Dynamic Current Measurement Research Articles

Galinstan Liquid Metal Electrical Contacts for Monolayer-Modified Silicon Surfaces.

Galinstan is the brand name for a low-melting gallium-based alloy, which is a promising nontoxic alternative to mercury, the only elemental metal found in the liquid state at room temperature. Liquid alloys such as Galinstan have found applications as electromechanical actuators, sensors, and soft contacts for molecular electronics. In this work, we validate the scope of Galinstan top contacts to probe the electrical characteristics of Schottky junctions made on Si(111) and Si(211) crystals modified with Si-C-bound organic monolayers. We show that the surface-to-volume ratio of the Galinstan drop used as a macroscopic contact defines the junction stability. Further, we explore chemical strategies to increase Galinstan surface tension to obtain control over the junction area, hence improving the repeatability and reproducibility of current-voltage (I-V) measurements. We explore Galinstan top contacts as a means to monitor changes in rectification ratios caused by surface reactions and use these data, most notably the static junction leakage, toward making qualitative predictions on the DC outputs recorded when these semiconductor systems are incorporated in Schottky-based triboelectric nanogenerators. We found that the introduction of iron particles leads to poor data repeatability for capacitance-voltage (C-V) measurements but has only a small negative impact in a dynamic current measurement (I-V).

Design & Implementation of High Dynamic Range Current Measurement System for IoT Applications

Internet-of-Things (IoT) devices have a strict necessity for power consumption to achieve the expected battery life. Therefore, measuring and optimizing the energy consumption of IoT nodes are essential. IoT nodes feature extreme current consumption range over <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\mathrm {100}}~\text {dB}$ </tex-math></inline-formula> between their operating modes. The main focus of this article is to design and implement a low-power and low-cost current measurement circuit, which can be integrated into IoT nodes. A new pass element is introduced for measuring the current consumption. This element is placed in the current path to measure current over a high dynamic range with a constant voltage drop. The introduced pass element consists of a capacitor and analog switches. The current consumption is measured based on the charge and discharge times of the capacitor in the specified period of time. The voltage across the pass element is buffered and fed to a low-power microcontroller. The proper operation of the proposed circuit is verified numerically with simulations and experimental measurements. The implemented current measurement circuit offers a load regulation of 0.23%, a dynamic range of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\mathrm {173.98}}~\text {dB}$ </tex-math></inline-formula> , and a linearity error of 0.522%. It is expected that the proposed system provides clear information on the power behavior of IoT devices, which can be used for power optimization of IoT networks and self-power test equipment.

Research and Application on GMR Current Sensing Technology

With the development of smart grid, and ever-increasing kinds of electrical loads, the power system requires current measurement technology with wider measurement range, this thesis designs a new type of current sensor based on Giant magnetoresistance (GMR) material. Firstly, this thesis introduces principles and characteristic of GMR current sensor. For the shortcomings of low sensitivity and poor linearity of GMR chip, this thesis presents a structure of open-loop current sensor using GMR chip as magnetic probe, which improves the sensitivity of sensor effectively. Based on the open-loop GMR current sensor structure, a closed-loop GMR current sensor design is proposed. This design compensates the magnetic field through the feedback circuit and improves the accuracy and dynamic measurement range of GMR current sensor. Finally, we tested the GMR sensor system we developed, include DC characteristic test and AC characteristic test, it shows the current sensor has the capability of high dynamic current measurement.

Three channel high dynamic current measurement system for low power systems

The measurement of the dynamic power consumption is a very important task for the characterization and optimization of an energy-autonomous system. In this paper a measurement system is presented that allows the simultaneous measurement of three current ranges from 1 µA to 30 mA at a sample rate of 1 MHz with a selectable supply voltage in the range of 1.8 V to 3.3 V. With this system the full range of low to high power consumption is covered with a high resolution in time, as it is present in a wireless sensor node during data acquisition and wireless communication, respectively.

Detection of charge dynamics of a tetraphenylporphyrin particle using GaAs-based nanowire enhanced by particle–metal tip capacitive coupling

We investigate a detection technique of charge dynamics of a molecular particle using a GaAs-based nanowire where the charge sensitivity is locally enhanced by particle–metal tip capacitive coupling. By equivalent circuit analysis, it was clarified that the nanowire channel potential becomes sensitive to the molecular particle on the nanowire when the particle is capacitively coupled with a metal tip. The concept was demonstrated using a GaAs-based nanowire with tetraphenylporphyrin (TPP) particles on its surface and a measurement system integrating an atomic force microscope (AFM) and a dynamic current measurement monitor/spectrum analyzer. When the metal tip was in contact with a TPP particle on the nanowire under an appropriate tip bias condition, random telegraph signal (RTS) noise was imposed on the nanowire current, suggesting the increase in sensitivity to the charge state of the particle by the metal tip contact. We discussed the origin of the RTS noise through analysis of the time constant of RTS noise, RTS amplitude, and noise spectrum.

Rogowski Coil for Current Measurement in a Cryogenic Environment

Abstract A Rogowski coil based sensor for current measurement in a cryogenic environment and results of its application for paralleled high temperature superconducting (HTS) coil current sharing are presented. The current sensor consists of a Rogowski coil and an integrator, where the coil output voltage is proportional to the derivative of primary current and the integrator transfers the differentiation to normal state. The Rogowski coil has promising applicability at cryogenic circumstance because its body is made of low temperature materials. The integrator ensures a large bandwidth with feasible magnitude, which is vital for dynamic current measurement during the quench of the HTS coil. The proposed current sensor is used for current sharing measurement of two paralleled Bi2223 HTS coils, and the experimental results show that the measurement precision is better than 0.5%.

Design and implementation of a voltammetry potentiostat with wide dynamic current range measurement for electrochemical biosensors

In this paper, we design a voltammetry potentiostat chip with wide range current measurement for the signal processing of electrochemical biosensors. In this design, the current of biosensors will be detected and divided into four regions, and then be diminished in accordance with corresponding current scaling ratio. All the ranges of the biosensor's current will be diminished to a proper current range (≤2.5 μA) and then be converted into frequency-modulated pulses by a sigma---delta modulator in a fixed conversion time. The aim of this design is to deal with the large dynamic current range of signal processing for different biosensors in applications. The measured results of proposed potentiostat can be digitized by a microprocessor without using a high resolution ADC. The proposed potentiostat is fabricated by 0.35 μm CMOS technology, and the chip layout core area is 0.31 mm2. The function of the proposed potentiostat has been tested and measured in our laboratory, and the measurement results show that the dynamic range of signal processing, from 1 nA to 2 mA, is 126 dB. The power consumption under normal operation is 10 mW. The proposed voltammetry potentiostat has successfully applied to the signal processing system of a melatonin biosensor.

Fast and wide-band response infrared detector using porous PZT pyroelectric thick film

Porous lead zirconate titanate (PbZr0.3Ti0.7O3, PZT30/70) thick films and detectors for pyroelectric applications have been fabricated on alumina substrates by screen-printing technology. Low temperature sintering of PZT thick films have been achieved at 850°C by using Li2CO3 and Bi2O3 sintering aids. The microstructure of PZT thick film has been investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The dielectric properties were measured using HP 4284 at 1kHz under 25°C. The permittivity and loss tangent of the thick films were 94 and 0.017, respectively. Curie temperature of PZT thick film was 425°C as revealed by dielectric constant temperature measurement. The pyroelectric coefficient was determined to be 0.9×10−8Ccm−2K−1 by dynamic current measurement. Infrared detector sensitive element of dual capacitance was fabricated by laser directly write technology. Detectivity of the detectors were measured using mechanically chopped blackbody radiation. Detectivity ranging from 1.23×108 to 1.75×108(cmHz1/2W−1) was derived at frequency range from 175.5Hz to 1367Hz, and D*’s −3dB cut-off frequency bandwidth was 1.2kHz. The results indicate that the infrared detectors based on porous thick films have great potential applications in fast and wide-band frequency response conditions.

Diagnosis of OLTC via Duval Triangle Method and Dynamic Current Measurement

Power transformers studies have shown that the main cause of power transformers failures is the On Load Tap Changer (OLTC). OLTC failure occurs due to the insulation degradation and contacts failure inside it. Other than that, contacts wear influences the OLTC performance and this phenomenon has not been deeply investigated. The worn contacts will cause hotspots in the OLTC tank and cause the insulating oil to degrade faster. Consequently, this will lead to the damage of complete transformer unit. Thus, the research work that has been carried out applied three different stages related to the diagnosis of OLTC. Firstly, fault detection of power transformer's OLTC is done mainly based on the results of the DGA interpretation by using the latest Duval Triangle method. Then, the results that obtained from latest Duval Triangle method are compared with the results carried out from Dynamic Current Measurement (DCM). Finally, research validation through visual inspection is applied to validate the results obtained from both DGA and DCM.

Dynamic Prebreakdown Current Measurement of Nanotips-Based Gas Ionization Sensor Application at Ambient Atmosphere

A gas ionization sensor (GIS) with nanotips as anode and tungsten needle as cathode was fabricated, which is working with moderate input voltage. Controlled dc voltage was applied, and the prebreakdown currents were measured. The sensor can be used to determine target gases at ambient atmosphere. A novel dynamic prebreakdown current measurement was exploited which can decrease the noise interference and improve the stability of the GIS. It is discussed in detail about the advantages of the dynamic prebreakdown current measurement and its influence factors. In addition, carbon nanotubes and zinc oxide nanorods were used as ionization tips, respectively. Their anti-oxidation performances were indicated by experiment.

Deconvolving Current From a Faraday Rotation Measurement

In this paper, a unique software program is reported, which automatically decodes the Faraday rotation signal into a time-dependent current representation. System parameters such as the Faraday fiber's Verdet constant and the number of loops in the sensor are the only user-interface inputs. The central aspect of the algorithm utilizes a short-time Fourier transform, which reveals much of the Faraday rotation measurement's implicit information necessary for unfolding the dynamic current measurement.

Peculiarities of electron tunnel injection to the drain of EEPROMs

A specific time-resolved dynamic current measurement procedure is used to characterize high-field electron tunnel injection to the drain of EEPROMs. This allows the direct observation of a transient regime eventually occurring in the case of moderately doped drain. Another peculiarity is also evidenced, namely a stationary regime where measured current is far higher than anticipated by simulation. This is attributed to a non-equilibrium charge versus band-bending in the drain which is controlled by electron–hole pairs subsequent to impact ionization of electrons tunnelling from the gate.

Experimental confirmation of an accurate CMOS gate delay model for gate oxide and voltage scaling

MOSFET's and CMOS ring oscillators with gate oxide thicknesses from 2.58 nm to 5.7 nm and effective channel lengths down to 0.21 μm have been studied at voltages from 1.5 V to 3.3 V. Physical and electrical measurement of gate oxide thicknesses are compared. Ring oscillators' load capacitance is characterized through dynamic current measurement. An accurate model of CMOS gate delay is compared with measurement data. It shows that the dependence of gate propagation delay on gate oxide, channel length, and voltage scaling can be predicted.

Formation of palladium oxides by mechanochemical reaction on Pd and Ag-Pd alloy contacts

The authors have already reported that when Pd contacts are operated in mechanical break-make actions without switching load current in air (laboratory atmosphere), palladium oxides are formed on the contact surfaces by a mechanochemical reaction and cause a marked increase of contact resistance. The formation of the same products on Ag-Pd 70% and Ag-Pd 50% contacts after tests involving 100000 operations are reported. Significant increase of contact resistance, however, was not observed. However, nonlinearity of contact resistance, as revealed by both dynamic and static current measurement, was observed. Temperature calculation shows that softening of the electrodes is not the main reason for the phenomenon. Other reasons, such as thermal dissolution of the contaminant layer, are suggested instead.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>