Development Of Magnetic Susceptibility Tensor Instrument Based On Rotating Method

The magnetic susceptibility is a physical quantity that expresses how easily an object can be magnetized under the action of an external magnetic field,and is an inherent property of a substance.At present,the scalar information of magnetic susceptibility of rock and ore is mostly measured in wells and laboratory measurements.When the susceptibility is used as a scalar,it not only has a significant role in paleomagnetism and rock magnetism,but also has research value in environmental magnetism.For example,with the rapid development of industrialization and the increasing frequency of human activities,soil pollution has become more and more serious,which contains a large number of heavy metal elements,so the magnetic susceptibility is much higher than that of its own.The soil magnetic susceptibility can be measured to judge industrial pollution.However,the scalar information of the magnetic susceptibility is not rich enough to explain the magnetic anomaly of the banded minerals and it is impossible to study the remanence vector of the rock.The susceptibility tensor,as one of the magnetic characteristics of rock ores,contains a lot of information related to geology,geophysics and paleomagnetism.The magnetic susceptibility tensor can be used to quantitatively explain the magnetic anomaly;it can analyze the sedimentary layer,sedimentary environment,foliation,streamline properties,strain stress and structural form of rock and ore,and the magnetic susceptibility tensor measurement can be used as the ground and An important auxiliary method for magnetic exploration in wells.Different from the measurement of the scalar magnetic susceptibility,the magnetic susceptibility tensor measurement is to put the test sample in the sample box,and then measure it around the rotation axis according to the set position to obtain the magnetic susceptibility of the tested sample at different positions.The magnetic susceptibility is multiplied by the rotation matrix to obtain the magnetic susceptibility tensor information.The advantage of the rotation method is that only one sensor is needed to obtain the susceptibility tensor information,which greatly simplifies the complexity of the system.Based on the principle of scalar susceptibility measurement,the thesis derives and verifies the feasibility of the principle of rotation method susceptibility tensor measurement.Then design the measuring circuit and rotating mechanical structure according to the principle of rotating magnetic susceptibility tensor to complete the design and development of the entire magnetic susceptibility tensor.Including sensor design and simulation,measurement circuit design and simulation,rotary motion mechanical structure design,microcontroller design,data acquisition card design and host computer software design,etc.Finally,design and implement ore magnetic susceptibility measurement experiment,susceptibility tensor calibration experiment,ore magnetic susceptibility tensor measurement experiment,magnetic gradient tensor verification experiment and magnetic susceptibility tensor index test experiment.The magnetic susceptibility value of the ore measured by the Czech SM30 susceptibility meter was used to calibrate the susceptibility tensor.The calibrated susceptibility tensor was then used to measure the susceptibility of the iron ore sample.The measurement result was basically consistent with the measurement result of the SM30 instrument.The designed magnetic susceptibility tensor has a measurement range of 5~50000×10-4 SI,and the measurement error is about 4 %.The magnetic gradient tensor data was verified by the magnetic gradient tensor in the experiment,and the magnetic susceptibility tensor value was inverted by matrix calculation,which was consistent with the tensor value measured by the magnetic susceptibility tensor,which once again proved the correctness of the magnetic susceptibility tensor.