The Design and Simulation of the Array Induction Logging Tools’ Signal Conditioning Circuit

Array induction logging tools (AILT) detects the stratum conductivity based on the principle of electromagnetic induction, as a result, the signal of the amplitude using the AILT is in microvolt level. The small-signal is always drowned by noise at high-temperature and high-pressure condition. In order to collect the weak signal accurately, we propose a design method of signal modulator circuits based on the principle of differential amplifier and active band-pass filter with second band limitless gain and multi-path negative feedback. First, make the induction signal obtained from the coil two stages amplification. Then Execute two-order band-pass filter to the enlarged signal. At last, process the filtered signal by the backward circuits. Simulating the circuits by Pspice16.3, The result of simulation indicated that the gain relative error of preamplifier is less than 1% and the center frequency relative error of band filter is less than 4%. These data suggest that the relative error of the design circuits is less than routine instrument by 5%. So the Simulation verifies the feasibility of the signal modulator circuit.