The Hardware Design Of The Medium Power Electrical Property Electromagnetic Transmitter

Borehole-ground electromagnetic method is a kind of electrical method in which the electricity is emitted under the borehole and the emitted signal is received on the ground. The source of the exciting field is placed in the borehole, so the emittion consequence of the source could be described as the most direct and effective one. Compared with the tradition electromagnetic method, borehole-ground electromagnetic method is able to make the wage of detecting much wider and the accuracy much higher.The experiment system of physical simulation of borehole-ground electromagnetic method consist of emission coefficient, receiving system and process of recorded data. Emission coefficient also can be divided into four parts—direct current source, medium power electrical property electromagnetic transmitter, transmitter cable and emitting eletrode. Then the key point must be the medium power electrical property electromagnetic transmitter whose performance determines the accuracy of emission coefficient and makes great effect on the laboratory findings further. After the direct current source emit current, the direct current will be inversed to multisystem rectangular pulse of single frequency or multi-frequency inside the the medium power electrical property electromagnetic transmitter. And then the electromagnetic signal is transmitted into the water tank via the transmitter cable and the emitting eletrode. In order to meet the demands of the experiment, the index of the transmitter are listed as follow:Transmitter current:10mA-5A;Transmitter voltage:0.5V-500V(direct or alternative current, maxvalue);Transimitter waveform:square wave with the duty ratio of 50% or 100%;Transmitter dominant frequency:1/128Hz~16384Hz , increased by2n(n=-10,-9,…,-1,0,1,…,14);Frequency stability:higher than±1.5×10-6;Lifetime : unless 4 hours;Adaping to fieldwork and laborary simuliting experiments;According the index before, IPM was chosen as the main inversion component, while ARM7 was used as the main controller which make a sequential circuit with CPLD. The collecting of asistant information resorts to the high speed working AVR. The lower power-expending ARM7 contains a 32-bit RISC processor, and its inner core performs as a triple strealine and belongs to Von Neuman architecture. So it can meet many performance requirements. Most of the AVR commands are period commands. AVR has a great series of registers and other well peripheral equipment. Thus the good performance of AVR also should not be ignored. IPM is such a quick switch, and low loss, reliable and easy to operate. The instrument which has been debugged and tested for many times prove to be qualified. The test items are composed of current, voltage, frequency and response to fault.