Oleg Petruk

Sensitivity and Offset Voltage Testing in the Hall-Effect Sensors Made of Graphene

Paper presents the results of the hall effect testing in the graphene structures. Special hall effect structures were designed and build, using large graphene sheets. Laboratory testing stand was developed to test sensitivity and offset voltage in hall effect structures under external magnetic field. Characteristics of investigated structures were measured, including such impacting factors as structure size, external magnetic field strength, temperature and time.

Low-noise epitaxial graphene on SiC Hall effect element for commercial applications

In this report, we demonstrate a complete Hall effect element that is based on quasi-free-standing monolayer graphene synthesized on a semi-insulating on-axis Si-terminated 6H-SiC substrate in an epitaxial Chemical Vapor Deposition process. The device offers the current-mode sensitivity of 87 V/AT and low excess noise (Hooges parameter αH < 2 × 10−3) enabling room-temperature magnetic resolution of 650 nT/Hz0.5 at 10 Hz, 95 nT/Hz0.5 at 1 kHz, and 14 nT/Hz0.5 at 100 kHz at the total active area of 0.1275 mm2. The element is passivated with a silicone encapsulant to ensure its electrical stability and environmental resistance. Its processing cycle is suitable for large-scale commercial production and it is available in large quantities through a single growth run on an up to 4-in SiC wafer.

Digitally Controlled Current Transformer with Hall Sensor

Paper presents the digitally controlled high resolution DC current transformer enabling contactless measurements of DC current. To increase the sensitivity of current transformer, high permeability, amorphous alloy based ring-shaped core was used. Moreover, analyses of magnetic field distribution in the measuring gap were carried out. Magnetic field in this gap was measured by the hall sensor connected with the high resolution sigma-delta analog to digital converter. As a result, current up to 100 A may be measured with uncertainty of about 1A.

Adaptive Control of Dynamic Load in Blooming Mill with Online Estimation of Process Parameters Based on the Modified Kaczmarz Algorithm

This paper considers approaches of solving actual task of reducing dynamic load of lines in the blooming mill during rolling, which occurs due to a number of uncontrollable factors. An approach that combines modified Kaczmarz algorithm and robust algorithm of speed gradient is employed to estimate past and current values of the state, provide dynamic compensation of uncertainties and changes of control object parameters during metal compression on blooming, as well as to form adaptive control law for solving the problem of reducing the dynamic load in working rolls of blooming mill. Analysis of the results of simulation of proposed methods has shown high efficiency of transient processes with provision of opportunity to compensate dynamic changes in parameters of the research object during exploitation.

Torque and Capacity Measurement in Rotating Transmission

The task of measuring, monitoring and recording of the torque, mechanical stress and capacity is relevant for most transmissions of the process and transport machines. The importance of this problem is increased by an order in terms of unsteady loads (random, impulsive, alternating, etc.). The disadvantage of its correct solution by experimental methods is substantially limited by the need for expensive and unreliable, environmentally dangerous current collectors. To measure the dynamic and kinematic parameters of the rotating transmission by modern information computer technologies, we propose equipping the mechanical transmission with two additional half-couplings with point magnets fixed thereon, the scope of each includes one or more Hall sensors. The application of the developed technique allows determining the torsional rigidity of the transmission experimentally, and allows recording the actual torque and capacity per turn (or a part of the turn) of the transmission of a process or transport machine and record the same online in the computer electronic memory. This, in turn, allows an online assessment of the residual transmission resource, machine operation per shift and generate its operation history, which provides an invaluable information both to the machine developer and owner.

Advancement in Development of Graphene Flow Sensors

This article describes the research, development and tests of prototype graphene flow sensors. The prototype sensors were checked for impact of different parameters on value of electric charge generated on the graphene’s surface, such as volume flow value, flowing liquid ions concentration and liquid temperature. The information about developed transducers which convert signals from graphene sensor is presented.

Temperature Dependence of Functional Properties of Graphene Hall-Effect Sensors Grown on Si Face and C Face of 4H-SiC Substrate

Paper presents the results of investigation of the temperature influence on the basic functional properties of graphene Hall-effect sensors. The measurement system utilizing Helmholtz coils as a source of external magnetic field and environmental chamber for setting temperature was developed. Two types of monolayer graphene structures grown on both Si and C face of SiC substrate were investigated in the room temperature (about 20 oC) and their functional properties were compared. Next, the temperature influence on functional properties of both types of graphene structures was investigated using environmental chamber. The results of measurements are presented as charts and analyzed in the paper. On the basis of the results, conclusions were formulated, which are included in the last section of the paper.

Measuring Station for Testing of Graphene Flow Sensors

This article describes the construction and operation principle of a measuring station for testing of prototype graphene flow sensors. The measuring station enables for checking an impact of different parameters, such as volume flow value, flowing liquid concentration and liquid temperature on value of generated electric charge on the graphene’s surface. This paper also presents basic information about developed transducer which converts signals from graphene sensor. The essential part of the text is chapter about tests of the station. It contains information essential for depicting of real conditions during measurements of generated electric charge on the graphene’s surface. Reliability of the carried out research was checked by estimation of uncertainty of measurement equipment.

Investigation on Functional Properties of Hall-Effect Sensor Made of Graphene

Hall-effect sensors are commonly used in many industrial applications as position detectors, incremental counters and sensing elements of DC current transformers. Previously developed Hall-effect sensors utilize InAs or InSb as a sensing material. Recently, graphene seems to be the most promising material. Monolayer graphene was grown using the Chemical Vapor Deposition (CVD) method on the substrates. Prior to the growth, in situ etching of the SiC surface was carried out in hydrogen atmosphere. Functional properties of developed Hall-effect sensors based on graphene were tested on special experimental setup. Results presented in the paper indicate, that graphene is very promising material for development of Hall-effect sensors. Such sensors exhibit high magnetic field sensitivity and linear characteristic. It was also observed, that functional parameters of graphene Hall-effect sensors are diversified from the point of view of its transport properties. This phenomenon creates important possibilities of further optimization of Hall-effect sensors during their production.

Methodology of Reduction of the Offset Voltage in Hall-Effect Sensors

The paper presents new, original methodology of reduction of the offset voltage in Hall-effect sensors. The outline of innovative Hall-effect sensor with five electrical pins for each electrode is presented. Such a construction creates a possibility to use different combinations of pins in order to find minimum value of the offset voltage. The procedure of searching for the best combination of pins connected for minimization of the value of offset voltage is also presented. For practical implementation of the methodology, special experimental system was developed, utilizing system of relays controlled by Data Acquisition Card to set different combinations of pins and search for the minimum value of the offset voltage. Obtained results indicate that there is a possibility to reduce value of the offset voltage even up to one hundred times.