Electromagnetic log

Claim 1

AN APPARATUS FOR MEASURING A SHIP''S VELOCITY AND DISTANCE THROUGH WATER COMPRISING A STREAMLINED STRUT SUPPORTED FROM SAID SHIP IN A REGION OF RELATIVELY UNDISTURBED WATER FLOW; A LONGITUDINAL MAGNETIC CORE AND COIL MOUNTED WITHIN SAID STRUT FOR SETTING UP IN ALTERNATING MAGNETIC FIELD PERPENDICULAR TO THE DIRECTION OF MOTION OF SAID SHIP; ELECTRODES SYMMETRICALLY POSITIONED ON SAID STRUT WITH RESPECT TO SAID CORE IN A REGION WHERE THE MAGNETIC FIELD IS SUBSTANTIALLY PARALLEL TO SAID STRUT FOR DETECTING VOLTAGES INDUCED IN THE WATER DUE TO THE MOTION OF SAID MAGNETIC FIELD THROUGH THE WATER; A POWER SOURCE FOR ELECTRICALLY ENERGIZING SAID COIL AND CORE; A POTENTIOMETER CONNECTED IN SERIES WITH SAID POWER SOURCE AND COIL WHEREBY THE VOLTAGE ACROSS SAID POTENTIOMETER WILL BE IN PHASE WITH THE CURRENT THROUGH SAID COIL; AN AMPLIFIER HAVING AN INPUT CONNECTED TO SAID ELECTRODES AND AN OUTPUT; A PHASE SENSITIVE DETECTOR INCLUDING A RECTIFIER BRIDGE, RING MODULATOR HAVING ONE INPUT CONNECTED TO SAID AMPLIFIER OUTPUT, ANOTHER INPUT CONNECTED ACROSS SAID POTENTIOMETER WHEREBY SAID AMPLIFIER OUTPUT MAY BE DETECTED IN SAID MODULATOR BY SAID POTENTIOMETER VOLTAGE, AND AN OUTPUT; MEANS CONNECTED TO THE OUTPUT OF SAID DETECTOR FOR SELECTING AN ADJUSTABLE VOLTAGE FROM SAID POTENTIOMETER AND APPLYING SAID ADJUSTABLE VOLTAGE TO SAID AMPLIFIER INPUT IN PHASE OPPOSITION TO SAID INDUCED VOLTAGES, WHEREBY SAID INDUCED VOLTAGES ARE SUBSTANTIALLY CANCELLED; AND A SPEED INDICATOR AND AN INTEGRATING COUNTER FOR INDICATING DISTANCE TRAVELED CONNECTED TO AND OPERATED BY SAID LAST NAMED MEANS.

Claim 2

AN APPARATUS FOR MEASURING A SHIP''S VELOCITY AND DISTANCE THROUGH WATER COMPRISING A STREAMLINED STRUT SUPPORTED FROM SAID SHIP IN A REGION OF RELATIVELY UNDISTURBED WATER FLOW; A LONGITUDINAL MAGNETIC CORE AND COIL MOUNTED WITHIN SAID STRUT FOR SETTING UP IN ALTERNATING MAGNETIC FIELD PERPENDICULAR TO THE DIRECTION OF MOTION OF SAID SHIP; ELECTRODES SYMMETRICALLY POSITIONED ON SAID STRUT WITH RESPECT TO SAID CORE IN A REGION WHERE THE MAGNETIC FIELD IS SUBSTANTIALLY PARALLEL TO SAID STRUT FOR DETECTING VOLTAGES INDUCED IN THE WATER DUE TO THE MOTION OF SAID MAGNETIC FIELD THROUGH THE WATER; A POWER SOURCE FOR ELECTRICALLY ENERGIZING SAID COIL AND CORE; A POTENTIOMETER CONNECTED IN SERIES WITH SAID POWER SOURCE AND COIL WHEREBY THE VOLTAGE ACROSS SAID POTENTIOMETER WILL BE IN PHASE WITH THE CURRENT THROUGH SAID COIL; AN AMPLIFIER HAVING AN INPUT CONNECTED TO SAID ELECTRODES AND AN OUTPUT; A PHASE SENSITIVE DETECTOR INCLUDING A RECTIFIER BRIDGE, RING MODULATOR HAVING ONE INPUT CONNECTED TO SAID AMPLIFIER OUTPUT, ANOTHER INPUT CONNECTED ACROSS SAID POTENTIOMETER WHEREBY SAID AMPLIFIER OUTPUT MAY BE DETECTED IN SAID MODULATOR BY SAID POTENTIOMETER VOLTAGE, AND AN OUTPUT; MEANS CONNECTED TO THE OUTPUT OF SAID DETECTOR FOR SELECTING AN ADJUSTABLE VOLTAGE FROM SAID POTENTIOMETER AND APPLYING SAID ADJUSTABLE VOLTAGE TO SAID AMPLIFIER INPUT IN PHASE OPPOSITION TO SAID INDUCED VOLTAGES, WHEREBY SAID INDUCED VOLTAGES ARE SUBSTANTIALLY CANCELLED; AND A SPEED INDICATOR AND AN INTEGRATING COUNTER FOR INDICATING DISTANCE TRAVELED CONNECTED TO AND OPERATED BY SAID LAST NAMED MEANS.