| 摘要 |
An improved servo-driven pulser is disclosed, for use in measurement while drilling applications. In the pulser, a battery powered on-board DC electric motor is used to operate a servo-valve, which in turn adjusts internal tool fluid pressures to cause operation of a main valve to substantially reduce mud flow to a drill bit, thereby creating a positive pressure pulse detectable at the surface. De-energizing the motor driving the pilot valve results in re- adjustment of internal fluid pressures, causing the main valve to reopen, thereby terminating the pressure pulse.
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