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Summary
Currently geophysical electromagnetic exploration for metal ores is facing some problems such as shallow probing depths, low accuracy and resolution, and poor anti-interference ability. To solve these difficulties, it is a feasible approach to make use of the existing mine tunnels, the electromagnetic transmitter on the ground and the recorders at the underground (borehole) or ground (prefecture) to compose a quasi-three-dimensional arrangement of measurement technology. This combination method of ground exciting and underground receiving can carry out observations from different directions to obtain subsurface electrical conductivity of the large amounts of information, and conduct quasi-three-dimensional imaging, allowing us to increase detection depth and resolution, and to reduce non-uniqueness in data interpretation and provide a new method for metallic ore exploration. The high-power single-frequency transmitter developed by our work can provide a single or multi-frequency inverter square wave, launching the signal frequency from DC to 9600Hz; the maximum emission voltage of 700V, and power supply current of 60A. This apparatus uses the GPS clock and real-time clock (RTC) module to ensure a regular and on time launching at scheduled frequencies. It can also make use of wireless Bluetooth and serial communication interface to control transmitting operation and edit the control parameter file and acquire a variety of supplementary status information. The experiment proves that the equipment is stable and reliable and can meet the requirements of conventional electromagnetic exploration and "tapping the deep and blind exploration of successive resources" for the exhausted mines.