| 摘要 |
An improved apparatus is disclosed for use in a measuring while drilling apparatus which forms a pressure pulse promulgated from a downhole location upwardly through the drill string and column of mud therein. This apparatus includes a mud line section adapted to flow drilling mud in the mud flow line through an axial passage therein. The apparatus includes an encircling bladder which receives hydraulic oil under pressure to inflate to choke the passage. A Pitot tube is focused downstream and thus does not intercept the mud flow from the pump and the noise which is created by pump operation. Mud pressure variations directed upstream from the measuring while drilling apparatus, however, are directed into the Pitot tube. These pressure variations are coupled to a pressure signal transducer which forms an output signal of some type which is recorded. Pump noise is nulled to a minimum.
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