Study On TMR-Cantilever Composite High Sensitivity Current Sensor

With the development of technology and the progress of society,electrical signals have become an indispensable element in scientific research,national defense,industrial production,people's lives,the national grid,precision instrument as well as other fields.And it carries very important roles in energy transmission and information communication.Among various electrical parameters(such as current,voltage,capacitance,inductance,etc.),current is the most basic and most important electrical parameter.It is widely used in artificial intelligence,industrial production,aerospace,and the environment monitoring.The current sensor has been developed as a detection device for many years,its principles and forms are diverse,and each has its own application field and occasion.In recent years,current sensor based on magnetoresistive effect(MR)develops rapidly with the advancement of semiconductor technology,among them,sensors based on tunnel magnetoresistance(TMR)elements have gradually become a research hotspot in the field of sensors at home and abroad due to their better temperature stability,wider linear range,low power consumption,simple structure,low cost,and superior overall performance.This paper is aimed at the field of high-precision current detection.Based on the disadvantages of the existing current sensor,such as weak detection stability,complex system structure,and difficulty in achieving non-intrusive detection of multi-line cables.We combine TMR with a cantilever beam to design a TMR-cantilever composite current sensor for the first time.And it can realize high-sensitivity and high-linearity current detection by constructing its force-magnetic coupling theoretical model.On this basis,the current sensor can be further structurally optimized to form a self-powered current detection system.In the structure of the current sensor designed in this paper,it is mainly composed of two units.One is the TMR as a sensing unit and the other is a cantilever with a permanent magnet fixed at the free end as a non-linear amplification unit.Then we explore the deformation law of the cantilever beam under the excitation of DC and AC currents,and study the distribution characteristics of the magnetic induction intensity of the cuboid permanent magnet to determine its linear detection interval,in order to obtain the change rule of the magnetic induction intensity that the TMR receives after the spatial position of the permanent magnet changes.Finally,the mathematical model between the current to be measured and the TMR output voltage is established.In the experimental results,it is verified that the current sensor designed in this paper can improve the sensitivity by an order of magnitude compared with the traditional TMR current sensor,and has good linearity.On this basis,we explore the influence of the distance variables and the size variables on the output voltage of the current sensor,and briefly analyze the difference in experimental results.Because the power required by the designed TMR circuit is in the milliwatt level,we can optimize the structure of the current sensor so that energy collection can be performed while realizing high-sensitivity current detection.Then a self-powered detection system can be formed.In the modeling process,it is found that the current detection can also be achieved by using a piezoelectric cantilever beam.Then we explore the nonlinear error due to the nonlinearity of the magnetic field gradient,design an error suppression scheme,and verify its effectiveness through experiments.In this paper,the current weak magnetic field drives the permanent magnet strong magnetic field to move in space to achieve high-sensitivity current detection,which has certain reference significance in the field of current sensors.