General Purpose Interface Bus Research Articles

UHF-Band Radar Cross Section Measurements With Single-Antenna Reflection Coefficient Results

This article discusses the challenges and advantages of measuring radar cross section (RCS) using reflection coefficient measurements from a single-antenna test setup. In practice, arranging two ultrahigh-frequency (UHF) antennas in a quasi-monostatic configuration is difficult due to their large physical size. In addition, the coupling power between the two antennas can be much larger than the signal of interest, imposing further limitations on this configuration. However, traditional RF measurement hardware and postprocessing algorithms are combined to extract RCS across frequency and azimuthal angle accurately with the $S_{11}$ values collected from a single antenna. This is made possible by using vector background subtraction and time-gating windowing techniques to suppress multipath reflections, clutter, and mismatch reflection while increasing the measurement’s dynamic range. The test setup utilizes the National Instruments LabVIEW software for control and automation, a General Purpose Interface Bus (GPIB)-enabled vector network analyzer, and a rotary table allowing for experiments to be conducted in an anechoic chamber or an outdoor measurement range. Experiments are conducted at the University of Oklahoma in the far-field anechoic chamber and outdoors using the components mentioned above to validate the derived algorithms and measurement concepts. The chamber setup is calibrated using a metal sphere to extract the RCS of a smaller metal sphere. The initial RCS extraction had an average error of 4.9 dBsm over the 300–1000-MHz frequency range using only calibration and vector background subtraction. After applying time gating, the error is further reduced to 0.54 dBsm. The implemented test setup is accomplished using traditional measurement equipment and a single antenna allowing for a portable, flexible, and low-cost solution for RCS measurements in the UHF band.

PortaDrop: A portable digital microfluidic platform providing versatile opportunities for Lab-On-A-Chip applications.

Electrowetting-on-dielectric is a decent technique to manipulate discrete volumes of liquid in form of droplets. In the last decade, electrowetting-on-dielectric systems, also called digital microfluidic systems, became more frequently used for a variety of applications because of their high flexibility and reconfigurability. Thus, one design can be adapted to different assays by only reprogramming. However, this flexibility can only be useful if the entire system is portable and easy to use. This paper presents the development of a portable, stand-alone digital microfluidic system based on a Linux-based operating system running on a Raspberry Pi, which is unique. We present “PortaDrop” exhibiting the following key features: (1) an “all-in-one box” approach, (2) a user-friendly, self-explaining graphical user interface and easy handling, (3) the ability of integrated electrochemical measurements, (4) the ease to implement additional lab equipment via Universal Serial Bus and the General Purpose Interface Bus as well as (5) a standardized experiment documentation. We propose that PortaDrop can be used to carry out experiments in different applications, where small sample volumes in the nanoliter to picoliter range need to be handled an analyzed automatically. As a first application, we present a protocol, where a droplet is consequently exchanged by droplets of another medium using passive dispensing. The exchange is monitored by electrical impedance spectroscopy. It is the first time, the media exchange caused by passive dispensing is characterized by electrochemical impedance spectroscopy. Summarizing, PortaDrop allows easy combination of fluid handling by means of electrowetting and additional sensing.

The data acquisition and control system for the operation of ASDEX pressure gauge for the measurement of neutral pressure in ADITYA Tokamak

Bayard-Alpert (BA) type hot cathode ionisation gauge is widely used to measure neutral pressure precisely in vacuum system below 10−3 Torr pressure. Neutral pressure measurement in magnetic confinement fusion experiments is quite challenging for standard BA type gauge due to higher pressure limitation and its ionisation is affected by strong magnetic and electrical fields. To overcome the above limitations, a special hot cathode ionisation gauge, named ASDEX Pressure Gauge (APG) system was developed by G. Haas at the Max-Planck-Institute, Germany. The APG system can work in high magnetic field up to 6 T and high temperature plasma environment with broad pressure measurement range from 10−1 to 10−6 mbar with fast response (<10 msec) and good noise immunity.In the present work, we report the design and development of control and data acquisition of ASDEX Pressure Gauge (APG) for ADITYA Tokamak to measure real time neutral pressure during the high temperature plasma. The developed system can achieve synchronous control of gauge controller using General Purpose Interface Bus (GPIB) and data acquisition of ion emission current of gauge head using Peripheral Component Interconnect (PCI) based data acquisition module. Initially, the APG calibration with standard BA type hot cathode ionization gauge had been carried out using the test set-up of low magnetic field and ultrahigh vacuum system with gases like H2, Ar, He. For APG calibration for various pressure ranges of these gases, precise gas feed control system has been developed using controller based hardware and LabVIEW based software. After testing and calibration, the APG was installed on ADITYA tokamak and calibrated under high magnetic field of ADITYA. The developed APG control system is configurable for presenting the gauge parameters before the plasma discharge. During plasma discharge, the analog signal equivalent to neutral pressure is acquired in real-time using simultaneous sampling analog to digital converter (ADC) module. The acquired raw data and processed real time pressure can provide valuable neutral pressure/density information of Tokamak plasma.

Automated Test System for Test and Evaluation of C-Band Transmitter Packages for Geosat Spacecrafts

The aim of this paper is to develop an Automated Test System (ATS) for the Test and Evaluation of C-Band Transmitter packages for GEOSAT Space crafts using Virtual Instrumentation. Efficiency, coverage, quality and accuracy for the test and evaluation of Device Under Test (DUT) can be increased by Automated Testing. Minimizing the errors anticipated with manual intervention. Automated Test System using Virtual instrumentation (VI) combines rapid development software and modular, flexible hardware to create user-defined test systems. Here Modular PXI (Peripheral component interface Extensions for Instrumentation) instruments from National Instruments are used with NI-LabVIEW software for realizing the ATS. For characterizing the C-Band Transmitter, Spectrum analyzer &amp; Digital Multimeter (DMM) is configured in PXI form-factor and the Power supply is controlled through GPIB (General Purpose Interface Bus) bus. The complete software is developed using NI LabVIEW which takes care of configuring the test condition and analyzing the DUT performance. The user friendly GUI well takes care of user interaction to the ATS.

Evaluating tool wear by measuring the real-time contact resistance

A method is proposed to diagnose wear and to determine the replacement schedule for a working end-mill cutter. Changes in the contact area between a working end-mill cutter and the workpiece during a milling process lead to a real-time variation in the contact resistance. Measuring the real-time contact resistance using a micro-ohm meter and a GPIB (general-purpose interface bus) interface control card allows the wear in a working end-mill cutter to be determined. Real-time contact resistance values for a working end-mill cutter are measured and recorded every second. The experimental results demonstrate that when the milling cutter operates continuously for about 20,000 s, the contact resistance decreases to about 25% of the original value for the brand new state. This method can be used for the future design of milling machines. If the value of the contact resistance for a working end-mill of the same type approaches this value, the cutter should be replaced in order to maintain efficient machining.

GPIB based instrumentation and control system for ADITYA Thomson Scattering Diagnostic

The ADITYA Thomson Scattering Diagnostic is a single point Ruby laser based system with a spectrometer for spectral dispersion and photomultiplier tubes for the detection of scattered light. The system uses CAMAC (Computer Automated Measurement And Control) based control and data acquisition system, which synchronizes the Ruby laser, detectors and the digitizer. Previously used serial based CAMAC controller is upgraded to GPIB (General Purpose Interface Bus) based CAMAC controller for configuration and data transfer. The communication protocols for different instruments are converted to a single GPIB based for better interface. The entire control and data acquisition program is developed on LabVIEW platform for versatile operation of diagnostics with improved user friendly GUI (Graphical User Interfaces) and allows user to remotely update the laser firing time with respect to the plasma shot. The software is in handshake with the Tokamak main control program through network to minimize manual interventions for the operation of the diagnostics. The upgraded system improved the performance of the diagnostics in comparison to earlier in terms of better data transmission rate, easy to maintain and program is upgradable.

Design and Implementation of USB Driver and Firmware based on Usbtmc Protocol

Background/Objectives: USB is most common and fast protocol that is replacing all other wired communication protocol. Main aim of this project is to replace the GPIB pin of instruments with USB. Methods/Statistical analysis: Generally all the instruments use General purpose interface bus i.e. GPIB pin for transfer of data. But it is very bulky and also it is not fast. This project replaces the bulky GPIB pin with faster and smarter USB. We are using USBTMC protocol to design the driver as well as firmware. USBTMC is the test and measurement protocol which is based on USB 2.0 specifications. Findings: Here, Beagle bone black board is used as the device where we can write the firmware. Driver program is written and registered in Linux PC. The Output is shown in minicom. The data is transferred from PC to the device through USB cable using USBTMC protocol. This is verified by getting the output as the USBTMC device. Applications/Improvements: This protocol is very new. It can be used in various applications such as instruments used in medical, industries, security system, and home appliances.

Two-dimensional magnetic field dependence of zero and finite voltage steps in current–voltage characteristics of superconducting quantum interference devices

Modulation characteristics of Josephson current through superconducting quantum interference devices (SQUIDs) by two dimensional scanning of external magnetic field have been studied. Vertical type SQUIDs composed of two niobium/aluminum-oxide/niobium (Nb/Al-oxide/Nb) tunnel junctions are fabricated using magnetron sputtering system. In order to measure the magnetic dependence of the critical current Ic through SQUIDs, Hx and Hy magnetic field components parallel to junction edges are scanned in two dimensions (2-D) by using two pairs of Helmholtz coils driven in GPIB (General Purpose Interface Bus) system. The 2-D magnetic field (Hx, Hy) dependences of the Josephson current Ic and the resonant current steps Istep at finite voltage in the current–voltage curves of SQUIDs have been obtained. Modulation characteristics of SQUIDs with different junction separation are measured. The resonant current steps Istep are also studied using superconducting planar circuit model.

GPIB Communication Design of Programmable Instrument

GPIB (General Purpose Interface Bus) is the international instrument interface standard. From the perspective of programmable instrument implementing GPIB communication, the paper describes the mode of NAT9914 implementing GPIB communication in details. America National Instrument Company is the leader of GPIB technique. The paper uses GPIB communication card and communication software NI488.2 of NI Corporation to verify the designed GPIB communication interface. In the program, GPIB communication interface is applied to the communication of programmable power supply of computer. The paper makes systematic introduction on standard command for programmable instrument and applies SCPI to control program-controlled power supply.

Two-dimensional magnetic field dependence of zero and finite voltage steps in current–voltage characteristics of rectangular shape niobium tunnel junctions

► Josephson current I c through Nb superconducting junction was measured. ► I c dependence on H x , H y magnetic fields was product of Fraunhofer pattern. ► Numerical simulation of I c −( H x , H y ) matched the measured result. ► Modulation period inversely proportional to the vertical edge length of junction. ► Resonant current steps studied by superconducting planar circuit model. Modulation characteristics of Josephson current through rectangular shape niobium/aluminum-oxide/niobium superconducting junctions have been studied by two-dimensional (2-D) scanning of the external magnetic field. In order to obtain the magnetic field dependence automatically, two pairs of Helmholtz coils are driven by two current sources with GPIB (General Purpose Interface Bus) system. The 2-D magnetic field dependences of the Josephson current and the resonant current steps of the current–voltage characteristics of the Nb/Al-oxide/Nb tunnel junction have been measured. The I c −( H x − H y ) characteristics are the product of two Fraunhofer diffraction patterns in H x and H y directions parallel to each junction edge, and are also numerically calculated by assuming that distribution of phase difference γ and the junction current density I 0 inside the rectangular shape junction area have been modulated in perpendicular direction to the external magnetic field. This modulation period is inversely proportional to the junction length perpendicular to the external magnetic field. The resonant current steps are also considered using superconducting planar circuit model. The distributions of the magnetic flux, the electrode current and the junction current have been studied.

Two-dimensional magnetic field dependence of Josephson current and resonant current steps at finite voltage of square shape superconducting tunnel junctions

In this article, modulation characteristics of Josephson current through square shape niobium/aluminum-oxide/niobium superconducting junction by two-dimensional scanning of external magnetic field have been studied. Two pairs of Helmholtz coils are controlled by two current sources with general purpose interface bus system to obtain the magnetic field dependence automatically. The distribution of Josephson current density inside the square junction area is obtained. The 2-D magnetic field dependences of the resonant current steps of the current-voltage characteristics of the Nb/Al-oxide/Nb tunnel junction have also been measured using the junction voltage as the parameter.

Focus on lasers and imaging

Focus on lasers and imaging

Supercapacitor Testing for Power Smoothing in a Variable Speed Offshore Wave Energy Converter

This paper investigates power smoothing in a full-scale offshore oscillating water column (OWC) wave energy converter (WEC) by integrating supercapacitors (SCs) with the inertia of a Wells turbine controlled at variable speed. With the simulation package Simulink developed by MathWorks, a model is developed for the WEC system utilizing sea-state data and an SC system is sized to smooth and reduce the grid peak power for a 570-kW (peak) system. Long component lifetime is a requirement for offshore WECs. Hence, a computer-controlled test rig has been built to validate SC lifetimes to manufacturer's specifications and determine application lifetime. Cycle testing is carried out on individual SCs at room temperature and also at rated temperature utilizing a thermal chamber and equipment interconnected by the general purpose interface bus (GPIB) and programmed by the MathWorks developed computing environment Matlab. Application testing is carried out using time-compressed scaled-power profiles from the model to allow a comparison of lifetime degradation. The SCs under standard testing at ambient and rated temperature, and application testing at ambient temperature, have undergone approximately 4 000 000, 700 000, and 500 000 cycles, respectively. The results demonstrate cycle lifetimes in excess of manufacturer specifications.

Active Instrument Controller With Script Interpreter

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> A concept of an active instrument controller with a script interpreter is proposed. It represents a gateway between the computer network and the instrument bus, but, in addition, it can locally execute the measurement script. This introduces distributed code execution in the measurement system, where time-critical measurement loops are locally executed with the main program running on a personal computer (PC). The local execution capability also allows stand-alone operation. We demonstrate the concept with a self-developed active General Purpose Interface Bus (GPIB) controller that uses a CompactFlash (CF) slot. By inserting a communication or a storage card, the controller can operate in network or storage mode. Performance comparison of different operational modes shows a clear advantage of local script execution over conventional network use. Its execution speed is comparable to the commercial script performance implemented in some Keithley's instruments but, in contrast, is applicable to a wide range of different measurement instruments and setups. </para>

Observation on Probability Function by Measuring Time Series of Electric Property in Gadolinium Nitrate Crystal at Low Temperature

The observation of the dynamics of fluctuation in a nonlinear nonequilibrium material system in a low-temperature region gives valuable information for developments in the physics of both nonlinear quantum dynamics and nonequilibrium thermodynamics. Rare-earth nitrate crystals have the same crystal habit and triclinic space group. The crystal structure is independent of temperature above 80K. Nonlinear and nonequilibrium phenomena have been observed in rare-earth nitrate crystals. Distinct intermittent nonperiodic oscillations (bursts) were observed in the measurement of the time series data for conductivity. The phenomena could be classified into a macroscopic chaos in a dissipative dynamical system. The effect of rare-earth elements on the fluctuation was found in the electric properties of the crystals. The characteristic properties of rare-earth nitrate crystals were observed in the electric measurement of the crystals in the lower-temperature region below 200K. We have measured the time series of ac conductivity, and clarified unknown properties of rare-earth nitrate crystals in the low-temperature region below 200K. A singularity in the probability distribution function was observed by measuring the time series of ac conductivity in the direction perpendicular to the c-axis of the gadolinium nitrate crystal at 11K. The result was given in the present note. A single crystal was grown in a gadolinium nitrate aqueous solution by evaporation at temperatures from 312 to 309K for 1994 h. The sample was 0:040 0:005 cm in thickness and 0:276 0:005 cm in area. The time series data of ac conductivity at 2 kHz were measured using a twophase digital lock-in amplifier (EG&G Princeton Applied Research 5210) and an analog memory recorder (Yokogawa AR1100). The experimental apparatus was controlled by a computer with a general-purpose interface bus (GPIB). The time series data of ac conductivity perpendicular to the c-axis (c2-axis) were measured at a sensitivity within 10 11 1 cm . The measurement was performed under isothermal condition controlled within 0:1K using a closed-cycle refrigerator system (Janis Research CCS-300). At 11K, with a sampling time of 50ms, 5000 data points were collected for the time series data. Figure 1 shows the time series of the fluctuation 0 for the real part 0 of the complex conductivity at 2 kHz for the electric field E applied in the direction perpendicular to the c-axis at 11K in a cooling cycle. The fluctuation 0 is defined by the relation 0 1⁄4 0 0, where 0 is the average derived from the data of the conductivity 0, given by 0 2:0298 10 6 1 cm 1 at 11K. Bursts occur randomly as nonperiodic unstable oscillations in the time series of 0 at the temperature. The probability distribution function of the time series data { 0} on the semilogarithm scale is given in Fig. 2. The probability function could not be classified into both standard Gaussian and Lorentzian line shapes. The functional form of the probability function is symmetrical and has a sharp peak as seen from Fig. 2. Figure 3 shows a log– log plot of the probability distribution function versus the fluctuation 0. The result indicates that the singularity of the probability function is proportional to ð 0Þ , where the exponent s of the power law is given by s 1⁄4 1:43 0:2. The temperature variation in the probability functions was observed in other rare-earth nitrate crystals, which were classified into the Gaussian one. 0 50 100 150 200 250 -10 -5 0 5 10

Self-Calibrating Automated Characterization System for Depressed Cladding EDFA Applications Using LabVIEW Software With GPIB

A self-calibrating automated characterization system for depressed cladding applications is demonstrated utilizing the laboratory virtual instrument engineering workbench (LabVIEW) software and general purpose interface bus (GPIB) interface. The automation system consists of a tunable laser source (TLS), optical spectrum analyzer (OSA), attenuator, laser diode controller, and a personal computer, and all these instruments are networked using GPIB cables. Compared to manual measurement techniques, the overall experiment time is reduced by 80% while the data acquisition increases in accuracy, with a lower uncertainty value of plusmn 0.012 dB after self-calibration. From the experiment, the use of the automated self-calibrating software has allowed for the characterization of the depressed cladding erbium-doped fiber (EDF).

MIMO Channel Sounder Based on Two Network Analyzers

Different channel sounders are reported in the literature to measure the multiple-input-multiple-output (MIMO) wireless channel, most of them being dedicated systems. In this paper, a MIMO channel sounder that is based on two network analyzers is presented. The measurement process is totally controlled by a PC via a wireless local area network (WLAN), a local area network (LAN), and a general-purpose interface bus, and they are synchronized by using two global positioning systems (GPSs). The system is restricted to static propagation environments. An advantage of this system is its configurability, thanks to which it is not wireless system dependent. Last, initial measurements in a laboratory of a university at 900 MHz for a 4times4 MIMO system are also presented.

Two-dimensional magnetic field dependence of current-voltage characteristics of rectangular, hexagonal and triangle shape superconducting junctions and DC-SQUIDs

Modulation characteristics of Josephson current through rectangular, hexagonal and triangle shape superconducting junctions and dc-SQUIDs by two-dimensional scanning of external magnetic field have been studied. Two pairs of Helmholtz coils were controlled by two current sources with GPIB (General Purpose Interface Bus) system to obtain the magnetic field dependence automatically. In the case of rectangular shape junction, the dependence of Josephson current on Hx-Hy plane has become the product of the two Fraunhofer patterns in the direction Hx, Hy parallel to each edge of this rectangular shape. The periods of these modulations were inversely proportional of each length of the rectangular shape perpendicular to the magnetic field. In the case of hexagonal shape junction, we have found hexagonal symmetry in the dependence of Josephson current on the Hx-Hy plane. Six ridges of the modulation surface were clearly observed in the directions of six edges of the hexagonal shape (0, 60, 120, 180, 240 300 degrees). In triangle shape junctions, six ridges of the modulation surface were also clearly observed in the directions of three edges of the triangle shape. In the case of dc-SQUIDs, the modulation pattern was the product of the sensitive modulation of the period of the magnetic flux quantization of the hole of the vertical dc-SQUID and the insensitive modulation pattern of each square junction itself.

Strategies for improved temporal and spectral resolution in in vivo oximetric imaging using time‐domain EPR

A radiofrequency (RF) time-domain electron paramagnetic resonance (EPR) instrument operating at 300, 600, and 750 MHz was used to image tumor hypoxia with high spatial and temporal resolution. A high-speed signal-averaging Peripheral Component Interconnect (PCI) board with flexibility in the input signal level and the number of digitized samples per free induction decay (FID) was incorporated into the receive arm of the spectrometer. This enabled effective and fast averaging of FIDs. Modification of the phase-encoding protocol, and replacement of the General Purpose Interface Bus (GPIB)-based handshake with a PCI-based D/A board for direct control of the gradient amplifier decreased the gradient settling and communication overhead times by nearly two orders of magnitude. Cyclically-ordered phase sequence (CYCLOPS) phase cycling was implemented to correct for pulse imperfections and cancel out unwanted constant signals. These upgrades considerably enhanced the performance of the imager in terms of image collection time, sensitivity, and temporal resolution. We demonstrated this by collecting a large number of 2D images successively and rapidly. The results show that it is feasible to achieve accurate, 2D pO(2) maps of tumor hypoxia with 1-mm(2) resolution and minimal artifacts using a set of multigradient images within an acceptable measuring time of about 3 s, and 3D maps can be obtained in less than 1 min.

Perl with Tk and C Applied to Product Verification

Automotive multimedia devices are verified against requirements by applying analog signals and Controller Area Network (CAN) commands to the devices and recording their responses. Perl, Tk, and C were used to write a test sequencer and an EEPROM configuration tool at Visteon. This software is used in the product verification process. A variety of programming methods, including late binding, object oriented and procedural modules, inter-process communication, and graphical user interfaces are used in the software. The usefulness of these methods is discussed. The measurement of speed sensitive volume using General Purpose Interface Bus based instruments and a CAN network interface is described.