| 摘要 |
<p>A digital induction resistivity logging tool is disclosed for digitally measuring both the in-phase (R) and quadrature (X) phase components in a receiver signal generated in response to transmitter induced currents flowing in the earth's subsurface formations. The digital induction tool includes a digital sinewave generator for generating a highly phase stable, low distortion transmitter signal, the frequency of which is selectable from among a plurality of transmitter frequencies. One phase sensitive detector is used alternately to detect both the R and the X phase component signals. Automatic phase compensation is included to periodically compensate for both static and dynamic temperature dependent phase shift errors due to circuits of the tool involved in the component measurements. A floating point analog-to-digital converter capable of handling the wide dynamic range in the detected phase component signals is provided to convert the phase detector output into digital signals. Selection of the transmitter frequency may be based on optimizing the measurement of a characteristic of the formations being encountered by the tool. A linearization correction function is obtained periodically for the tool transfer function as the tool is being used in normal logging operations. The function is then applied to measurements taken subsequently.</p> |
