Time variable gating for acoustic logging

Claim 1

A SYSTEM FOR MEASURING THE ACOUSTIC VELOCITY OF FORMATIONS ADJACENT A WELL BORE THAT COMPRISES AN ACOUSTIC PULSE TRANSMITTER MOVABLY POSITIONED IN SAID WELL BORE FOR PERIODICALLY GENERATING AND TRANSMITTING TO SAID FORMATION AN ACOUSTIC PULSE, MEANS FOR GENERATING A CONTROL PULSE IN TIME COINCIDENCE WITH THE GENERATION OF SAID ACOUSTIC PULSE, A VOLTAGE GENERATOR FOR GENERATING A VOLTAGE THAT INCREASES MONOTONICALLY AS A FUNCTION OF TIME, SAID LASTNAMED MEANS BEING CONNECTED TO SAID VOLTAGE GENERATOR SO THAT SAID VOLTAGE IS PRODUCED RESPONSIVE TO SAID CONTROL PULSE, A CAPACITOR, A NORMALLY OPEN SWITCH CONNECTING SAID CAPACITOR TO SAID VOLTAGE GENERATOR, AN ACOUSTIC RECEIVER MOVABLY POSITIONED IN SAID WELL BORE IN PREDETERMINED SPACED APART RELATIONSHIP WITH SAID ACOUSTIC TRANSMITTER FOR PRODUCING AN ELECTRICAL SIGNAL RESPONSIVE TO THE APPEARANCE OF SAID ACOUSTIC PULSE, CONTROL CIRCUIT MEANS FOR MOMENTARILY CLOSING SAID SWITCH RESPONSIVE TO SAID ELECTRICAL SIGNAL, A NORMALLY CLOSED GATING AMPLIFIER CONNECTING SAID ACOUSTIC RECEIVER TO SAID CONTROL CIRCUIT MEANS, MEANS RESPONSIVE TO THE PRESENCE OF SAID CONTROL PULSE FOR ACTUATING SAID VOLTAGE GENERATOR, SAID LAST-NAMED MEANS BEING CONNECTED TO SAID NORMALLY CLOSED GATING AMPLIFIER FOR OPENING SAID NORMALLY CLOSED GATING AMPLIFIER, AND MEANS BIASED BY THE POTENTIAL TO WHICH SAID CAPACITOR IS CHARGED FOR GENERATING A SIGNAL EFFECTIVE TO DISABLE SAID NORMALLY CLOSED GATING AMPLIFIER FOR A TIME LESS THAN THE TIME INTERVAL REQUIRED FOR THE LAST PRECEDING ACOUSTIC PULSE TO TRAVEL FROM SAID ACOUSTIC PULSE TRANSMITTER TO SAID ACOUSTIC TRANSDUCER BY AN AMOUNT SUBSTANTIALLY EQUAL TO THE MAXIMUM EXPECTED CHANGE IN THE TIME INTERVAL OF SUCCESSIVE PULSES DUE TO CHANGE IN THE CHARACTERISTICS OF THE FORMATIONS TO BE LOGGED.

Claim 2

A SYSTEM FOR MEASURING THE ACOUSTIC VELOCITY OF FORMATIONS ADJACENT A WELL BORE THAT COMPRISES AN ACOUSTIC PULSE TRANSMITTER MOVABLY POSITIONED IN SAID WELL BORE FOR PERIODICALLY GENERATING AND TRANSMITTING TO SAID FORMATION AN ACOUSTIC PULSE, MEANS FOR GENERATING A CONTROL PULSE IN TIME COINCIDENCE WITH THE GENERATION OF SAID ACOUSTIC PULSE, A VOLTAGE GENERATOR FOR GENERATING A VOLTAGE THAT INCREASES MONOTONICALLY AS A FUNCTION OF TIME, SAID LASTNAMED MEANS BEING CONNECTED TO SAID VOLTAGE GENERATOR SO THAT SAID VOLTAGE IS PRODUCED RESPONSIVE TO SAID CONTROL PULSE, A CAPACITOR, A NORMALLY OPEN SWITCH CONNECTING SAID CAPACITOR TO SAID VOLTAGE GENERATOR, AN ACOUSTIC RECEIVER MOVABLY POSITIONED IN SAID WELL BORE IN PREDETERMINED SPACED APART RELATIONSHIP WITH SAID ACOUSTIC TRANSMITTER FOR PRODUCING AN ELECTRICAL SIGNAL RESPONSIVE TO THE APPEARANCE OF SAID ACOUSTIC PULSE, CONTROL CIRCUIT MEANS FOR MOMENTARILY CLOSING SAID SWITCH RESPONSIVE TO SAID ELECTRICAL SIGNAL, A NORMALLY CLOSED GATING AMPLIFIER CONNECTING SAID ACOUSTIC RECEIVER TO SAID CONTROL CIRCUIT MEANS, MEANS RESPONSIVE TO THE PRESENCE OF SAID CONTROL PULSE FOR ACTUATING SAID VOLTAGE GENERATOR, SAID LAST-NAMED MEANS BEING CONNECTED TO SAID NORMALLY CLOSED GATING AMPLIFIER FOR OPENING SAID NORMALLY CLOSED GATING AMPLIFIER, AND MEANS BIASED BY THE POTENTIAL TO WHICH SAID CAPACITOR IS CHARGED FOR GENERATING A SIGNAL EFFECTIVE TO DISABLE SAID NORMALLY CLOSED GATING AMPLIFIER FOR A TIME LESS THAN THE TIME INTERVAL REQUIRED FOR THE LAST PRECEDING ACOUSTIC PULSE TO TRAVEL FROM SAID ACOUSTIC PULSE TRANSMITTER TO SAID ACOUSTIC TRANSDUCER BY AN AMOUNT SUBSTANTIALLY EQUAL TO THE MAXIMUM EXPECTED CHANGE IN THE TIME INTERVAL OF SUCCESSIVE PULSES DUE TO CHANGE IN THE CHARACTERISTICS OF THE FORMATIONS TO BE LOGGED.