Research On High Constant Current Source Circuit Of Electrode For Electrode Spectrum Logging

The traditional electrical logging method has less frequent measurements,single parameter.After the discovery of rock dielectric dispersion phenomenon,multi-frequency measurements can obtain the rich information of the rock.Based on the rock dispersion characteristics,the formation is measured by 1kHz-500 kHz,and the complex resistivity dispersion information at different frequencies is obtained.By using the Cole-Cole model,the parameters can be obtained and evaluated the stratum oil saturation evaluated.Compared to the traditional electrical logging method,the electric spectrum logging has an unique advantage in the effective identification of low resistance oil and gas reservoirs.During the "12th Five-Year Plan",the preliminary test data was obtained at the Longdong base,and the expected target was achieved.The reproducibility was good,but there were still some shortcomings.The output impedance of the constant current source circuit has some room for improvement.1kHz-500 kHz the range of gaining flatness has some room for improvement as well.The wire which is between the constant current source and the electrode produce self-inductance effect for the high frequency is not eliminated.In this paper,through the research and analysis of the constant current source of amplifier circuit,the digital gain control method is used to compensate the high frequency unevenness,and the influence of the self inductance is eliminated by using the series resonance theory.At last,the main source board and screen flow source board are produced.After test and verification,the constant current source's output impedance is up to 380k? under 1kHz signal,which can output 100 mA high current and gain flatness of 0.5dB or less under the range from 1kHz to 500 kHz.At the same time,it is proved that the idea of series resonance can eliminate the influence of wire self-inductance,but the method introduces the switch channel,which has more impact than that of the wire.Therefore,the elimination method is of little significance.In short,through the above measures,the performance of the constant current source circuit is improved.