Position locating using digital logic controlled by pulse propagation time intervals

Apparatus for measuring required time for a wave energy impulse to propagate from end to end of an elongated propagative member utilizing a wave energy impulse induced in the member for bi-directional propagation therein at an undetermined energizing location intermediate such ends, wherein the member is terminated at one end to reflect incident wave energy therein without phase reversal and at its opposite end to reflect incident wave energy with phase reversal, transducer means in energy transfer relationship with said member responsive to a change in the energy state of the member produced by traversal of said transducer means by propagating wave energy impulse, said transducer means being located adjacent to and spaced from said opposite end by a distance producing additive overlapping responses therein from incident and reflected waves traversing said transducer means providing a composite single response at substantially the instant the propagating impulse arrives at said opposite end, and time interval measurement means responsively connected to said transducer means for converting into said required time, occurrences of the latter's composite responses first from the wave energy impulse propagating to the transducer means directly from said energizing location and second from that propogating to said transducer means after reflection from said one end of the member, said measurement means including an input circuit that converts the respective transducer means composite responses each into first and second substantially squared waves, and wherein the time interval measurement means sums the following time intervals:

• the full interval between wave energy impulse induction and the first squared wave, three-fourths the time duration of the first squared wave, half the interval between termination of the first squared wave and inception of the second squared wave, and one-fourth the duration of the second squared wave.

Apparatus for sensing variations in required time for a wave energy impulse to propagate from end to end of an elongated propagative member utilizing a wave energy impulse induced repeatedly in the member for bi-directional propagation therein at an undetermined energizing location intermediate such ends, wherein the member is terminated at one end to reflect incident wave energy therein without phase reversal and at its opposite end to reflect incident wave energy with phase reversal, transducer means in energy transfer relationship with said member responsive to a change in the energy state of the member produced by traversal of said transducer means by the propagating wave energy impulse, said transducer means being located adjacent to and spaced from said opposite end by a distance producing additive overlapping responses therein from incident and reflected waves traversing said transducer means providing a composite single response at substantially the instant the propagating impulse arrives at said opposite end, and time interval measurement means responsively connected to said transducer means for converting into said required time, occurrences of the latter's composite responses first from each wave energy impulse propagating to the transducer means directly from said energizing location and second from each propagating to said transducer means after reflection from said one end of the member, said measurement means including an input circuit that converts the respective transducer means composite responses each into first and second substantially squared waves, and wherein the time interval measurement means sums the following time intervals following each induced impulse:

• the full interval between wave energy impulse induction and the first squared wave, three-fourths the time duration of the first squared wave, half the interval between termination of the first squared wave and inception of the second squared wave, and one-fourth the duration of the second squared wave, and means comparing said sum with a reference value after each induced impulse to provide an output representing the difference therebetween.