| 摘要 |
An electromagnetic logging apparatus for investigating properties of an earth formation surrounding a borehole comprises an electromagnetic energy transmitter and four receivers supported by a support member, a measurement channel, and a multiplexer for selectively coupling the measurement channel to the receivers. The measurement channel comprises an amplitude processing channel including a highly gain-stabilized amplifier and gain control circuit; a phase processing channel including a highly phase-stabilized amplifier; and a circuit for measuring the amplitude and phase. The gain of the gain-stabilized amplifier is controlled by the gain control circuit in a closed loop feedback arrangement, while the gain of the phase-stabilized amplifier is controlled by the same gain control circuit without the closed loop arrangement. Phase is detected in the phase processing channel by a zero crossing detector and a mode detector, and is measured in the amplitude and phase measurement circuit by a rising edge detector, a falling edge detector, and means for determining a phase value. Amplitude is detected in the amplitude processing channel with an amplitude detector. A related electromagnetic logging method is disclosed.
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