A Novel Design of Master Control Syetem for Induced Polarization Logging Instrument

Describes the design and construction of a master control system for the induced polarization (IP) logging instrument that can directly work in oil well several kilometers away from the ground. By using the multi-channel conditioning circuits with different gains, the system has higher precision reaching 10 ppm under the wide dynamic range conditions. In addition, unlike the traditional instrument that uses single calibration signal, the present design uses multiple calibration signals to compute the gain of the amplification circuits with the curve fitting and least square method. This method can reduce the effects caused by temperature changes and chip variations. The core control system uses a digital signal processor (DSP) and a field-programmable gate-array (FPGA) to construct master-slave architecture. The FPGA is used to control logging work with powerful ability of parallel logic processing. On the other hand, the major works of DSP include communicating with host PC through the controller area network (CAN) bus, processing digital signal, and controlling FPGA. By experiments, this system can be operated stably under 150 centigrade.