Key Technology Research Of Inductive Air-core Coil Sensor

TEM(transient electromagnetic method) has widely used in many aspects, such asmineral exploration, environmental surveys, oil and gas exploration, engineering exploration,archaeological exploration, military detection and so on, also achieved good results.According to the detection space classification, transient electromagnetic detection can bedivided into AEM, half AEM the ground transient electromagnetic method, mine and tunneltransient electromagnetic detection. Induction air-core coil sensor has been widely used intransient electromagnetic detection. It’s fit to receive transient electromagnetic signal for theinherent linear frequency characteristics and the advantages of non-core losses. Inductionair-core coil sensor is based on Faraday’s law of electromagnetic induction principle. After thetransmit current turned off, it will produce the secondary field, because of the eddy currenteffect of the geologic body. And thus a voltage is induced in the receiving coil, that is, thevoltage generated due to the change of the magnetic field, we can infer the distribution of theresistivity of the earth through the attenuation curve of the observed transient electromagneticsignal. At present, the domestic has not been mature commercialization of transientelectromagnetic sensor, most of the sensor is still dependent on imports. Therefore, thedevelopment of transient electromagnetic receiving sensor is particularly critical.In this paper, we study the basic principle of the induction air-core coil sensor, fordifferent application occasions, different types of receiving coil sensor are designed.Departure from the common principle of induction air-core coil sensor, this paper introducean important indicator of the sensor, analyzes the induction air-core coil’s sensitivity,signal-to-noise ratio and other indicators of the impact of factors. researches the frequencycharacteristic of the sensor under different damping coefficient, the impulse response and stepresponse, compares the output characteristic of the sensor under different damping casesthrough convolution computation, it comes to the conclusion that the sensor’s actual outputquickly converge with those of theoretical response under the condition of critical damping.Herein through the analysis the noise of the sensor, it obtains the background noise level. And starting from the key factors that affect sensor, it puts forward the plan of reducing thebackground noise of a sensor, including magnetic flux feedback scheme and cold resistance,their respective principle and the theory simulation results are given. Based on inductionair-core coil sensor system calibration method, This paper designs the calibration structure,using finite element software Ansoft Maxwell to simulate the various parts of theself-inductance and mutual inductance of the coil, and obtains the result of the comparison ofthe actual response and the coil sensor’s theory response.In order to verify the performance of the sensor, a set of field trials that are designed. Asto the portion of floor transient electromagnetic, it compared the Z component of the coil ofthe homemade induction air-core coil sensor and the3D-3coil of Canada’s Geonics Company,under the same measurement conditions, the measured decay curve is basically the same,andthe late noise is lower than the3D-3, based on the results of this comparison, field explorationtest in Inner Mongolia, the measurement results are consistent with the local geological data.As for half-airborne electromagnetic detecting section, firstly, measuring the noise level of thecoil sensor, and then using the manner of measuring the same region contrast with the groundsensor was tested, at last we got the consistent results. For the airborne electromagnetic part,compared the homemade aviation transient electromagnetic system with the CanadaAeroTEM system, consistent measurement results to verify the availability of the sensor.