Research On High-Precision And Wide-Band Current Sensing Technology Based On GMR Effect

In recent years,the development of smart grid is in full swing,and the development and popularization of electric vehicles are becoming more and more rapid.The high-precision measurement of high-dynamic current is very important.It is not only related to the economic benefits of the users and the power grids,but also the basis of the intelligent measurement.Based on GMR effect,a new type of current sensor with high precision,wide frequency band,high performance-price ratio and capable of measuring AC and DC current simultaneously is designed and studied in this paper.First of all,this paper compares the advantages and disadvantages of main current sensor products at home and abroad,and highlights the advantages of the giant magnetoresistance(GMR)current sensor in many aspects.By analyzing the selection factors of four kinds of GMR materials and chips,the full bridge GMR chip made of GMR material with magnetic tunneling junction structure is determined,and the bridge structure inside the chip is analyzed.In order to explore the static characteristics of the GMR chip,a static characteristic testing platform for GMR chip is established.The problems of temperature drift,location sensitivity and hysteresis are found through testing,which provide the direction of the key consideration for subsequent design.Because a single GMR chip's measuring position is random and it is easy to be disturbed,an open-loop GMR current sensor is designed in this paper.On the basis of the open-loop structure,the power amplifier circuit and feedback circuit are added,and the closed-loop feedback structure is formed,which increases the measurement range of the current sensor and improves the performance of anti-interference.Then the circuit of the closed-loop GMR current sensor is designed and the preliminary simulation experiment is completed in the circuit simulation software.The hardware structure of the sensor is designed and the sensor is made in real time.And then,the test platform of GMR current sensor is built with the existing equipment in the laboratory.The DC and AC test of the current sensor are carried out respectively.The sensitivity,linearity,precision,range,dynamic response performance and frequency range of the open-loop and closed-loop GMR current sensor are measured.The experimental results show that the closed-loop structure has better linearity and precision than the open-loop structure,and its' measuring range is larger,the frequency band is wider.The dynamic response performance of the open-loop is better,and the purpose of high-precision wideband current sensing is realized.Finally,the application of GMR current sensor in electric energy meter and power measurement is studied.By replacing the original current sensor in the electric energy meter with the GMR current sensor,the comparison test with original electric energy meter is carried on;and the method of adjusting the magnification of the GMR current sensor and adding the shielding cover is tested,and the relative error is reduced.Through the temperature experiment,it is found that the increase of temperature will increase the measurement error to a negative direction,but it is still within the acceptable range,which indicates that the measurement precision of the GMR current sensor has the potential to be applied to the electric energy measurement.The instantaneous power test method using GMR current sensor is analyzed and tested,which provides a feasible scheme for direct measurement of electric energy.