| 摘要 |
<p>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 gainstabilized amplifier is controlled by the gain control circuit in a closed loop feedback arrangement, while the gain of the phasestabilized 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.</p> |
