Optimization Design And Development Of 1-100kHz Magnetotelluric Induction Coil Sensor

Magnetotelluric instrument is one of the most commonly used instruments in geophysical exploration.Noise level is the core technical index of magnetotelluric inductive magnetic sensor.For a long time,inductive magnetic sensors used in engineering practice in China have been heavily dependent on imports.It is of urgent and strategic significance to study inductive magnetic sensors with independent intellectual property rights.Based on the analysis of signal characteristics of magnetic field component in magnetotelluric field,this paper studies the working principle and structure of inductive magnetic sensor to measure changing magnetic field,and concludes that noise level is one of the core technical indexes of inductive magnetic sensor in magnetotelluric instrument.In order to make an inductive magnetic sensor with low noise,this paper firstly analyzes the distribution of three main noises in different frequency bands.Then,after the design requirements of the sensor are given,the functional relationship between noise and length-diameter ratio and permeability of the magnetic core is constructed,and the optimal lengthdiameter ratio and permeability are calculated to obtain the core quality that meets the design requirements.Then a quality factor is defined,the function relation between noise and quality factor is constructed,and the coil mass is calculated.Under the condition that the coil mass is constant,the second derivative of the total noise is used to obtain the optimal diameter of the wire,and the coil turns parameter is calculated under the condition that the sensor winding ratio is fixed.Finally,a 1-100 khz inductive magnetic sensor was designed and manufactured using the above method.The noise level of the sensor was measured to be more than an order of magnitude lower than the intensity of the geomagnetic field within the frequency range,which proved the scientific nature of the optimal design.Through testing and application cases,the self-designed 1-100 khz inductive magnetic sensor has reached the international leading level.