Research On Non-contacting Detection Technology Of Rotating Shaft Corrosion Current Based On Anisotropic Magnetoresistive Sensor

when the ship sails in the sea,electrochemical corrosion of the steel hulls will occur inevitably for the electric loop formed by the hull and seawater.In order to reduce the corrosion,coating and cathodic protection technology are widely used.Corrosion electrostatic field and extremely low frequency electromagnetic field,collectively referred to as the ship shaft-rate electric field,will be produced on the periphery of the ship with the current,which is generated by the the application of the cathodic protection system.Due to the development of electric field detection and tracking technology,as well as the electric field fuze of mine,we need to reduce the ship electric field produced in the surrounding seawater.At present,the method to reduce the electric field of the ship needs to accurately detect the leakage current of the propeller shaft.However,the range of the measured current amplitude is large,the detection environment is complex,and the interference is large.Therefore,in this paper,we designed a non-contact current detection system with performance of high stability,high precision and anti-interference.According to the principle that the electric field will produce magnetic field in the surrounding space,the magnitude of the measured current can be indirectly reflected by detecting the magnetic field.This method can detect the corrosion current without contact with the propeller shaft of the ship.Comparing the different magnetic field sensors,we chose the AMR(Anisotropic magnetoresistive)sensor with excellent performance and wide application as the transduce of the system.Here we used the dual sensor to detect the current,which can eliminate the common mode interference in the environment.In addiction,the ship propeller shaft current magnetic field is simulated,including feasibility of current detection system,the installation direction of the sensor,the sensor installation width and the errors in the installation process of the experimental results.According to the simulation results,some requirements for the sensor installation were put forward.Then,from the aspects of hardware and software,the design methods of the signal processing and the analog to digital conversion are described in detail.At last,experiment system was set up,and the whole current detection system was verified by experiments.The results show that resolution of the system is 2 mA,the linearity is superior to the full range of 0.5 %,and system can effectively detect the corrosion current of propeller shaft,and the system has good stability,linearity,high resolution,and certain anti-interference ability in the complex measurement environment.