# US 4,395,908 A · Means for adjusting the sensitivity of a crystal detector

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- Number: US 4,395,908 A
- Document ID: US4395908A
- Status: Granted
- Kind: A
- Application number: 06/296,769
- Filed: 1981-08-27
- Granted: 1983-08-02
- Earliest claimed: 1981-08-27
- Assignees: Western Geophysical Company of America
- Inventors: Robert C. Shopland
- Web page: https://patentgrep.com/patent/US4395908A

## CPC

- B06B 1/0666: {used as a diaphragm}
- G01P 15/09: by piezoelectric pick-up
- B06B: METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, {e.g.} FOR PERFORMING MECHANICAL WORK IN GENERAL (for particular applications, see the relevant subclasses, e.g. B07B1/40, B23Q17/12, B24B31/06; measurement of mechanical vibrations G01H; in direction finding, locating, distance or velocity measuring G01S; {generating seismic energy G01V1/02}; control of mechanical vibrations in general G05D; sound-producing devices, e.g. bells, sirens, whistles G10K, {e.g. methods or devices for transmitting, conducting, or directing sound in general G10K11/00}; generation of electrical oscillations H03B; electromechanical resonators in general H03H; electromechanical transducers {for communication techniques, e.g. microphones, speakers} H04R)
- 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})

## Abstract

A twin-transducer seismic detector includes a hollow housing closed at each end by a diaphragm-type transducer. A deformable retaining member is pressed against the perimeter of each transducer. An adjustable force is applied to at least one of the deformable members to cause the member to flatten against the transducer. As the deformable member becomes flattened, it reduces the effective area of the transducer and hence alters its compliance and sensitivity. The applied force is adjusted so as to match the sensitivity of one transducer to that of the other transducer.

## Claims

### Claim 1

In a detector of the type including a housing having an internal chamber that is closed at each end by a diaphragm-type transducer, means for matching the sensitivity of said transducers, comprising:
a shoulder at each of said housing for receiving each said transducer;
resilient deformable members contacting said transducers externally of said chamber;
means for urging said resilient deformable members against said transducers; and
means for applying an adjustable deforming force to at least one of said deformable members through said urging means to alter the compliance of the corresponding transducer until its sensitivity matches the sensitivity of the other transducer.

### Claim 2 (depends on 1)

The transducer sensitivity-matching means as defined by claim 1, comprising:
threaded, rotatable end caps, mating with corresponding threads in the ends of said housing for applying said deforming force to said urging means and thence to said deformable members.

### Claim 3 (depends on 1)

The transducer sensitivity-matching means as defined in claim 1 wherein said deformable members flatten against said transducers and spread under the pressure of a deforming force thereby altering the compliance of said transducers.

### Claim 4 (depends on 1)

The transducer sensitivity-matching means as defined in claim 1 wherein increased deforming forces flatten and spread said deformable members against said transducers to reduce the area of said transducers thereby to reduce the sensitivity thereof.

### Claim 5

In an accelerometer of the type including a housing closed at each end by a diaphragm-type transducer to form a chamber for containing a volume of a liquid inertia mass internally of said housing between said transducers, the improvement comprising:
resilient deformable ring members contacting said transducers around the perimeters thereof, externally of said chamber;
bezel rings for urging said deformable ring members against said transducers;
threaded, rotatable end caps for pressing said bezel rings against said deformable ring members to apply an adjustable deforming force to said ring members so that they spread out to alter the compliance of said transducers.

### Claim 6 (depends on 5)

The improved accelerometer as defined in claim 5, comprising:
micrometric indications on at least one of said end caps to provide means for quantitative measure of said tensioning force.