement of the Critical Current, AC Loss, and Current Distribution of a Prototype HTS Cable

HTS cable is an emerging technology for electricity power transmission. It is very important to set up an accurate and easy-to-build measurement system to characterize HTS cables. In this paper, a novel measurement system has been developed to measure the ac losses for a prototype HTS cable using cancelation coil technique. This system is based on the National Instrument Data Acquisition card. It can also be used to measure the critical current and current distribution in the prototype cable. The prototype cable has been innovatively designed using an improved particle swarm optimization algorithm which is more computationally efficient than conventional methods. The measurement system will be improved further by introducing an elaborate pre-amplifier prior to data collection process and the result will be compared with theoretical calculations for validation.

Plataforma virtual para el mando local y remoto de un brazo robótico de apoyo para la educación en ingeniería

En este artículo se presenta el diseño e implementación de una plataforma virtual, que permite la simulación y mando local y remoto del brazo robot tipo SCARA llamado UV-CERMA, presente en el Laboratorio de Robótica de la Escuela de Ingeniería Eléctrica y Electrónica de la Facultad de Ingeniería de la Universidad del Valle, el robot UV-CERMA ha estado subutilizado desde hace algunos años debido a lo obsoleto de su sistema de control. La plataforma, enfocada con los lineamientos de educación en ingeniería está compuesta por dos aplicaciones que permiten la simulación y el mando y control locales y remotos para el robot, una de las aplicaciones se programó haciendo uso del paquete de National Instruments LabVIEW y la otra aplicación se realizó por medio de software libre, por medio del lenguaje de código abierto Java, ambos desarrollos implementan los modelos cinemático directo y cinemático inverso, un módulo para la planificación y ejecución de trayectorias, otro módulo para el monitoreo de variables y un modelo 3D del robot. Para la manipulación del robot se tiene una interfaz con un joystick, que lo hace más versátil. Las aplicaciones se comunican al robot real mediante una tarjeta de adquisición de datos de National Instruments NI USB-6211, y para el mando remoto la plataforma cuenta con una arquitectura cliente/servidor usando sockets TCP/IP.

Vectorized data acquisition and fast triple-correlation integrals for Fluorescence Triple Correlation Spectroscopy

Fluorescence Correlation Spectroscopy (FCS) is widely used to quantify reaction rates and concentrations of molecules in vitro and in vivo. We recently reported Fluorescence Triple Correlation Spectroscopy (F3CS), which correlates three signals together instead of two. F3CS can analyze the stoichiometries of complex mixtures and detect irreversible processes by identifying time-reversal asymmetries. Here we report the computational developments that were required for the realization of F3CS and present the results as the Triple Correlation Toolbox suite of programs. Triple Correlation Toolbox is a complete data analysis pipeline capable of acquiring, correlating and fitting large data sets. Each segment of the pipeline handles error estimates for accurate error-weighted global fitting. Data acquisition was accelerated with a combination of off-the-shelf counter-timer chips and vectorized operations on 128-bit registers. This allows desktop computers with inexpensive data acquisition cards to acquire hours of multiple-channel data with sub-microsecond time resolution. Off-line correlation integrals were implemented as a two delay time multiple-tau scheme that scales efficiently with multiple processors and provides an unprecedented view of linked dynamics. Global fitting routines are provided to fit FCS and F3CS data to models containing up to ten species. Triple Correlation Toolbox is a complete package that enables F3CS to be performed on existing microscopes. Program summaryProgram title: Triple Correlation Toolbox (suite)Catalogue identifier: AEOP_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEOP_v1_0.htmlProgram obtainable from: CPC Program Library, Queen’s University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 50189No. of bytes in distributed program, including test data, etc.: 6135283Distribution format: tar.gzProgramming language: C/Assembly.Computer: Any with GCC and library support.Operating system: Linux and OS X (data acq. for Linux only due to library availability), not tested on Windows.RAM: ≥512 MB.Classification: 16.4.External routines: NIDAQmx (National Instruments), Gnu Scientific Library, GTK+, PLplot (optional)Nature of problem:Fluorescence Triple Correlation Spectroscopy required three things: data acquisition at faster speeds than were possible without expensive custom hardware, triple-correlation routines that could process 1/2 TB data sets rapidly, and fitting routines capable of handling several to a hundred fit parameters and 14,000 + data points, each with error estimates.Solution method:A novel data acquisition concept mixed signal processing with off-the-shelf hardware and data-parallel processing using 128-bit registers found in desktop CPUs. Correlation algorithms used fractal data structures and multithreading to reduce data analysis times. Global fitting was implemented with robust minimization routines and provides feedback that allows the user to critically inspect initial guesses and fits.Restrictions:Data acquisition only requires a National Instruments data acquisition card (it was tested on Linux using card PCIe-6251) and a simple home-built circuit.Unusual features:Hand-coded ×86-64 assembly for data acquisition loops (platform-independent C code also provided).Additional comments:A complete collection of tools to perform Fluorescence Triple Correlation Spectroscopy—from data acquisition to two-tau correlation of large data sets, to model fitting.Running time:1–5 h of data analysis per hour of data collected. Varies depending on data-acquisition length, time resolution, data density and number of cores used for correlation integrals.

Effective Speed Control in 3-Phase BLDC Motor by Reaching Law based Sliding Mode Technique

In this paper a Sliding mode controller (SMC) scheme based on the power rate reaching law approach has been proposed for the inner loop current control of the 3-Phase Brushless DC motor (BLDC) drive. A proportionalintegral (PI) controller is used to control the outer loop speed performance. The developed PI-SMC control scheme is simulated on MATLAB/SIMULINK platform under a sequence of load torque disturbances incremented up to 100% to demonstrate efficient speed tracking. Experimental verification of the developed scheme is carried out under no load conditions using National Instruments Data Acquisition Card (NI DAQ) card 6229 as the interface with MATLAB environment. The experimental results validate the performance of the developed scheme. General Terms Sliding Mode Control

Laser photothermal radiometric instrument for industrial steel hardness inspection

To meet the industrial demand for on-line steel hardness inspection and quality control, a non-contact, non-destructive laser photothermal radiometric instrument (HD-PTR) was developed. The instrument is equipped with a non-liquid-nitrogen-cooled HgCdZnTe (MCZT) detector, a National Instruments data acquisition card with a Dynamic System Analysis (DSA) module, and control software. A series of industrial steel samples which included automotive screws and aircraft gears (flat or curvilinear) were examined. The effective hardness case depths of these samples ranged from 0.21 mm to 1.78 mm. The results demonstrated that three measurement parameters (metrics) can be extracted when using a fast swept-sine photothermal method. These parameters include the phase minimum (or peak) frequency, fmin, the half width, W, and the area, S. It was found that they are complementary for evaluating widely different ranges of hardness case depths. fminis most suitable for large case depths, and W and S for shallower case depths.

Development of Soft Sensor to Identify Flow Regimes in Horizontal Pipe Using Digital Signal Processing Technique

The work described in this article is a new analytical and experimental study of two-phase gas−liquid horizontal flow in a conduit for flow pattern identification by a digital signal processing technique. The data are acquired online using a pressure transducer and a National Instruments data acquisition card. The true signal voltage changes rather smoothly as a function of the number of samples, whereas many kinds of noise are added; as a result, rapid, random changes in amplitude from point to point within the signal are observed. To reduce the noise, a smoothing technique is employed. In the smoothing, the data points of a signal are modified so that the individual points that are higher than the immediately adjacent points are reduced and points that are lower than the adjacent points are increased. This naturally leads to a smoother signal. For this purpose, the simplest smoothing algorithm, namely, a simple moving average, is employed and is able to successfully eliminate the noise. After eliminating the noise, the slope of the curve is continuously tracked to determine sudden or abrupt changes. It is interesting to note that, from the signal obtained, the slope is always decreasing in nature and the magnitude is on the order of 5 × 10−3. According to the data and the slope, different flow regimes can be identified by using cross-correlation method.

Nonlinear finite element simulation for magnetic flux leakage tester

The paper reports about the building up a computer controlled measurement system based on National Instruments Data Acquisition card and National Instruments LabVIEW software package. The aim of this research is to detect manufactured surface cracks on steels by applying a magnetic flux leakage testing method. First of all, a finite element method based on the procedure to analyze the behavior has been implemented of the measurement system under construction. One important question is the position of the sensors or of the detecting coils. The finite element procedure contains a two dimensional arrangement. First, eddy currents have been neglected, but the nonlinear characteristic of the specimen has been taken into account by a single valued function. In this paper, the developed measurement system, which is partially ready to work, and the nonlinear finite element procedures are presented as well.

PIC microcontroller-based RF wireless ECG monitoring system

This paper presents a radio-telemetry system that provides the possibility of ECG signal transmission from a patient detection circuit via an RF data link. A PC then receives the signal through the National Instrument data acquisition card (NIDAQ). The PC is equipped with software allowing the received ECG signals to be saved, analysed, and sent by email to another part of the world. The proposed telemetry system consists of a patient unit and a PC unit. The amplified and filtered ECG signal is sampled 360 times per second, and the A/D conversion is performed by a PIC16f877 microcontroller. The major contribution of the final proposed system is that it detects, processes and sends patients ECG data over a wireless RF link to a maximum distance of 200 m. Transmitted ECG data with different numbers of samples were received, decoded by means of another PIC microcontroller, and displayed using MATLAB program. The designed software is presented in a graphical user interface utility.

Comparison of STFT and wavelet transform methods in determining epileptic seizure activity in EEG signals for real-time application

Electroencephalography (EEG) is widely used in clinical settings to investigate neuropathology. Since EEG signals contain a wealth of information about brain functions, there are many approaches to analyzing EEG signals with spectral techniques. In this study, the short-time Fourier transform (STFT) and wavelet transform (WT) were applied to EEG signals obtained from a normal child and from a child having an epileptic seizure. For this purpose, we developed a program using Labview software. Labview is an application development environment that uses a graphical language G, usable with an online applicable National Instruments data acquisition card. In order to obtain clinically interpretable results, frequency band activities of δ, θ, α and β signals were mapped onto frequency–time axes using the STFT, and 3D WT representations were obtained using the continuous wavelet transform (CWT). Both results were compared, and it was determined that the STFT was more applicable for real-time processing of EEG signals, due to its short process time. However, the CWT still had good resolution and performance high enough for use in clinical and research settings.