| 摘要 |
A telemetry transmitter located in a portion of a drill string comprises an input for receiving and transmitting data obtained from at least one transducer arranged to sense a parameter of the drill string and/or a parameter of the surrounding medium. The transmitter comprises a magnetic dipole arranged to transmit an electromagnetic data signal, a current dipole arranged to transmit an electromagnetic data signal and control means for adaptively varying the power output from the magnetic and current dipoles, according to the orientation of the portion of the drill string containing the transmitter and according to the electrical resistivity of the medium surrounding the portion of the drill string containing the transmitter.
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