US1438974A - Piezo-electrical voltage indicator - Google Patents

Description

Dec. 19, 1922. 1,438,974. E. c. WENTE.

PIEZO-ELECTRICAL VOLTAGE INDICATOR. man Nov. x3, 1920.l

/nvenoh fdwdra 6. Wene 50 tals, such asi Patented Die. 1e, ieaa.

UNET@ STATES l,438,974 PATENT OFFICE.

EDWARD c. WDNTD, or NEW YORK, N. Y.,

ASSIGNOR TO WESTERN ELECTRIC COMPANY,

INCORPORATED, l02E* NEW YORK, N. Y., A CORPORATION OF NEW YORK.

PIEZO-EL'ECTRICAI'..` VOLTAG-E INDICATOR.

Application led November 13, 1920. erial Nc. 423,845.

To all lwhom it may concern:

Be it known that I, EDWARD C. WENTE, a citizen of the United States, residin at New York, in the .county of New ork,

5 State of New York, have invented certain new and useful Improvements in Piezo- Electrical Voltage Indicators, of which the following is a full, clear, concise, and Aexact description.y

Y This invention relates in general to electric current detecting devices and particu'- larly to such devicesfor use in connection with 'the recording of variations in voltage lntensity.

In apparatus heretofore vavailable for the analysls of complex sound waves, the analysis of vowel sounds has beenquite lsuccessfully, accomplished. For the analysis of consonant sounds however, it is essential 20 that the apparatus have little or no distortion for frequencies up to about 10,000 cycles per second. Considerable diiculty has heretofore been experienced in designing an oscillograph whichv has a` uniform characteristic. and is free from transient oscillations over this wide' range of frequencies. s y

The princip-al object of the present -in- Vention is to provide an instrument simple, accurate,'.positive in wave forms of alternating currents without distortion over a wide range of frequencies. 'A further object of the invention fis to provide a device with which may be used a larger reiector than is ordinarily possible,

so that when the device is used as an oscillograph Vibrator or similar apparatus the intensity of the focusing light will be greatly increased. 40v It has been found that in an ordinary oscillograph of the oil damped-type, dueto the change in the viscosity frequenc lcharacteristic 1s altered with changes 1n temperature. It is a further object of this invention to provide a' device for indicating the intensity of an electric current which will be unaffected by changes in atmospheric conditions.

It has been quartz are admirably adapted for. constructing vibrators 'having great stiffness. :From a considerationof .the f ollowing detaileddescription ojf-,the invention in its referredv form, taken in lconnection with t e accompanying drawings and-api action, for recording' vso-tightly as to inter of the oil, the" found that piezo-electric' crys 'wilLgve sufficient pended claims, further objects and features of the invention will be apparent.

Fig. l shows in perspective the invention as applied to an oscillograph system; and Fig. 2 is a longitudinal cross-sectional View -showing the electrical connections with the actuating elements.

Referring first to lFig. 1; 3 and 4 are two thin piezo-electric` crystal blades, such as quartz, of the same shape and size, rigidly fastened at one end in a moderately massive block 5; to the other end is attached an oscillograph mirror 6 of proper curvaturel The supporting block 5 must be of considerably greater mass than the mirror 6, in order to insure; against vibrations in the block instead of in the mirror. The quartz blades should be cut from the natural crystal in such la way that the greatest change in length is produced when a potential is ap. plied between the electrodes placed on their lateral faces. The method of cutting will of course vary with the type of piezo-electric crystal employed. Quartz, tourmalinev and Rochelle salts, for example, are all piezo-electrically active, but the method of cutting from the natural crystal may dlier in each case. The, electrodes shoul be so connected into the circuit that as one blade elongates, the other contracts; will then be rotated about its center of gravity. ,To prevent buckling, the quartz blades are held between metal slabs 7, which however, are not clam d against the quartz gere with thelr longitudinal movement. i

Inthe sectional view shown 1n Flg. 2. piezo-electrical blades `3 and 4 are securely held at one end in the block. The electrodes 9 andI 10 of metal foil are placed on the mirror 64 desired, be elec- The air'gaps between. the electrodes vand 10 and the metal small so that any ateral vibratlons o blades 3 and 4 are damped by the film of air. This ilm of air acts as `a cushlon and damping to minimize lateral motion.

.One met sound waves odfor the ,sis of com a .navidadA byynmkim @im lates- 7 are exceedm ly r as applied to the Rankine system for varyingthe intensity ofthe light falling on a photographic plate in accordance with a periodic stimulus: Thel light from the source 11 is brought to focus on the oscillograph mirror 6 by means of the lens 12. After reflection, it is again brought to focus on the photoraphic plate at 13 by means of the lens le.

n the plane surface 15 of the lens 12- 1s placed a grid consisting of opaque strips which are parallel to each other and yspaced so that the distances between the adjacent strips are the same and equal to the Width of the strips. On the plane surface 16 of the lens 14, an exactly similar grid is placed. If the miror 6 has the proper curvature and if the distances between/the lenses and the mirror are equal, an image of the grid at 15 of exactly the same size as the grid itself Will be formed on the plane surface 16. The image of .the grid at 15 may then be superimposed on the grid at 16. If the mirror 6 is in a position such that the image of the strips at 15 falls exactly on clear spaces of the grid at 16, no light will be transmitted to the point 13, Whereas a maximum amount of light Will be transmitted when the image of the strips atl15 lies exactly on the strips of the grid at 16. If the equilibrium point'A of the angular position at mirror 6 is properly adjusted, the light transmitted by thev system will be a linear function of the angulary displacement of the mirror about its equilibrium point. A photographic record may4 then be, obtained of the motion of the mirror 6, by moving the plate past the point 13.

With' a piezo-electric vibrator such as is describedin the present invention, a much larger mirror than can ordinarily be used in an oscillograph vibrator may be used, so that the intensity of the light reaching the film may be greatly increased;V This light may be focused directly on the photographic plate.

By means of this type of vibrator it is possible to record the Wave form of high frequency electric currents Without distortion.

If an oscillograph of this type is used with a condenser-transmitter and a distor-l ;ionless amplifier, la system can be so Vdesigned that there is practically no distor- ;ion over a Wide range of frequencies. It

vill thus be ,possible to obtain accurate .supporting said blades.

records of consonant sounds. Because ofA the importance of consonant sounds in speech transmission, this method will yield results of a greater value than have heretofore been obtainable.

- While the invention has beenA herein described yin its preferred form, it is noti intended to limit to the specific structure disclosed except Within the pended claims.

That is claimed is:

1.l In a device for indicating the intensity of an electric current, a plurality'of piezo.- electric crystalline blades rigidly supported Scope of the apat one end. a reflector supported by the free and means ends of said blades, for laterally 2. Ina device for indicatingthe intensity` of an electric current, a' plurality of piezo'- electric crystalline blades rigidly supported at one end, a reiector attached to the other movement of said blades to prevent them I from buckling when distorted.

4. In a device for* indicating the intensity of an electric current, a supporting member, a plurality o f piezo-electric crystalline blades supported at one ber, a member mechanically movable by said blades, and means for damping lateral movement of said blades comprising supporting mem-bers on the lateral faces thereof, but separated therefrom by an air gaP- 5. In a device'for'in-dicating the intensity of an electric current, a supporting member,

-a plurality of .piezo-electric crystalline blades supported at one end in sald mem. ber, electrodes disposed on the lateral faces' the end in. saidVV memof said4 blades, supporting members adjacent the lateral faces of said blades, but separated therefrom by air gaps, a reflector mounted on the free end'of said blades, and.

means for connectingsaid electrodes in an electric circuit. I

In witness whereof, I hereunto subscribe my name this 12th day 1920. il EDWARD C. WENTE..

ios

of November, D.,

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