Transmitter and receiver electrode method and apparatus for sensing presence and proximity of underwater obstructions

Claim 2

In an apparatus for sensing proximity of material obstructions in a fluid medium the combination of a pair of transmitter electrodes in spaced relation to each other in electrical engagement with the fluid medium, means for applying an electrical potential signal across said transmitter electrodes, at least one receiver electrode in electrical engagement with the fluid medium between and in spaced relation to the transmitter electrodes at a position along an imaginary line of symmetry through said transmitter electrodes closer to a center position between said transmitter electrodes than to either of said transmitter electrodes and spaced a substantial distance from said center position, carrier means rigidly fixing said electrodes in place for movement in said medium with said electrodes carried in the same relative positions with respect to each other, means coupled to said transmitter electrodes for deriving a reference potential, and electric signal measuring means coupled to the receiver electrode and reference means for measuring said signal at said receiver electrode with respect to said derived reference potential and including indicator means calibrated for sad signal measurement to indicate proximity of such obstruction beneath said electrodes.

Claim 3

The combination as in claim 1 wherein said fluid medium is water.

Claim 4

The combination as in claim 2 wherein said signal is an oscillatory signal.

Claim 5

The combination as in claim 3 wherein said measuring means includes a phase sensitive detector coupled for comparing said receiver electrode signal as appearing with respect to said reference potential to said oscillatory signal applied to the transmitter electrodes.

Claim 6

The combination as in claim 3 wherein a said reference means includes second receiver electrode fixed to said carrier means in electrical engagement with the water in line with the transmitter electrodes and displaced from said center position between said transmitter electrodes by the same distance as said first mentioned receiver electrode and on the opposite side of said center position from that of said first mentioned receiver electrode, said receiver electrodes being separated by a distance equal to about one-tenth to one-fifth the distance between said transmitter electrodes, and said reference means is couplet to both said receiver electrodes.

Claim 7

The combination as in claim 5 wherein said measuring means includes a signal balancing circuit coupled to said signal applying means and receiver electrodes for providing an electric bridge balance for said receiver electrode signal.

Claim 8

In an apparatus for sensing proximity of material obstructions in a fluid medium the combination of a pair of transmitter electrodes in spaced relation to each other and in electrical engagement with the fluid medium, means for applying an oscillatory electric potential signal across said transmitter electrodes, at least one pair of receiver electrodes in electrical engagement with the fluid medium on an imaginary receiver electrode line in tRansverse relation to an imaginary line of symmetry through said transmitter electrodes and on respective sides of said line of symmetry, said receiver electrode line being substantially closer to one of said transmitter electrodes than the other of said transmitter electrodes, carrier means rigidly fixing said electrodes in place for movement in said medium with said electrodes carried in the same relative positions with respect to each other, means coupled for measuring the signal across said receiver electrodes and including an indicator calibrated for said signal measurement to indicate the side proximate to a laterally disposed obstruction.

Claim 9

In an apparatus for sensing proximity of material obstructions in a fluid medium the combination of a pair of transmitter electrodes in spaced relation to each other and in electrical engagement with the fluid medium, means for applying an oscillatory electric potential signal across said transmitter electrodes, at least one pair of receiver electrodes in electrical engagement with the fluid medium on an imaginary receiver electrode line in tRansverse relation to an imaginary line of symmetry through said transmitter electrodes and on respective sides of said line of symmetry, said receiver electrode line being substantially closer to one of said transmitter electrodes than the other of said transmitter electrodes, carrier means rigidly fixing said electrodes in place for movement in said medium with said electrodes carried in the same relative positions with respect to each other, means coupled for measuring the signal across said receiver electrodes and including an indicator calibrated for said signal measurement to indicate the side proximate to a laterally disposed obstruction.

Claim 10

The combination as in claim 7 wherein said receiver electrode line is displaced from a center position between said transmitter electrodes by a distance equal to between one-fifth and one-tenth said transmitter electrode spacing.

Claim 11

The combination as in claim 7 wherein said receiver electrodes are separated by a distance equal to about one-tenth to one-fifth the distance between said transmitter electrodes and said imaginary receiver electrode line is displaced from a midpoint between said transmitter electrodes by a distance equal to about one-tenth to one-fifth the distance between said transmitter electrodes.

Claim 12

The combination as in claim 7 wherein said signal means includes a square wave oscillator; and said measuring means includes an amplifier coupled to said receiver electrodes, a phase sensitive detector coupled to said amplifier and oscillator for comparing said receiver electrodes and oscillator signals, indicator means coupled to said phase sensitive detector and calibrated for neutral indication when said transmitter electrodes are aligned with and in the center of a channel and for indication on respective sides of said neutral indication when said transmitter electrodes are displaced toward respective sides of said channel.

Claim 13

The combination as in claim 9 wherein said signal means includes a square wave oscillator; and said measuring means includes an amplifier coupled to said receiver electrodes, a phase sensitive detector coupled to said amplifier and oscillator for comparing said receiver electrodes and oscillator signals, indicator means coupled to said phase sensitive detector and calibrated for neutral indication when said transmitter electrodes are aligned with and in the center of a channel and for indication on respective sides of said neutral indication when said transmitter electrodes are displaced toward respective sides of said channel.

Claim 14

The combination as in claim 11 wherein said indicator means includes audio alarm signal means arranged for audio indication at selected indicator values on respective sides of said neutral indication.

Claim 15

In an apparatus for sensing material obstructions in a water medium the combination of a pair of transmitter electrodes in spaced relation to each other in electrical engagement with said medium; means for applying an oscillatory electrical potential signal across said transmitter electrodes; two receiver electrodes in line with said transmitter electrodes and in electrical engagement with said medium, each receiver electrode being displaced on a respective side form a center position between said transmitter electrodes with the distance between the receiver electrodes being between one-tenth and one-fifth said transmitter electrode spacing; and electric signal measuring means coupled to said receiver electrodes for measuring the signal at said receiver electrodes, said measuring means including a signal balancing circuit coupled to said signal applying means and receiver electrodes for providing an electric bridge balance for said receiver electrode signal, a third pair of electrodes with each fixed close to a corresponding one of said transmitter electrodes, a voltage divider resistor and potentiometer resistor coupled in parallel across said last mentioned electrodes, a centertap on the voltage divider resistor, an adjustable wiper on the poTentiometer resistor, and a balancing transformer having a primary coupled to said centertap and adjustable wiper, and a secondary coupled in series with one of said displaced receiver electrodes.

Claim 16

In an apparatus for sensing material obstructions in a water medium the combination of a pair of transmitter electrodes in spaced relation to each other in electrical engagement with said medium; means for applying an oscillatory electrical potential signal across said transmitter electrodes; two receiver electrodes in line with said transmitter electrodes and in electrical engagement with said medium, each receiver electrode being displaced on a respective side form a center position between said transmitter electrodes with the distance between the receiver electrodes being between one-tenth and one-fifth said transmitter electrode spacing; and electric signal measuring means coupled to said receiver electrodes for measuring the signal at said receiver electrodes, said measuring means including a signal balancing circuit coupled to said signal applying means and receiver electrodes for providing an electric bridge balance for said receiver electrode signal, a third pair of electrodes with each fixed close to a corresponding one of said transmitter electrodes, a voltage divider resistor and potentiometer resistor coupled in parallel across said last mentioned electrodes, a centertap on the voltage divider resistor, an adjustable wiper on the poTentiometer resistor, and a balancing transformer having a primary coupled to said centertap and adjustable wiper, and a secondary coupled in series with one of said displaced receiver electrodes.

Claim 17

The combination as in claim 13 wherein said measuring circuit has additionally means for amplifying said bridge balanced receiver electrode signal, and a phase sensitive detector coupled to said amplifier means and transmitter electrode signal applying means for comparing said amplified signal and transmitter means signal.

Claim 18

The combination as in claim 14 having additionally a pair of receiver channel follower electrodes in spaced relation to each other transversly to and on respective sides of said in line electrodes and displaced from said center position by a distance equal to one-fifth to one-tenth of the spaced relation of said transmitter electrodes, and means for coupling said channel follower receiver electrodes to said signal measuring means.

Claim 19

The combination as in claim 15 including additionally a boat having a bottom substantially symmetrical on either side of a center axis and said electrodes are fixed to electrically engage said water at said bottom with said transmitter and in line electrodes being on said axis.

Claim 20

In an apparatus for sensing material obstructions in a water medium the combination of a pair of transmitter electrodes in spaced relation to each other in electrical engagement with said medium; means for applying an oscillatory electrical potential signal across said transmitter electrodes; two receiver electrodes in spaced relation to each other, equally distant from a center position between said transmitter electrodes, in transverse relation to said transmitter electrodes and displaced from said center position by a distance equal to between one-fifth and one-tenth said transmitter electrode spacing; and electric signal measuring means coupled to said receiver electrodes for measuring the signal at said receiver electrodes, said measuring means including a channel follower transformer with a primary coupled across said receiver electrodes, a centertap on said primary, a reference signal source, and a depth finder transformer having a primary coupled to said centertap and reference signal source, thereby effecting across said channel follower transformer electric signals having an intensity correlation to orientation of said transmitter electrodes in a channel and across said depth finder transformer electric signals having an intensity correlation to depth of said medium.

Claim 21

In an apparatus for sensing material obstructions in a water medium the combination of a pair of transmitter electrodes in spaced relation to each other in electrical engagement with said medium; means for applying an oscillatory electrical potential signal across said transmitter electrodes; two receiver electrodes in spaced relation to each other, equally distant from a center position between said transmitter electrodes, in transverse relation to said transmitter electrodes and displaced from said center position by a distance equal to between one-fifth and one-tenth said transmitter electrode spacing; and electric signal measuring means coupled to said receiver electrodes for measuring the signal at said receiver electrodes, said measuring means including a channel follower transformer with a primary coupled across said receiver electrodes, a centertap on said primary, a reference signal source, and a depth finder transformer having a primary coupled to said centertap and reference signal source, thereby effecting across said channel follower transformer electric signals having an intensity correlation to orientation of said transmitter electrodes in a channel and across said depth finder transformer electric signals having an intensity correlation to depth of said medium.

Claim 24

The method as in claim 18 wherein said fourth small area position in said medium is spaced from the third position by a distance equal to about one-tenth to one-fifth the distance between the first mentioned two positions for providing said reference signal potential for the measurement of the resulting signal potential at the third position.

Claim 25

The method of sensing the presence and proximity of material obstruction in a fluid medium comprising tHe steps of applying an oscillatory electric potential to the fluid medium across two spaced apart small area positions in said medium, measuring the resulting signal potential at a third small area position in the medium with respect to a fourth small area position under conditions of known material obstruction within the useful measuring range, the third and fourth positions being along an imaginary line of symmetry through the first and second positions and spaced a substantial distance from a center point between said first and second positions, and indicating the amount of any change in the measured signal potential at the third position with respect to said fourth position under unknown material obstruction in the fluid medium in terms of proximity to such obstruction beneath said positions. 21.. The method as in claim 20 wherein the third and fourth positions are spaced by a distance equal to about one-tenth to one-fifth the distance between the first mentioned two positions.

Claim 26

In a ship mounted apparatus for sensing proximity of material underwater obstructions to movement of said ship through the water to facilitate guidance of said ship in manner to avoid contact with such obstructions, the combination of a pair of transmitter electrodes mounted on the hull of said ship in spaced relation to each other in electrical engagement with said water, means for applying an electrical potential signal across said transmitter electrodes, at least one receiver electrode mounted on the hull of said ship in electrical engagement with the water between and in spaced relation to the transmitter electrodes at a position which is on an imaginary line of symmetry through said transmitter electrodes and displaced from a center position between said transmitter electrodes by a substantial distance, means coupled to said transmitter electrodes for deriving a reference potential and electric signal measuring means coupled to said receiver electrode and reference means for measuring the signal at said receiver electrode with respect to said derived reference potential and including indicator means calibrated for said signal measurement to indicate proximity of such obstruction beneath said ship.

Claim 27

In a ship mounted apparatus for sensing proximity of material underwater obstructions to movement of said ship through the water to facilitate guidance of said ship in manner to avoid contact with such obstructions, the combination of a pair of transmitter electrodes mounted on the hull of said ship in spaced relation to each other in electrical engagement with said water, means for applying an electrical potential signal across said transmitter electrodes, at least one receiver electrode mounted on the hull of said ship in electrical engagement with the water between and in spaced relation to the transmitter electrodes at a position which is on an imaginary line of symmetry through said transmitter electrodes and displaced from a center position between said transmitter electrodes by a substantial distance, means coupled to said transmitter electrodes for deriving a reference potential and electric signal measuring means coupled to said receiver electrode and reference means for measuring the signal at said receiver electrode with respect to said derived reference potential and including indicator means calibrated for said signal measurement to indicate proximity of such obstruction beneath said ship.

Claim 28

The combination as in claim 22 wherein said electrodes are at the bottom of said ship.

Claim 29

The combinations in claim 23 wherein said measuring means includes an indicator calibrated for said signal measurements to indicate depth of water below the level of said ship.

Claim 30

The combination as in claim 23 wherein said transmitter electrodes are respectively fore and aft of said ship at a centerline of said hull.

Claim 31

The combination as in claim 22 wherein said signal across said transmitter electrodes is an oscillatory signal, and said measuring means includes an amplifier coupled for amplifying said receiver electrode signal with respect to said reference potential, and a phase sensitive detector coupled for comparing said oscillatory signal to said amplified signal for improving the accuracy of said signal measurement on said indicator.

Claim 32

The combination as in claim 26 wherein said transmitting means includes a switching wave generator for effecting said oscillatory electrical potential signal.

Claim 33

In a ship mounted apparatus for sensing direction and proximity of massive underwater obstructions to movement of said ship through the water to facilitate guidance of said ship in manner to avoid contact with any of said obstructions, the combination of a pair of transmitter electrodes mounted fore and aft on the hull of said ship in spaced relation to each other in electrical engagement with said water, means for applying an electrical potential signal across said transmitter electrodes, a pair of receiver electrodes separate from said transmitter electrodes mounted in transverse relation to said transmitter electrodes on the hull of said ship in electrical engagement with the water and on respective sides of an imaginary line of symmetry through said transmitter electrodes, eacH of said receiver electrodes being substantially closer to one of said transmitter electrodes than the other of said transmitter electrodes and in spaced relation to the transmitter electrodes, and electric signal measuring means coupled to said receiver electrode pair for measuring the signal across said receiver electrodes, said measuring means including indicator means calibrated for indication of side and proximity of said ship to such massive barrier.

Claim 34

In a ship mounted apparatus for sensing direction and proximity of massive underwater obstructions to movement of said ship through the water to facilitate guidance of said ship in manner to avoid contact with any of said obstructions, the combination of a pair of transmitter electrodes mounted fore and aft on the hull of said ship in spaced relation to each other in electrical engagement with said water, means for applying an electrical potential signal across said transmitter electrodes, a pair of receiver electrodes separate from said transmitter electrodes mounted in transverse relation to said transmitter electrodes on the hull of said ship in electrical engagement with the water and on respective sides of an imaginary line of symmetry through said transmitter electrodes, eacH of said receiver electrodes being substantially closer to one of said transmitter electrodes than the other of said transmitter electrodes and in spaced relation to the transmitter electrodes, and electric signal measuring means coupled to said receiver electrode pair for measuring the signal across said receiver electrodes, said measuring means including indicator means calibrated for indication of side and proximity of said ship to such massive barrier.

Claim 35

The combination as in claim 28 wherein said electrodes are at the bottom of said hull with said transmitter electrodes being respectively fore and aft of said ship along a centerline of said hull, and said receiver electrodes are in transverse relation to said transmitter electrodes on respective sides of said centerline.

Claim 36

The combination as in claim 29 wherein said measuring means includes an indicator calibrated for a center of channel indication for massive channel barriers symmetrically located on respective sides of said ship and corresponding off center channel indication as said ship is disposed nearer to a corresponding one of said channel barriers.

Claim 37

The combination as in claim 30 wherein said electric signal potential across said transmitter electrodes is an oscillatory electrical signal potential, and said measuring means includes a differential amplifier coupled for amplifying the signal differential across said receiver electrode pair.

Claim 38

The combination as in claim 31 wherein said measuring means additionally includes a phase sensitive detector coupled for comparing said amplified signal from said amplifier and said oscillatory signal from said transmitter electrode applying means for improving accuracy of said receiver electrode signal measurement.

Claim 39

The combination as in claim 32 wherein said means for applying an electrical potential signal across said transmitter electrodes includes a switching wave generator for effecting said applied oscillatory electrical potential signal.

Claim 40

The combination as in claim 33 wherein said switching wave generator is a Royer oscillator.

Claim 41

The combination as in claim 31 having additionally means coupled to said transmitter electrodes for providing a reference potential signal; and said measuring means includes means for obtaining a receiver electrical potential signal intermediate the signal potentials between said pair of receiver electrodes, means for measuring said intermediate signal with respect to said reference, and an indicator calibrated for said measurement to indicate depth of water beneath said ship.

Claim 42

The combination as in claim 28 wherein a second pair of receiver electrodes are mounted on said hull in electrical engagement with the water and in parallel relation to said transmitter electrodes, and said measuring means includes an indicator calibrated for signal measurements across said second receiver electrode pair to indicate proximity of such obstructions disposed below the level of said ship.

Claim 43

The combination as in claim 36 wherein said electrodes are at the bottom of said hull with said pair of transmitter electrodes and said second receiver electrode pair being along a centerline of said hull.

Claim 44

The combination as in claim 37 wherein said electric signal potential across said transmitter electrodes is an oscillatory electrical signal potential, and said measuring means has additionally means coupled to said transmitter and receiver electrodes for modifying the electrical signal potential across said receiver electrode pair to facilitate correlation of said receiver electrode signals for said indication of proximity of such obstructions.

Claim 45

The combination as in claim 38 having additionally another pair of receiver electrodes at the bottom of said hull in transverse relation to said transmitter electrodes and an indicator arranged for operation with said transverse electrodes and calibrated for causing the signal across said pair of transverse electrodes to indicate proximity of such obstruction in lateRal relation to said ship.

Claim 46

In a ship mounted apparatus for indicating ship travel direction for optimum underwater channel clearance for said ship when in a water containing channel having sides forming massive barriers to movement of said ship in the direction of either of said sides, the combination of means on said ship including spaced apart forward and rearward transmitter positions for transmitting electric current through the water between the ship and each of the channel sides, means on said ship for measuring the potential difference between at least two positions in spaced relation to each other with each of said measuring positions being in the path of said current flow in said water at a corresponding one of said sides, said measuring positions being substantially closer to one of said forward and rearward transmitter positions than to the other of said forward and rearward transmitter positions and in transverse relation to said transmitter positions and indicator means coupled to said measuring means, said indicator means indicating said measurement in terms of said travel direction for optimum underwater channel clearance for said ship.

Claim 47

In a ship mounted apparatus for indicating ship travel direction for optimum underwater channel clearance for said ship when in a water containing channel having sides forming massive barriers to movement of said ship in the direction of either of said sides, the combination of means on said ship including spaced apart forward and rearward transmitter positions for transmitting electric current through the water between the ship and each of the channel sides, means on said ship for measuring the potential difference between at least two positions in spaced relation to each other with each of said measuring positions being in the path of said current flow in said water at a corresponding one of said sides, said measuring positions being substantially closer to one of said forward and rearward transmitter positions than to the other of said forward and rearward transmitter positions and in transverse relation to said transmitter positions and indicator means coupled to said measuring means, said indicator means indicating said measurement in terms of said travel direction for optimum underwater channel clearance for said ship.

Claim 48

The combination as in claim 40 wherein said ship has an elongated hull for normal ship travel in the elongated direction of said hull, said current flow through the water is between at least on e pair of transmitter electrodes at said forward and rearward positions forming part of said transmitting means, said transmitter electrodes being in spaced relation to each other in said elongated direction and fixed to said hull for electrical engagement with said water, and said measuring means includes at least one pair of receiver electrodes with one of said receiver electrodes for electrical engagement with the water at one of said two positions and the other of said receiver electrodes for electrical engagement with the water at one of said two positions and the other of said receiver electrodes for electrical engagement with the water at the other of said two positions.

Claim 49

The combination as in claim 41 wherein said hull is substantially symmetrical on each side of an imaginary centerline running longitudinally at the bottom of said hull, said transmitter electrodes are fixed to said hull in said forward and rearward positions for substantially symmetrical current conduction through said water on respective sides of said centerline when said water is free of obstructions, and said receiver electrodes are fixed to said hull below the water level on respective sides of said centerline.

Claim 50

The combination as in claim 42 wherein said current flow is oscillatory current flow from and alternating wave generating means which is coupled across said transmitter electrodes and forms part of said transmitting means, and said measuring means includes an amplifier and phase sensitive detector, the amplifier having an input coupled across said receiver electrodes and an output coupled to the phase sensitive detector for comparing the amplified potential difference from said receiver electrodes to a potential difference derived from the transmitting means current flow to improve accuracy of said measuring means.

Claim 51

The combination as in claim 43 wherein said pair of receiver electrodes are fixed in perpendicular relation to said transmitter electrodes for movement with said ship at all times in the same relative position with respect to each other and said ship hull.

Claim 52

In combination, a channel having longitudinally thereof sides forming massive barriers to movement of a ship in the direction of either of said sides, water in said channel, a ship in said channel floating in said water and having a hull with a longitudinal axis, transmitting means on said ship for transmitting electric current through said water about said ship from one position on said axis to another position on said axis, means on said ship for measuring the potential difference from said current flow at two positions in said water with each position bEing on a respective side of said axis and substantially closer to said one than said other transmitter positions on said axis, and indicator means coupled to said measuring means for indicating said measurement in terms of ship travel direction for optimum channel clearance for said ship.

Claim 53

In combination, a channel having longitudinally thereof sides forming massive barriers to movement of a ship in the direction of either of said sides, water in said channel, a ship in said channel floating in said water and having a hull with a longitudinal axis, transmitting means on said ship for transmitting electric current through said water about said ship from one position on said axis to another position on said axis, means on said ship for measuring the potential difference from said current flow at two positions in said water with each position bEing on a respective side of said axis and substantially closer to said one than said other transmitter positions on said axis, and indicator means coupled to said measuring means for indicating said measurement in terms of ship travel direction for optimum channel clearance for said ship.

Claim 54

In an apparatus for sensing material obstructions in a water medium the combination of a pair of transmitter electrodes in spaced relation to each other in electrical engagement with said water medium, means for applying an oscillatory electrical potential signal across said transmitter electrodes, at least one receiver electrode in electrical engagement with the water medium between and in line with the transmitter electrodes at a position which is displaced from a center position between said transmitter electrodes by a distance equal to between one fifth and one tenth said transmitter electrode spacing, carrier means rigidly fixing said electrodes in place for movement in said medium with said electrodes carried in the same relative positions with respect to each other, and electric signal measuring means coupled to the receiver electrode for measuring said signal at said receiver electrode, said measuring means including a circuit coupled to said transmitter electrodes for providing an electric reference signal for measurement of said receiver electrode signal, said last mentioned circuit including a pair of receiver electrodes with each of said pair fixed close to a corresponding one of said transmitter electrodes for providing the coupling thereto.

Claim 55

In an apparatus for sensing material obstructions in a water medium the combination of a pair of transmitter electrodes in spaced relation to each other in electrical engagement with said water medium, means for applying an oscillatory electrical potential signal across said transmitter electrodes, at least one receiver electrode in electrical engagement with the water medium between and in line with the transmitter electrodes at a position which is displaced from a center position between said transmitter electrodes by a distance equal to between one fifth and one tenth said transmitter electrode spacing, carrier means rigidly fixing said electrodes in place for movement in said medium with said electrodes carried in the same relative positions with respect to each other, and electric signal measuring means coupled to the receiver electrode for measuring said signal at said receiver electrode, said measuring means including a circuit coupled to said transmitter electrodes for providing an electric reference signal for measurement of said receiver electrode signal, said last mentioned circuit including a pair of receiver electrodes with each of said pair fixed close to a corresponding one of said transmitter electrodes for providing the coupling thereto.

Claim 56

In an apparatus for sensing material obstructions in a water medium the combination of a pair of transmitter electrodes in spaced relation to each other in electrical engagement with said water medium, means for applying an oscillatory electrical potential signal across said transmitter electrodes, a first receiver electrode in electrical engagement with the water medium between and in line with the transmitter electrodes at a position which is displaced from a center position between said transmitter electrodes, a second receiver electrode in electrical engagement with the water medium in line with the transmitter electrodes and displaced from said center position between said transmitter electrodes by the same distance as said first mentioned receiver electrode and on the opposite side of said center position from that of said first receiver electrode, said receiver electrodes being separated by a distance equal to about one tenth to one fifth the distance between said transmitter electrodes, and electric signal measuring means coupled to both said receiver electrodes, said measuring means including a signal balancing circuit coupled to said signal applying means and receiver electrodes for providing an electric bridge balance for said receiver electrode signal, said balancing circuit including a voltage divider resistor and potentiometer resistor, means coupling said voltage divider resistor and potentiometer resistor in parallel across said transmitter electrodes, a centertap on the voltage divider resistor, an adjustable wiper on the potentiometer resistor, a balancing transformer having a primary coupled to said centertap and adjustable wiper and a secondary coupled in series with one of said displaced receiver electrodes.

Claim 57

In an apparatus for sensing material obstructions in a water medium the combination of a pair of transmitter electrodes in spaced relation to each other in electrical engagement with said water medium, means for applying an oscillatory electrical potential signal across said transmitter electrodes, a first receiver electrode in electrical engagement with the water medium between and in line with the transmitter electrodes at a position which is displaced from a center position between said transmitter electrodes, a second receiver electrode in electrical engagement with the water medium in line with the transmitter electrodes and displaced from said center position between said transmitter electrodes by the same distance as said first mentioned receiver electrode and on the opposite side of said center position from that of said first receiver electrode, said receiver electrodes being separated by a distance equal to about one tenth to one fifth the distance between said transmitter electrodes, and electric signal measuring means coupled to both said receiver electrodes, said measuring means including a signal balancing circuit coupled to said signal applying means and receiver electrodes for providing an electric bridge balance for said receiver electrode signal, said balancing circuit including a voltage divider resistor and potentiometer resistor, means coupling said voltage divider resistor and potentiometer resistor in parallel across said transmitter electrodes, a centertap on the voltage divider resistor, an adjustable wiper on the potentiometer resistor, a balancing transformer having a primary coupled to said centertap and adjustable wiper and a secondary coupled in series with one of said displaced receiver electrodes.

Claim 58

In a ship mounted apparatus for sensing massive underwater obstructions to movement of said ship through the water to facilitate guidance of said ship in manner to avoid contact with any of said obstructions, the combination of a pair of transmitter electrodes mounted in spaced relation to each other fore and aft of said ship along a centerline of the hull at the bottom of said ship and in electrical engagement with said water, means for applying an oscillatory electrical signal potential across said transmitter electrodes, a pair of receiver electrodes separate from said transmitter electrodes mounted on the hull of said ship in transverse relation to said transmitter electrodes on respective sides oF said centerline, means coupled to said transmitter electrodes for providing a reference potential signal; and electric signal measuring means coupled to said receiver electrode pair for measuring the signal across said receiver electrodes, said measuring means including a differential amplifier coupled for amplifying the signal differential across said receiver electrode pair, an indicator calibrated for a center of channel indication for massive channel barriers symmetrically located on respective sides of said ship and corresponding off center channel indication as said ship is disposed nearer to a corresponding one of said channel barriers, means for obtaining a receiver electrical potential signal intermediate the signal potentials between said pair of receiver electrodes, means for measuring said intermediate signal with respect to said reference, and an indicator calibrated for said last mentioned measurement to indicate depth of water beneath said ship.

Claim 59

In a ship mounted apparatus for sensing massive underwater obstructions to movement of said ship through the water to facilitate guidance of said ship in manner to avoid contact with any of said obstructions, the combination of a pair of transmitter electrodes mounted in spaced relation to each other fore and aft of said ship along a centerline of the hull at the bottom of said ship and in electrical engagement with said water, means for applying an oscillatory electrical signal potential across said transmitter electrodes, a pair of receiver electrodes separate from said transmitter electrodes mounted on the hull of said ship in transverse relation to said transmitter electrodes on respective sides oF said centerline, means coupled to said transmitter electrodes for providing a reference potential signal; and electric signal measuring means coupled to said receiver electrode pair for measuring the signal across said receiver electrodes, said measuring means including a differential amplifier coupled for amplifying the signal differential across said receiver electrode pair, an indicator calibrated for a center of channel indication for massive channel barriers symmetrically located on respective sides of said ship and corresponding off center channel indication as said ship is disposed nearer to a corresponding one of said channel barriers, means for obtaining a receiver electrical potential signal intermediate the signal potentials between said pair of receiver electrodes, means for measuring said intermediate signal with respect to said reference, and an indicator calibrated for said last mentioned measurement to indicate depth of water beneath said ship.

Claim 60

In a ship mounted apparatus for sensing massive underwater obstructions to movement of said ship through the water to facilitate guidance of said ship in manner to avoid contact with any of said obstructions, the combination of a pair of transmitter electrodes mounted in spaced relation to each other along a centerline of the hull at the bottom of said ship and in electrical engagement with said water, means for applying an oscillatory electrical signal potential across said transmitter electrodes, a pair of receiver electrodes separate from said transmitter electrodes mounted at the bottom of said hull along said centerline in electrical engagement with the water and in spaced relation to said transmitter electrodes, and electric signal measuring means coupled to said receiver electrode pair for measuring the signal across said receiver electrodes, said measuring means including an indicator calibrated for said signal measurements across said receiver electrode pair to indicate proximity of such obstruction disposed below the level of said ship and means coupled to said transmitter and receiver electrodes for modifying the electrical signal potential from across said receiver electrode pair to facilitate correlation of said receiver electrode signals for said indication of proximity of such obstructions.

Claim 61

In a ship mounted apparatus for sensing massive underwater obstructions to movement of said ship through the water to facilitate guidance of said ship in manner to avoid contact with any of said obstructions, the combination of a pair of transmitter electrodes mounted in spaced relation to each other along a centerline of the hull at the bottom of said ship and in electrical engagement with said water, means for applying an oscillatory electrical signal potential across said transmitter electrodes, a pair of receiver electrodes separate from said transmitter electrodes mounted at the bottom of said hull along said centerline in electrical engagement with the water and in spaced relation to said transmitter electrodes, and electric signal measuring means coupled to said receiver electrode pair for measuring the signal across said receiver electrodes, said measuring means including an indicator calibrated for said signal measurements across said receiver electrode pair to indicate proximity of such obstruction disposed below the level of said ship and means coupled to said transmitter and receiver electrodes for modifying the electrical signal potential from across said receiver electrode pair to facilitate correlation of said receiver electrode signals for said indication of proximity of such obstructions.

Claim 62

The combination as in claim 49 wherein said measuring means includes a differential amplifier coupled to said receiver electrodes for amplifying said modified signal potential across said receiver electrode pair, and a phase sensitive detector coupled for comparing the amplified signal from said amplifier and said oscillatory signal from said applying means for improving accuracy of said receiver electrode signal measurement.