Broadband Analysis of Response From Magnetic Cores Used in Inductive Sensors for Pulsed Nuclear Magnetic Resonance Applications

Inductive sensors used in oil-field well-logging instruments can detect the presence of oil/water in earth formations. The inductive sensor acts as both a signal transmitter and receiver and, at the same time, contributes its own intrinsic signal to each measurement. Often, this contribution can mask the actual measured signal. It is thus vital to reduce the contribution of the inductive sensor signal from the measured signal. Since the major contributor to the signal from the inductive sensor is the magnetic core, the focus of this paper is to identify its signal characteristics and minimize the interference due to the magnetic core material. On the basis of a signal analysis, Mu 125 is identified as a suitable core material for inductive sensors due to its lower signal amplitude and shorter decay time at each resonant frequency.