| 摘要 |
An apparatus for measuring the bending on a drill bit operating down hole in a well may comprise at least three pockets circumferentially spaced equidistantly around the drill collar of the drill string to which the drill bit is attached. Four strain gauges are equidistantly circumferentially spaced around each of the pockets so as to form first and second sets of strain gauges. The strain gauges in the first set are connected into one Wheatstone bridge while the gauges in the second set are connected in a second bridge. Each of the strain gauges that are oriented similarly within each of the pockets are connected in series within a single leg of a bridge so that the output voltage of the bridge is unaffected by bending in the drill string. The output of first bridge is used to determine the bending on the drill bit. Further, an apparatus for measuring the bending, weight, and torque on a drill bit operating down hole in a well may comprise at least three pockets circumferentially spaced equidistantly around the drill collar of the drill string to which the drill bit is attached with twelve strain gauges that are equidistantly circumferentially spaced around each of the pockets so as to form first and second sets of strain gauges. The arrangement of the twelve strain gauges allow for a bending on bit measurement that cancels out the affects of the weight on bit and torque on bit.
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