Research On Broadband Low Noise Inductive Magnetic Sensor

Electromagnetic method is one of the main geophysical methods in geological survey,which is widely used in the field of deep crust exploration,earthquake precursor monitoring research,engineering geological exploration and various resources exploration.However,the related technology of inductive magnetic sensor seriously hinders the development,production and application of geophysical and electromagnetic exploration instruments in China.In this paper,a wide-band low-noise inductive magnetic sensor for electromagnetic survey is designed,which has the characteristics of frequency bandwidth and low noise.Research and design of mechanical structure selection and internal circuits have been carried out.Broadband and low noise design are mainly realized in two aspects.In the aspect of mechanical structure selection,the induction coil is wound by a grid winding method to reduce the distributed capacitance and increase the frequency bandwidth.The use of a shielded protective layer made directly from materials with high electrical conductivity reduces the effects of external disturbances on the stability of the system.In the aspect of preamplifier circuit and auxiliary circuit design,JFET discrete amplifier components with high precision and ultra-low noise are selected as the first stage amplifier components for circuit design,and integrated discrete operational amplifier components with low noise and bias voltage are used as the second stage amplifier circuit design to realize low noise amplification of weak signals.A low-noise regulator chip using a linear regulator as a power module realizes low-noise power supply for the preamplifier circuit.The test and experimental results,the inductive magnetic sensor can replace the imported sensor for geophysical exploration when the measurement signal is strong.