# US 11,307,326 B2 · Calibration of combined acceleration and pressure sensors > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,307,326 B2 - Document ID: US11307326B2 - Status: Granted - Kind: B2 - Application number: 15/961,693 - Filed: 2018-04-24 - Published: 2018-11-08 - Granted: 2022-04-19 - Earliest claimed: 2017-05-03 - Assignees: PGS Geophysical AS - Applicants: PGS Geophysical AS - Inventors: Stig Rune Lennart Tenghamn; Frederick James Barr - Web page: https://patentgrep.com/patent/US11307326B2 ## CPC - G01V 13/00: Manufacturing, calibrating, cleaning, or repairing instruments or devices covered by groups G01V1/00 – G01V11/00 - G01H 11/08: using piezoelectric devices - G01L 23/10: by pressure-sensitive members of the piezoelectric type - G01L 27/005: {Apparatus for calibrating pressure sensors} - G01P 15/09: by piezoelectric pick-up - G01P 21/00: Testing or calibrating of apparatus or devices covered by the preceding groups - G01V 1/164: {Circuits therefore} - G01V 1/186: {Hydrophones} - H04R 1/02: Casings; Cabinets {; Supports therefor;} Mountings therein (H04R1/28 takes precedence {; attachments for microphones H04R1/08; mounting of transducers in earpieces H04R1/1075}) - H04R 1/42: Combinations of transducers with fluid-pressure or other non-electrical amplifying means - H04R 1/44: Special adaptations for subaqueous use, e.g. for hydrophone - H10N 30/302: {Sensors} - G01V 1/187: {Direction-sensitive hydrophones} - G01V 1/189: {Combinations of different types of receiving elements} - G01V 1/38: specially adapted for water-covered areas (G01V1/28 takes precedence) - G01V: GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS (means for indicating the location of accidentally buried, e.g. snow-buried, persons A63B29/02) - G01H: MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES - G01L: MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE (weighing G01G) - G01P: MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT (measuring or recording blood flow A61B5/02, A61B8/06; monitoring speed or deceleration of electrically-propelled vehicles B60L3/00; vehicle lighting systems adapted to indicate speed B60Q1/54; determining position or course in navigation, measuring ground distance in geodesy or surveying G01C; combined measuring devices for measuring two or more variables of movement G01C23/00; measuring velocity of sound G01H; measuring velocity of light G01J7/00; measuring direction or velocity of solid objects by reception or emission of radiowaves or other waves and based on propagation effects, e.g. Doppler effect, propagation time, direction of propagation, G01S; measuring speed of nuclear radiation G01T; measuring acceleration of gravity G01V; {measuring or recording the speed of trains B61L23/00; speed indicators incorporated in motor vehicles B60K35/00; measuring frequency or phase G01R; traffic control G08G}) - H04R: LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS (producing sounds with frequency not determined by supply frequency G10K) - H10N: ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR ## Abstract Techniques are disclosed relating to calibrating sensors configured to measure both pressure and acceleration. In various embodiments, a system detects a first voltage produce by a first piezoelectric material in a hydrophone when the hydrophone is exposed to an acceleration and detects a second voltage produced by a second piezoelectric material in the hydrophone when the hydrophone is exposed to the acceleration. The system, in some embodiments, compares the first voltage and the second voltage. Based on the comparing of the first and second voltages, in some embodiments, the system determines a resistance for a variable resistor coupled to one of the first and second piezoelectric materials. ## Claims ### Claim 1 A method, comprising: detecting a first voltage produced by a first piezoelectric material in a hydrophone when the hydrophone is exposed to an acceleration; detecting a second voltage produced by a second piezoelectric material in the hydrophone when the hydrophone is exposed to the acceleration; comparing the first voltage and the second voltage; based on the comparing, determining a resistance for a variable resistor coupled to one of the first and second piezoelectric materials, wherein the first piezoelectric material is coupled across the variable resistor and an in-series resistor included in a voltage divider circuit, wherein the voltage divider circuit is configured to adjust voltages produced by the first piezoelectric material; adjusting the variable resistor to have the determined resistance such that a first subsequent voltage produced by the first piezoelectric material is adjusted to match a second subsequent voltage produced by the second piezoelectric material when the hydrophone is exposed to a subsequent acceleration; and detecting a third voltage produced by a first differential amplifier coupled to the variable resistor and the in-series resistor. ### Claim 2 (depends on 1) The method of claim 1, further comprising: detecting the third voltage when the hydrophone is exposed to a pressure; detecting a fourth voltage produced by a second differential amplifier coupled to the hydrophone when the hydrophone is exposed to the pressure; comparing the third voltage and the fourth voltage; and based on the comparing of the third and fourth voltages, determining an adjustment for at least one of the first and second differential amplifiers. ### Claim 3 (depends on 1) The method of claim 1, wherein the hydrophone is one of a plurality of hydrophones included in a streamer to be towed behind a survey vessel. ### Claim 4 (depends on 2) The method of claim 2, wherein the adjustment is determined such that a third subsequent voltage produced by the first differential amplifier matches a fourth subsequent voltage produced by the second differential amplifier when the hydrophone is exposed to a subsequent pressure. ### Claim 5 (depends on 2) The method of claim 2, wherein the first and second differential amplifiers are coupled to a plurality of other hydrophones that have respective first and second piezoelectric materials, wherein the first differential amplifier is coupled to ones of the respective first piezoelectric materials and the second differential amplifier is coupled to ones of the respective second piezoelectric materials. ### Claim 6 A method, comprising: detecting first and second voltages resulting respectively from first and second piezoelectric sensors being subject to an acceleration; comparing the first voltage and the second voltage; based on the comparing, determining an adjustment for a voltage divider coupled to one of the first and second piezoelectric sensors such that the voltage divider causes voltages produced respectively by the first and second piezoelectric sensors to match when the first and second piezoelectric sensors are subjected to the acceleration, wherein the adjustment for the voltage divider modifies a resistance of a variable resistor included in the voltage divide, wherein the first piezoelectric sensor is coupled across the variable resistor and an in-series resistor included in the voltage divider; and detecting a third voltage produced by a first differential amplifier coupled to the variable resistor and the in-series resistor. ### Claim 7 (depends on 6) The method of claim 6, further comprising: detecting third and fourth voltages resulting respectively from the first and second piezoelectric sensors being subjected to a pressure; comparing the third voltage and the fourth voltage; and based on the comparing of the third and fourth voltages, determining an adjustment for the first differential amplifier such that the first differential amplifier causes voltages produced respectively by the first and second piezoelectric sensors to match when the first and second piezoelectric sensors are subjected to the pressure. ### Claim 8 (depends on 6) The method of claim 6, wherein the first and second piezoelectric sensors are included in geophysical equipment to be towed by a survey vessel. ### Claim 9 (depends on 6) The method of claim 6, wherein the voltage divider is coupled to the first piezoelectric sensor via a first wire coupled to a housing structure associated with the first piezoelectric sensor and a second wire coupled to the first piezoelectric sensor. ### Claim 10 (depends on 7) The method of claim 7, wherein a second differential amplifier is coupled to the second piezoelectric sensor, wherein a difference between voltages resulting respectively from the first and second differential amplifiers is indicative of a particular acceleration experienced by the first and second piezoelectric sensors. ### Claim 11 (depends on 10) The method of claim 10, wherein an addition of the voltages resulting respectively from the first and second differential amplifiers is indicative of a particular pressure experienced by the first and second piezoelectric sensors. ### Claim 12 A method, comprising: subjecting first and second piezoelectric materials in a hydrophone to an acceleration without subjecting the first and second piezoelectric materials to a pressure, wherein the subjecting to the acceleration causes the first and second piezoelectric materials to produce a voltage signal representative of pressure; and adjusting a sensitivity to acceleration of at least one of the first and second piezoelectric materials such that the voltage signal representative of pressure is reduced, wherein the adjusting of the sensitivity to acceleration includes determining a resistance for a variable resistor in a voltage divider network such that the voltage divider network matches a sensitivity to acceleration of the first piezoelectric material with a sensitivity to acceleration of the second piezoelectric material; wherein the first piezoelectric material is coupled across the variable resistor and an in-series resistor included in the voltage divider network; and wherein a first differential amplifier is coupled to outputs of the variable resistor and the in-series resistor. ### Claim 13 (depends on 12) The method of claim 12, further comprising: subjecting the first and second piezoelectric materials to a pressure without subjecting the first and second piezoelectric materials to an acceleration, wherein the subjecting to the pressure causes the first and second piezoelectric materials to produce a voltage signal representative of acceleration; and adjusting a balance between the first differential amplifier and a second differential amplifier coupled to the first and second piezoelectric materials such that the voltage signal representative of acceleration is reduced. ### Claim 14 (depends on 12) The method of claim 12, wherein the adjusting of the sensitivity to acceleration includes determining an adjustment to a mass of the at least one piezoelectric material. ### Claim 15 (depends on 12) The method of claim 12, wherein the first and second piezoelectric materials are subjected to an acceleration using a shaker table. ### Claim 16 (depends on 12) The method of claim 12, wherein the hydrophone is one of a plurality of hydrophones included in a streamer to be towed behind a survey vessel.