DC Current Measurement Research Articles

Research on Modulation Method and Characteristic Analysis of Faraday DC Optical Measurement System

The optical current transformer is an important content in smart grid research field. When the Faraday DC optical measurement system was used in DC current measurement, the low frequency noise caused by photo detector and measured signal were overlapped, which makes the measuring accuracy decrease. To solve this problem, the noise of photo detector is analyzed. Then, the frequency modulation is proposed for spectrum shifting. Furthermore, the principle of modulation method is deduced in formula, and the characteristics of deferent frequency are also analyzed. On this base, modulation signal source is designed. With LabVIEW program, the signal from modulation source is acquainted and analyzed. The results show that this modulation method can realize spectrum shifting and the designed signal source is able to generate waveform needed.

Damage identification in carbon fiber reinforced polymer plates using electrical resistance tomography mapping

This study addresses the issue of structural damage identification and location in carbon fiber reinforced polymer plates using electrical measurements. Electrical resistance tomography is presented as a method for structural damage localization in composite parts. A set of electrodes is fixed on the edges of the part and combinations of DC current injections and voltage measurements are applied to the system. The change of voltage between different times in the part’s service life (e.g. start and degraded) are monitored. These sets of measurements are used as input to inversely calculate conductivity maps for the complete composite part and thus indirectly assess its structural health. Such processes are inherently ill-posed. Data post-processing approaches are proposed here to diminish this uncertainty and to conclude to an optimally converge solution of the inverse problem. To assist the process, a material-originating mathematical constraint is introduced. The method is applied on carbon fiber reinforced polymer plates for different damage modes. Experimental recordings show that the analysis of electrical fields allows detecting the presence of damage. Discontinuities as small as 0.1% of the inspected area can be sensed. The proposed data post-processing techniques were applied and conductivity maps were calculated. The results show that using these techniques locating damage is possible with less than 10% error. Material-based constraints greatly enhance the prediction of the data post-processing techniques. It is believed that by overcoming certain implementation issues, electrical resistance tomography could evolve in the direction of a non-destructive evaluation or a structural health monitoring technique for composite structures.

Neel Effect current sensor featuring double core toroidal topology

A Neel Effect® current sensor featuring a double toroidal core is proposed. The measurement relies on the application of a harmonic excitation to the magnetic core and on the sensing of the magnetic flux density variations in the presence of a current to measure. The principle of a device designed so as to perform both those operations by means of the same winding is presented and validated experimentally. The measurement of DC currents is carried out over the [−200–200 A] range under different excitation conditions.

Single-crystal magneto-optic sensor with electrically adjustable sensitivity

A novel magneto-optic sensor with electrically adjustable sensitivity is proposed that is based on the approximate multiplication correlation between the linear electro-optic phase retardation and the Faraday magneto-optic rotation angle in a single bismuth germanate crystal. The measurement sensitivity and its temperature stability, linear and monotonic measurement ranges of the proposed sensor can be controlled in real time by adjusting the modulating voltage applied to the sensing crystal. In particular, the proposed sensor can be used for the precise measurement of dc magnetic field or dc current. The basic sensing performance is theoretically analyzed and experimentally demonstrated by dc current measurement.

MOSFET threshold voltage: Definition, extraction, and some applications

This paper exploits a universal current-based definition of the threshold voltage (VT) and discusses some direct methods to measure it. The consistency, accuracy, and sensitivity of the extraction procedures to second-order effects are examined through numerical simulations and experimental measurements. In addition to three procedures based on dc current measurements we propose an automatic VT-extractor circuit which allows the direct determination of the threshold voltage with minimum influence of second-order effects.

A High Dynamic Range GMI Current Sensor

The design and performances of a high dynamic range DC-AC current sensor utilizing Giant Magneto-Impedance (GMI) are presented. The sensor is based on a GMI element with negative feedback. The sensing element is a 30 μm diameter GMI Co-based amorphous wire. It is curled to a toroidal core of 2 cm diameter. A bias magnetic field of about 650 A/m is applied to the GMI element to obtain an asymmetric GMI effect. A strong negative feedback is introduced to ensure linearity in a wide dynamic range. Analog conditioning electronics was fully developed. This includes a square wave oscillator based on an inverter trigger; a peak detector and a high gain amplifier with zero adjust. The GMI element is driven at a 3 MHz frequency and 5 mA peak-to-peak current. The closed-loop operations are investigated and the performances of the sensor are presented. DC current measurements are performed. The sensor exhibits good sensitivity and very good linearity, free from hysteresis, in a wide dynamic range of ±40 A. The sensitivity is about 0.24 V/A and the linearity error is about 0.02% of the full scale (FS). The hysteresis error is smaller than the measurement accuracy. AC current measurements using the developed sensor have also been successfully achieved. The sensor bandwidth in closed-loop was about 1.7 kHz.

Electrical test method using high density plasmas for high-end printed circuit boards

A novel electrical test method that uses high-density plasmas, such as inductively coupled discharges, is proposed to detect open/short failures of high-end printed circuit boards (PCBs). The PCB is inserted into the plasma chamber with the top side facing the plasma sheath, and the bottom of the PCB is connected to the probe pin for the dc voltage bias and current measurements. A failure, including a latent open, can be precisely detected by biasing the dc voltage near the plasma potential due to the specific characteristics of the sheath formed on the PCB surface.

Research of DC Current Measurement Technology Based on Optical Fiber Thermometry

Thin film sensor has the advantages of small size and low cost, which has become a research hotspot in recent years. A measurement system of passive optical fiber DC current sensor based on the thin film sensors is designed in this article. Designs of electric-heating converter, heating-light converter and low-voltage measurement display system are introduced in detail. Experimental results indicate that the general linear correlation between the time constant of fluorescent lifetime and the voltage across the thin film resistor. The feasibility of measurement system is verified via the results of the experiment.

Transresistance calibrations and temperature dependence evaluation of a magnetic bridge current sensor with shunt standards

This paper deals with a magnetic bridge current sensor for dc current measurements and a calibration system developed for the current sensor. The current sensor forms a magnetic bridge structure with a magnetic fluid core. The calibration system has been developed by using standard shunts for a test current range of 1 mA to 100 A and establishing a comparison method with a switching/sampling system. In the calibration system, the transresistances of the current sensor are measured and the uncertainties of the system are estimated for the input test current range. Also, the temperature dependence on the transresistances is investigated for temperatures ranging from −40 to 100 °C.

Study of electrical and optical properties of CN x thin films deposited by reactive magnetron sputtering

The study concerns the CN x thin films deposited by Low Pressure Hot Target Reactive Magnetron Sputtering (LP-HTRMS). The thin film resistance changes with relative humidity (RH) and optical properties have been studied in the range of 300–653 K. The temperature coefficients of resistivity changes were −2.5%/K at 300 K and −0.5%/K at 500 K. The activation energy of conductivity E ρ was found to be 0.21 eV in the case of unannealed sample and 0.44 eV when the sample was annealed at 653 K. The CN x thin films fastness to light was tested in the range of 200–2500 nm by measuring their transmittance. The calculations of absorption carrying out with Tauc formula proved the dominance of indirect optical transitions with Eg energy of 1.04 eV and direct transitions of Eg 2.05 eV. The UV radiation was fully absorbed and light transmission was ca. 90% in the range from visible radiation to far infrared of 1000–2500 nm. The CN x thin films showed the high resistance sensitivity to RH changes. At T = 300 K resistance changed from 882 M Ω for 36% RH to 386 k Ω for 85% RH. The CN x thin films susceptibility to humidity was observed in case of both DC and AC current (100 Hz to 10 kHz) measurements. The Si 3N 4 or SiC buffer adhesive layer was incorporated between CN x film and substrate and its influence on CN x electrical properties was observed.

Design of a Low-Consumption Fluxgate Transducer for High-Current Measurement Applications

This paper presents the design and final realization of a transducer system for the measurement of high dc and ac currents. This transducer is based on the magnetic flux compensation technique, also called fluxgate principle. The transducer designed can measure currents of around 1 kA of peak value with a 170-kHz small-signal bandwidth. This functionality can be achieved with low power consumption if the designed system is compared with other fluxgate transducers available on the market and with similar functional specifications. Improvement in consumption was achieved by the inclusion in the design of a switching power supply (based on flyback topology) and a switched amplifier for generating magnetic flux compensation current (based on half-bridge inverter topology).

The Design of a Hall Effect Current Transformer and Examination of The Linearity with Real Time Parameter Estimation

Today, the Hall sensor based current measurement is being widely used as they have both AC and DC current measurement capability. The factors such as ratiometric error of Hall sensor, earth or other magnetic effects in sensor location, sensitivity errors originating from temperature or magnetic core, deteriorates measurement linearity. This requires that measurement results are evaluated with mathematical analysis methods. In this study, a closed loop Hall Effect current transformer was designed and its linearity in measurement results is examined by real time parameter estimation based on the least squares method so measurement accuracy was improved and real time observation of linearity error was provided.

Focus on magnetics and electromagnetism

Focus on magnetics and electromagnetism

Study of minority carrier injection phenomenon on Schottky and plasma deposited p–n junction diodes

Both temperature dependent ac capacitance ( C) together with ac conductance ( G) under various frequencies ( ω) and dc current ( I) measurements as functions of bias ( V) were employed to investigate majority as well as minority carrier injection phenomenon on chromium-p-type crystalline silicon (Cr/p-cryst. Si/ohmic contact) Schottky and aluminum/plasma deposited n-type hydrogenated amorphous silicon/p-c-Si (Al/n-a-Si:H/p-c-Si/ohmic contact) p–n structures. Ambipolar transport process was eventual for both diodes and behaved differently according to the mentioned techniques: for a well defined forward bias interval, there was an increase in capacitance towards maximum that interpreted as majority carrier injection from the back electrode. On the other side, minority carrier injection from front electrode begun when the bias went beyond the critical voltage (i.e., built-in voltage) that corresponded to the peak position and caused sharp decrease in measured capacitance, leading to observation of a hump in C– V measurement. Moreover, shape and peak position of the hump were frequency/temperature dependent. Remarkably, in the bias range where capacitance pronounced, space charge limited current (SCLC) was discerned as enrolled carrier flow mechanism according to I– V measurement, confirming further majority carrier injection. In addition, both dc conductivity and ac conductance followed the same dependence with bias voltage in forward direction. On the other side, reverse current seemed proportional to square root of reverse bias, implying generation current in the depletion region. These experimental identifications convinced us of the existence of conductivity modulation issue for the structures at hand.

Electrical transport mechanism in boron nitride thin film

Both dc and ac transport characteristics of plasma enhanced chemical vapor deposited (PECVD) boron nitride (BN) thin film was investigated by dc current vs. dc voltage measurement at different temperatures and admittance vs. gate voltage at various frequencies/temperatures, respectively. MIM ≡ metal (Al)-insulator (BN)-metal (Al) or MIS ≡ metal (Al)-BN-semiconductor (p-Silicon) test devices were conventionally produced. Both conductivity anisotropy and dc/ac detailed transport mechanism were analyzed within the frame of a turbostratic structure (t-BN), interfacing the substrate by a thin amorphous layer (a-BN). This defective BN film has been justified by both infrared (IR) analysis and indirectly by the resulting electrical transport behavior. Transport and its variations as a function of temperature/frequency are in agreement with a hopping mechanism across Gauss-like energy distributed localized deep traps.

ANALYTICAL AND NUMERICAL ANALYSES OF A CURRENT SENSOR USING NON LINEAR EFFECTS IN A FLEXIBLE MAGNETIC TRANSDUCER

A theoretical study and a simulation method are proposed for superparamagnetic current sensors implementing a uniformly wound toroidal core topology. So as to be easy to implement, this sensor topology can be made ∞exible thanks to the use of a core made up of a superparamagnetic powder embedded in a ∞exible plastic matrix. The measurement of DC and AC currents is possible provided that a sinusoidal magnetic fleld excitation is applied to the superparamagnetic transducer. An analytical model is proposed for computing the sensor output signal and we demonstrate that when the detection of the component at the second order harmonic of the excitation frequency is used, the measurement is independent of the conductor position in a given current range. For simulating the dynamic response of the sensor, we propose to combine the analytical model, or a flnite elements model, with a time-discretization method. Furthermore, simulations are carried out considering a ring shaped sensor and the real magnetization characteristics of a superparamagnetic material. Simulations are provided over the (i10kA 10kA) range and for various amplitudes of the excitation signal. The results obtained with the analytical model, which is computationally e-cient, are within 4% to 12.7% from the numerical results.

SPECTRAL AND STATISTICAL ANALYZING OF HALLEFFECT CURRENT TRANSFORMERS

Although the Hall Effect has been known for over one hundred thirty years, it has only been put to noticeable use in the last four and half decades. It has ability both AC and DC current measurement, converting magnetic flux to voltage so that it has many application fields. The Most importing fields of them are current and power sensing, magnetic field sensing and distance measurement. In this study, statistical and power spectrum of AC voltage of the Hall Effect current transformer were analyzed. According to calculated statistical parameters, it is seen that variation is Non-Gaussian distribution and includes all frequencies in 0-1 kHz range. Spectrum variation was analyzed about 0,1 Hz.

Poly(dimethylsiloxane)-Based Protein Preconcentration Using a Nanogap Generated by Junction Gap Breakdown

Simple and efficient sample concentration tools are the key to the application of proteomics in a biological system. In this paper, we developed a method to realize a nanofluidic preconcentrator on a poly(dimethylsiloxane) (PDMS)-based microfluidic channel. The originality of our preconcentration device is the simple nanogap formation using the junction gap breakdown phenomenon between two PDMS microchannels, without using any photolithography and etching techniques. From the dc current measurement, we confirm that the nanogap formed between two microchannel junctions with approximately 80 nm depth. Using this device, we achieve the concentration volume of beta-phycoerythrin protein as high as 70 pL, which is 120-fold larger than that from our previous reports, with a concentration factor as high as 10(4) within 1 h. Also we show the availability of protein preconcentration under several different buffers (phosphate, acetate) at several different pH values (pH 5 to pH 9).

New Capability for Generating and Measuring Small DC Currents at NPL

This paper describes two systems recently developed at the National Physical Laboratory (NPL), Teddington, U.K., for the generation and measurement of dc currents in the range 100 fA to 1 nA. Both systems are based on the capacitor charging technique. One system generates known currents, and constitutes a new reference at NPL. The other was designed to meet the traceability requirements of the Ionizing Radiation sections of NPL and combines commercially available instrumentation and standards to produce a reliable stand-alone system for measuring small currents

Magneto-optic sensor by use of time-division-multiplexed orthogonal linearly polarized light

A magneto-optic sensor is proposed and experimentally demonstrated. The sensing unit is mainly composed of an electro-optic modulator, a Faraday magneto-optic glass, and two polarizers. Different from the conventional magneto-optic sensors, this sensor utilizes a time-division-multiplexed and alternately polarized light carrier whose azimuthal angle is periodically alterable between two orthogonal linear polarization states. In particular, this sensing scheme is suitable for dc magnetic field or current measurement, and the measurement result is free from the influences of light intensity fluctuation and environmental electromagnetic interference, due to the applications of square-wave modulation and lock-in amplification techniques. The dc magnetic field in the range of +/-(0.067 approximately 20) mT has been remotely measured and the nonlinear error is less than 1.0%.