Importance

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Abstract

This invention is concerned with downhole measurements while drilling a borehole in the earth with a drill bit at the lower end of the drill string and transmitting such measurements to the surface. The drilling fluid is forced through a fluid passage which includes a drill string, a bit at the lower end thereof and the annulus surrounding the drill string. There is a restriction in the passage causing a pressure drop creating a high pressure zone and a low pressure zone within said passage, and a drilling fluid bypass comprising a bypass valve provides fluid communication between the high pressure zone and the low pressure zone. By means of a downhole sensor and associated equipment a plurality of pulse or electrical voltage change signals representing downhole information is produced. Each of these signals is arranged to generate several electrical voltage changes. A control means is provided to cause opening of the bypass valve responsive to one of these signals and for causing closing of the valve responsive to another of said signals.

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First Claim