Design And Implementation Of Three-component Transient Electromagnetic Receiving System

Transient electromagnetic method is a kind of artificial source time-domaingeophysical detection methods which is based on electromagnetic induction.Transient electromagnetic method (TEM) is regarded as an everlasting issue forgeological exploration. It is widely used in many research fields, such as mineralexploration, mineral exploration, tectonic sounding, environmental survey,archaeology and unexploded ordnance detection. The principle of transientelectromagnetic method is to establish a first pulse magnetic field undergroundthrough the ungrounded loop with pulse current. If the magnetic field encounters agood conductive geological body under the ground, it will produce eddy current in thegeological body. A new magnetic field can be further induced in the geological bodydue to the eddy current changing with times, which is called the secondary magneticfield. The receiver coil will couple with the secondary magnetic field. Through thelate inversion process, the signal of underground conductor can be obtained.At present, the study of transient electromagnetic detection system is mainlyconcentrated in the vertical component information acquisition and processing. But itis late for studying on acquisition and positive inversion of horizontal componentinformation, and there is no perfect detection system. The horizontal componentinformation includes rich information of the abnormal body. Comprehensive analysisthe horizontal and vertical components information can judge the position and shapeof the target body effectively, and can improve the interpretation precision. In order tosolve this problem，this paper introduced and designed the three-component transientelectromagnetic receiving system. We developed the three-component receivingsystem based on the working principle of the transient electromagnetic method, whichincluding design of three-component receiving coil, preamplifier and the receiving system. The receiving system is structured by LabVIEW and acquisition card, whichmainly completes the function of data acquisition. This paperachieves the background elimination, improves the noise level, and proposes thejudgment and revision algorithm of abnormal signal via MATLAB. Finally, the papershowed the test results of the calibration loop and the target body. The test resultsdemonstrated that the system can complete real-time data acquisition andpreprocessing, realize data playback and on-line analysis functions. Both movingmeasurement and base station measurement are available. The results alongthe survey lines are demonstrated in a two-dimensional figure. According tothe information of horizontal component and vertical component, the spatialdistribution of the target body can be determined. The results of this paper couldprovide theoretical guidance for further study of data inversion.