Computer-controlled Power Supply Research Articles

Pyroelectric response of single-crystal samples of trigycine sulphate in three dimensions

This study presents an investigation of the pyroelectric properties of single-crystal samples of triglycine sulphate (TGS) in 3D. The use of cubic samples and a suitable measurement setup made it possible to investigate the pyroelectric properties of TGS samples along the polar b axis and the mutually perpendicular directions to this axis. The measuring station was self-designed and constructed using a Keithley nanovoltmeter, a Rhode & Schwarz computer-controlled power supply, a GW INSTEK multimeter, a measuring chamber with Peltier cells, and a LabView custom user interface. Measurements of the pyroelectric response in 3D allowed us to conclude that the hydrogen bond between glycines G2-G3 may be strongly engaged in the phase transition in TGS, and is probably the trigger for the process. Our 3D investigation of the phase transition mechanism in single-crystal TGS is very promising in terms of research into the best pyroelectric materials for infrared thermal sensors.

Realization of a Laboratory Tuneable Colour Light Source

A spectrally tuneable colour light source (TCLS) has been designed and constructed at Physikalisch-Technische Bundesanstalt (PTB), Germany. It consists of an integrating sphere with 24 LEDs which are driven by a computer-controlled power supply. It is intended for producing any visible spectral distribution and to mimic various light sources for use in laboratories as a calibration source. With the help of an integrated spectrometer, a closed loop operation was introduced to improve the performance of the TCLS and to spectrally stabilize its output spectrum. Before practical realization of the TCLS a series of simulations have been made to predict its performance and capability with a number of different target spectrums. During the practical implementation we have encountered difficulties, namely optimization of the output spectrum, dependency of LED spectra on the electric current through the LED and temperature of the LED, non-linearity of LED’s luminous flux with respect to electric current through the LED and some difficulties with small synthesis coefficient values, which were all successfully solved.

Low-Cost Computer-Controlled Power Supplies for Optimization and Control of Electron Spectrometers

SynopsisNew Arduino-based power supply designs are presented that have direct applicability to electron spectrometers such as the (e,2e) spectrometer that is used in Manchester. Voltages from these supplies can be manually selected using digital potentiometers, or can be remotely controlled using LabVIEW. These new control routines allow the apparatus to explore both ground state and laser-excited targets.

Effective Power Signal Filtering Using LC Filters with Air Core Coils

Computer controlled power supplies are usually expensive when high performance (power, wide voltage range, low ripple factor and low response time) are required. This paper presents a simple and effective computer controlled DC system based on a commercial V/f inverter combined with a three-phase bridge rectifier and a LC power filter. Because of the widely variable frequency range of the V/f inverter when a wide range of voltage is required, amorphous or ferromagnetic core coils are avoided, and air core coils become an excellent solution to implement the filter and increase the efficiency of the power system. The proposed method for designing the LC filter is based on the full dynamic model of the filter-load set and the selection of the desired poles of the system according to the load to be coupled. The proposed topology lets obtain good time responses (setting time less than 100 ms) and good ripple factor (less than 1%) without any overshooting, even when low voltage output is required.

Spectrophotometric high-precision seawater pH determination for use in underway measuring systems

Abstract. Autonomous sensors are required for a comprehensive documentation of the changes in the marine carbon system and thus to differentiate between its natural variability and anthropogenic impacts. Spectrophotometric determination of pH – a key variable of the seawater carbon system – is particularly suited to achieve precise and drift-free measurements. However, available spectrophotometric instruments are not suitable for integration into automated measurement systems (e.g. FerryBox) since they do not meet the major requirements of reliability, stability, robustness and moderate cost. Here we report on the development and testing of a~new indicator-based pH sensor that meets all of these requirements. This sensor can withstand the rough conditions during long-term deployments on ships of opportunity and is applicable to the open ocean as well as to coastal waters with a complex matrix and highly variable conditions. The sensor uses a high resolution CCD spectrometer as detector connected via optical fibers to a custom-made cuvette designed to reduce the impact of air bubbles. The sample temperature can be precisely adjusted (25 °C ± 0.006 °C) using computer-controlled power supplies and Peltier elements thus avoiding the widely used water bath. The overall setup achieves a measurement frequency of 1 min−1 with a precision of ±0.0007 pH units, an average offset of +0.0005 pH units to a reference system, and an offset of +0.0081 pH units to a certified standard buffer. Application of this sensor allows monitoring of seawater pH in autonomous underway systems, providing a key variable for characterization and understanding of the marine carbon system.

Development of a bi-functional silica monolith for electro-osmotic pumping and DNA clean-up/extraction using gel-supported reagents in a microfluidic device

A silica monolith used to support both electro-osmotic pumping (EOP) and the extraction/elution of DNA coupled with gel-supported reagents is described. The benefits of the combined EOP extraction/elution system were illustrated by combining DNA extraction and gene amplification using the polymerase chain reaction (PCR) process. All the reagents necessary for both processes were supported within pre-loaded gels that allow the reagents to be stored at 4 degrees C for up to four weeks in the microfluidic device. When carrying out an analysis the crude sample only needed to be hydrodynamically introduced into the device which was connected to an external computer controlled power supply via platinum wire electrodes. DNA was extracted with 65% efficiency after loading lysed cells onto a silica monolith. Ethanol contained within an agarose gel matrix was then used to wash unwanted debris away from the sample by EOP (100 V cm(-1) for 5 min). The retained DNA was subsequently eluted from the monolith by water contained in a second agarose gel, again by EOP using an electric field of 100 V cm(-1) for 5 min, and transferred into the PCR reagent containing gel. The eluted DNA in solution was successfully amplified by PCR, confirming that the concept of a complete self-contained microfluidic device could be realised for DNA sample clean up and amplification, using a simple pumping and on-chip reagent storage methodology.

Multidimensional Damage Identification Based on Phase Space Warping: An Experimental Study

A multidimensional damage identification scheme developed in previous work is modified and investigated experi- mentally. An experimental apparatus consists of a driven two-well magneto-elastic oscillator, where a cantilever beam vibrates in a magnetic potential field perturbed by two electromagnets. These electromagnets are activated by a computer controlled power supply and their terminal voltages are considered a two-dimensional damage variable. The effect of total change in the supply voltage of the electromagnets is approximately 4% shift in the experimentally measured natural frequencies of small oscillations in each well of the potential. Experimental runs are started in a nominally chaotic regime. The battery voltages are altered on specific trajectories in the damage (voltage) phase space. Damage identification is accomplished based on the elastic vibration data collected using laser vibrometers and a accelerometer. The phase space warping based damage tracking feature vectors are estimated using a new phase space partitioning scheme. The damage identification is achieved by applying smooth orthogonal decomposition to the obtained statistics. The effect of the data record size on the quality of reconstructed damage trajectory is investigated in a series of experiments. It is also demonstrated that the new partitioning scheme considerably improves signal-to-noise ration of the identified damage states.

Tungsten coil atomic emission spectrometry

A tungsten coil atomic emission spectrometer is described and evaluated. The system employs a single tungsten coil as a combined atomizer and excitation source for the determination of metals by atomic emission spectrometry. The tungsten coil is extracted from a 150 W, 15 V commercial slide projector light bulb. A simple, laboratory constructed, computer-controlled power supply provides a constant current to the coil. A high-resolution Czerny–Turner monochromator with a charge coupled device detector completes the system. Simultaneous, multi-element analyses are possible within a 4 nm spectral window. Eleven test elements are used to characterize the system: Al (396.1 nm), Co (353.0 nm), Cr (427.1 nm), Dy (404.6 nm), Ga (403.3 nm), K (404.4 nm), Mn (403.1 nm), Pb (405.8 nm), Rb (420.2 nm), Sc (404.8 nm), and Yb (398.7 nm). Tungsten coil atomic emission detection limits are reported for these elements for the first time: 0.02 ng Al, 0.7 ng Co, 0.003 ng Cr, 0.01 ng Dy, 0.7 ng Ga, 0.3 ng K, 0.04 ng Mn, 10 ng Pb, 0.07 ng Rb, 1 ng Sc, and 0.003 ng Yb. The precision for the new technique is better than 13% relative standard deviation for all metals at concentrations two orders of magnitude above the detection limit. Aluminum, Cr, Mn, and K are determined in a standard reference material (trace elements in water) after simple dilution with water, and found values varied from certified values by up to 26%. The average tungsten coil lifetime was found to be 265 heating cycles. The elimination of the external radiation source needed for atomic absorption measurements results in an emission system that could be quite portable.

Developing the technique of measurements of magnetic field in the CMS steel yoke elements with flux-loops and Hall probes

Compact muon solenoid (CMS) is a general-purpose detector designed to run at the highest luminosity at the CERN large hadron collider (LHC). Its distinctive features include a 4 T superconducting solenoid with 6 m diameter by 12.5 m long free bore, enclosed inside a 10000-ton return yoke made of construction steel. Accurate characterization of the magnetic field everywhere in the CMS detector, including the large ferromagnetic parts of the yoke, is required. To measure the field in and around ferromagnetic parts, a set of flux-loops and Hall probe sensors will be installed on several of the steel pieces. Fast discharges of the solenoid during system commissioning tests will be used to induce voltages in the flux-loops that can be integrated to measure the flux in the steel at full excitation of the solenoid. The Hall sensors will give supplementary information on the axial magnetic field and permit estimation of the remanent field in the steel after the fast discharge. An experimental R&D program has been undertaken, using a test flux-loop, two Hall sensors, and sample disks made from the same construction steel used for the CMS magnet yoke. A sample disc, assembled with the test flux-loop and the Hall sensors, was inserted between the pole tips of a dipole electromagnet equipped with a computer-controlled power supply to measure the excitation of the steel from full saturation to zero field. The results of the measurements are presented and discussed.

A Hantzsch synthesis of 2-aminothiazoles performed in a heated microreactor system.

This paper presents the first example known to the authors of a heated organic reaction performed on a glass microreactor under electro-osmotic flow control. The experiments consisted of the preparation of a series of 2-aminothiazoles by means of a Hantzsch reaction of ring-substituted 2-bromoacetophenones and 1-substituted-2-thioureas carried out in microchannels, with the aim of investigating the generic utility of the reactor in carrying out analogue reactions. The reactions were performed on T-design microchips etched into a thin borosilicate glass plate and sealed over with a thick borosilicate top plate containing reservoirs. The mobility of the reagents and products was achieved using electro-osmotic flow (EOF), with the driving voltages being generated by a computer-controlled power supply. During the experiments the T-shaped chip was heated at 70 C using a Peltier heater, aligned with the channels and the heat generated by this device was applied to the lower plate. The degree of conversion was quantified by LC-MS using UV detection by comparison with standard calibration curves for starting materials and final products. In all cases, conversions were found to be similar or greater than those found for equivalent macro scale batch syntheses, thus illustrating the potential of this heated microreactor system to generate a series of compounds which contain biologically active molecules.

Correction of Aberrations of a Transmission Electron Microscope

One of the most striking problems in electron optics, the correction of resolution limiting aberrations by means of a corrector incorporated into the electron microscope column, has been solved during the last six years by demonstrating the improvement of resolution beyond the theoretical limit of the uncorrected Electron Microscope (EM). At first, in 1995 [1] with the correction of spherical and chromatic aberration of a dedicated Low Voltage Scanning Electron Microscope (LVSEM) and later, in 1997, with the correction of only spherical aberration of a commercially available 200 kV TEM [2]. The correction of spherical aberration of a dedicated Scanning Transmission Electron Microscope (STEM) at 100 keV primary energy has been demonstrated [3] and further improvements can be anticipated within the near future.These achievements could only be obtained due to the emergence of new computer technology and especially CCD-cameras in the case of TEM correctors. These two developments made it possible first to calculate the electron optical components more precisely and hence, to achieve a better understanding of the requirements on the hardware and second, to have a better computer control of the electron microscope and the corrector itself. The combination of these two new technologies made it possible to go towards an automatisation of the alignment. This simplification of the alignment of an even more complex system is achieved by means of a proper combination of image acquisition and dedicated software in order to analyze and measure the aberrations of an electron optical system on one side and on the other to have appropriate tools to compensate these aberrations by computer controlled power supplies [4,5].

Detector-stabilized FEL lamps as transfer standards in an international comparison of spectral irradiance

The spectral irradiance of lamp standards can be stabilized within a limited spectral range using a suitable selective detector to control the irradiance of the lamps. The capability of one commercial lamp facility incorporating a computer-controlled power supply was tested in an international comparison. A set of three lamps and the detector-stabilized power supply were circulated between the Physikalisch-Technische Bundesanstalt (PTB, Germany), the Helsinki University of Technology (HUT, Finland) and the Swedish National Testing and Research Institute (SP, Sweden) for the comparison, EUROMET project No. 475.

LLNL superconducting magnets test facility

The FENIX facility at Lawrence Livermore National Laboratory was upgraded and refurbished in 1996-1998 for testing CICC superconducting magnets. The FENIX facility was used for superconducting high current, short sample tests for fusion programs in the late 1980s-early 1990s. The new facility includes a 4-m diameter vacuum vessel, two refrigerators, a 40 kA, 42 V computer controlled power supply, a new switchyard with a dump resistor, a new helium distribution valve box, several sets of power leads, data acquisition system and other auxiliary systems, which provide a lot of flexibility in testing of a wide variety of superconducting magnets in a wide range of parameters. The detailed parameters and capabilities of this test facility and its systems are described in the paper.

Improved Slurry Sampling Electrothermal Vaporization System Using a Tungsten Coil for Inductively Coupled Plasma Atomic Emission Spectrometry

An improved ETV system for the determination of trace elements in diverse samples by slurry sampling ETV–ICP-AES is presented. It consists of a tungsten coil vaporizer, a simple computer controlled power supply with high reproducibility of the output voltage and a fast and efficient data acquisition and processing system for the short transient signals. Coupling the ETV system with the spectrometer and control of additional functions were performed by means of an interface connected to the ETV computer, allowing operation with a high degree of automation. The ablation of tungsten in the vaporization step could be significantly reduced by coating the coil with tungsten carbide and by a decrease in the concentration of traces of oxygen in the Ar–H2 carrier gas using a high-voltage discharge cell. The tungsten ablation was investigated for aqueous solutions and also for silicon carbide as an example of a refractory matrix. The transport losses of the analyte elements Au, As, Ca, Cr, Cu, Co, Fe, La, Mn, Na, Sb and Sc were determined for several matrices by means of the radiotracer technique. Transport losses were found to be in the range from 7% (La) to 54% (Cu).

Development of an automatic ion beam focusing system for a nuclear microprobe

If a nuclear microprobe with a beam size in the submicron region is to be attained, an objective measure of beam profile is a prerequisite. We have developed an automatic beam-focusing system for the Lund achromatic lens system. Using a knife-edge method, projections of the beam profile are determined. The resolutions of the measured profiles are then used as feedback in an automatic focusing procedure which uses computer-controlled power supplies for the electrostatic and magnetic focusing lenses. The beam spot size is minimized using a modified SIMPLEX iterative method. The system can use signals from any detectors, which permits it to be used informing the highest resolution microbeams.

Optimization and redesign of an electron spectrometer for high-resolution gas phase UV photoelectron, Auger electron, and ion fragment spectroscopy

Extensive modifications of an electrostatic electron spectrometer of the hemispherical type are described. The purpose of the modifications is to make the instrument more suitable for high-resolution gas phase spectroscopy. The changes concern substitution of electrical adjustments for mechanical precision, improved flexibility in focusing, and a new system of computer-controlled power supplies and detector interface. The instrument is also used for energy analysis of positive ions. Conversion between positive and negative particle analysis is achieved simply by reversing the polarities of all relevant voltages by a number of switches. A gas cell with internal heating is described. The influence of gas cell conditions on resolution is briefly discussed. The computer programs used for spectrometer control, data acquisition, spectrometer optimization, and calibration are described.

A Computer Controlled High Voltage Equipment for Capillary Electrophoresis and Electrochromatography

Abstract An equipment is designed and evaluated for the separation of biomolecules by capillary electrophoresis and electrochromatography. the major components of the equipment are: (a) a high-voltage dc power supply with reversible polarity output, (b) a computer controlled power supply and data acquisition interface using an IEEE-488 General Purpose Instrumentation Bus, and (c) a chromatography system

Multipolar magnet for low-frequency ESR imaging (with computer controlled power supply)

Low-frequency ESR imaging requires field configurations which are difficult to obtain using traditional electromagnets. Multipolar magnets represent a convenient way to obtain both the main magnetic fields and two of the three gradients necessary for a 3D image reconstruction. The authors present the first experimental implementation of this design in the form of a 16-pole electromagnet of cylindrical symmetry, with an aperture of 27 cm and a length of 60 cm. To achieve a given field profile the currents at each pole must be individually controlled and the whole experiment must be under computer control. The power supply consists of 16 bipolar sections that deliver 10 A through a load of 3.7 Omega . The field is sensed by Hall probes at the 16 pole positions and this information is used to correct the field. Details are provided of the power supply and of the interface between power supply and computer.

A system of autonomous, intelligent voltage supplies based on a serial bus (electron spectroscopy application)

A system of autonomous, computer-controlled power supplies is described in which each voltage is programmed by a local Z8671 microcontroller. Programming information is generated by a remote host computer according to a specified format on a common RS232 bus, and local intelligence decodes information on the bus to determine the output voltage of one or more power supplies. The new system is capable of providing unipolar voltages up to a maximum of +or-500 V, together with bipolar voltages up to +or-150 V. These potentials may be programmed manually or controlled via high-level software from the host, allowing each supply to operate in a number of different modes under the independent supervision of each local microcontroller. Facilities available include the ability to download complex voltage profiles into the memory of one or more supplies, the automatic ramping of one or more voltages between predefined limits and synchronisation of the update of voltage supplies, either with each other or with external events.

A versatile computer-controlled power supply for generating complex voltage profiles

A computer-controlled, floating power supply is described which is capable of generating a wide variety of complex voltage profiles. The power supply has been successfully used to provide voltages with quadratic and polynomial forms in order to extend the focus range of a zoom lens in a high-resolution electron impact spectrometer.