US783733A - Electrical measuring instrument. - Google Patents

Description

No. 783,783. PATENTED FEB.,28', 1905. W. A. PRICE.

ELECTRICAL MEASURING INSTRUMENT.

APPLICATION FILED FEB. 24. 1908.

2 SHEETS-SHEET 1 j 72 5 5141111586 58 /NV/V TOR MMW mm 102% No. 783,738. PATENTED FEB. 28, 1905. W. A. PRIGE. ELEGTEIGAL MEASURING INSTRUMENT.

APPLIUATION FILED FEB. 24. 1903.

2 SEEETS-BHEET 2.

No. 783,733. Patented February 28, I905.

NITED STATES PATENT I I ILEt WESTON A. PRICE, OF CLEVELAND, OHIO, ASSIGNOR TO THE ELECITRIC AND DENTAL SPECIALTY COMPANY, OF CLEVELAND, OIIIO, A COR- PORATION OF OHIO.

ELECTRICAL MEASURING INSTRUMENT.

SPECIFICATION forming part of Letters Patent No. 783,? 33, dated February 28, 1905.

Application filed February 24, 1903. Serial No. 144,611.

TO 10/7/07 1:15 {l thereon in a suitable manner a casing or cover Beitknown thatLW'ns'roNA.Paton,aciti- B, which incloses substantialLy all of the 5 zen of the United States, and a resident of mechanism embodied in the lllStlLllilUllC. in Cleveland, county of Cuyahoga, and State of the central portion of this base and intersect- Ohio, have invented a new and useful Iming the upper surface thereof is formed a deprovement in Electrical Measuring Instrupression (t for receiving the lower member of ments, of which the following is a specificaa sectional permanent magnet C, which is setion,the principle of the invention being herecured to the base by means of a plate c and a in explained and the best mode in which I screw 0. Two concave polc'picces c" c" are to have contemplated applying that principle, so secured upon the inner surface of the free as to distinguish it from other inventions. ends of the magnet, and upon the back of My invention relates to instruments for these polepieces is secured, by means of measuringelectricalcurrents,and particularly screws c, a su] )porting-piece 1;", formed with to milliammeters used in dental cataphorcsis. a lug c, projecting between the said two pole 5 The said inventionhas for its object the pro I pieces, as shown in Figs. I and II. To the vision of an ammeter of such delicacy of coni inner surface of said lug is secured, by means struction and operation as will permit elecof a screw 0, a soft-iron cylindrical core C, trical currents of exceedingly small amperage coaxial with the concave surface of the poleto effect a movement on the part of the indipieces. The upper base of such core is inter- 20 eating means connected therewith of comparasected by a centrally-located cylindrical bore tively large amplitude, so that readings of 0 from which projects a needle-point 0, fixed thousandths of milliamperes, hundredths of to the core, as shown in Fig. Ill. Upon this milliamperes, tenths of milliamperes, millineedle-point is supported an armature conamperes, as well as amperes, may be .made sisting of a coil I) of insulated wire wrapped 5 with facility and accuracy. upon a suitable frame (I. This frame has se' The said invention consists of means herecured to it and projecting from the under inafter fully described, and particularly set surface of its upper portion a centrally-loforth in the claims. cated bearing (Z, in which is journaled the The annexed drawings and the following deneedle-point. It will hence be seen that the 3 scription set forth in detail certain mechancoil is mounted to swing freely in suspenism embodying the invention, such disclosed sion in the annular space between the polemeans constituting but one of various mepieces and core, the needle -point forming 8O chanical forms in which the principle of the its sole support. Upon the upper surface of invention may be used. the pole-pieces are secured four headed pins 35 In said annexed drawings, Figure I repree a, two on each pole-piece, Fig. I. These sents a plan view of a Inilliammeter embody pins formabearing for an annular ring E, proing my invention, a part of the casing or vided with arearwardly-projectinghandpiece 5 cover being illustrated as broken away in ore, which projects through an aperture in the der to disclose the mechanism. Fig. II repcover B. This aperture is covered by a slid- 4- resents a vertical central longitudinal section ing plate 0, provided with an opening for perof said milliamrneter, parts out by the plane mitting the passage therethrough of the handof section being illustrated in elevation. Fig piece c, and is held in position by a helical 9 III represents a vertical transverse section spring 0", mounted upon such handpiecc intaken upon the plane indicated by the lines 3 termediately of said plate and the ring E, as

45 3 in Figs. I and II and viewed in the direcshown. Such plate in so closing such opention indicated by the arrows in said figures. ing permits of the partial rotation of the ring A base member A, preferably of wood or and at the same time prevents dust, Sac, from other non-conducting material, has secured entering the cover through opening 6. Upon this ring E is secured an upright curved stud a, to the upper end of which is secured the outer end of a spiral retractable spring a, the inner end of which is secured to an axial pintle (Z secured to the frame (Z, Fig. III. The pins (1 c are placed so as to exert an amount of frictional contact upon ring E, such as will prevent same from having its position unpremeditatedly altered after having been given a required position. The lower end of the frame is provided with a downwardly-projecting axial pintle to which is secured the inner end of a very sensitive spiral springe the outer end of which is secured to a clip f, secured to an insulated screw F, projecting from and secured to the one pole-piece of the magnet, as shown in Fig. III. Said spring a is of a trend opposite that of spring 6*, the relaxation being thereby neutralized, and serves to steady and balance the coil. One end of the latter is electrically connected with pintle (l and the other end with pintle cl", and the pole-pieces, ring E, stud c spring a, coil-pintle (Z coil-spring 6, clip f, and screw F are all connected electrically in series.

Two binding-posts G and H are provided and secured to the base A upon opposite sides of the cover B, as shown in Fig. I. Post Gr is connected by a wire conductor g (shown in dotted lines in Fig. I) with the plate 0. Post H is connected by a similar conductor it with the screw F. Post G is further connected by a second conductor g (shown in dotted lines in Fig. I) with one end of a series of conductors J J J J J of varying resistance. The other end of each such conductor is connected by means of separate conductors f, and with one of a series of plug-seats 1, 2, 8, 4t, and 5. A plug K is connected by means of a flexible conductor in with the binding-post H.

The front of the coverB is downwardly inclined and provided with an opening 6 covered with glass. Behind such opening is secured a scale M, suitably divided and marked.

Secured to the upper portion of the coilframe (Z is an indicating-pointer L, the point of attachment lying, as shown, substantially in the plane intersecting the plane of the needlepoint-that is, the point of support of the coil and parallel with the direction of movement of the coil. Upon the side of the upper frame portion opposite that to which the pointer is secured is an adjustable weight Z, counterbalancing the weight of the pointer.

The above-described construction, owing to the presence of a minimum amount of frictional resistance on the part of the means supporting the coil, is exceedingly sensitive to currents of extremely small amperage, so that a very considerable movement of the pointer is obtained by relatively small variations in the current passing through the coil.

In operation the terminals of the line are secured to the binding-posts G and H and the current passes through the conductor 9,

plate 0, magnet O, ring E, stud 0 spring a", pintle (Z coil I), pintle (1, spring J, clip f, screw F, and so to the binding-post H. In practice I use a scale about eight inches in length divided into fifty subdivisions. A current of one-twentieth of a milliampere passing through the mechanism will effect a movement of eight inches on the part of the end of the pointer, so that a variation of one-thousandth of a milliampere will effect a movement of one-fiftieth of eight inches, or eightfiftieths of an inch, or approximately one-sixth of an inch.

When it is desired to measure a current of greater strength than one-twentieth of a milliampere, the plug K is inserted in seat No. 1, and the variable resistance J so shunted into the circuit, the other resistances being shunted into the circuit as is desired, the sizes of such variable resistances being relatively decimal parts of each other. This resistance J illustrated I prefer to arrange so as to be one to nine as compared with the resistance of the mechanism. Under such conditions but one-tenth of the current is effective and the readings on the scale are taken in tenths and hundredths of milliamperes. The instrument is made ten times as sensitive as the above by means of six plug-seats each connected with and similar to 7b, producing a scale measuring accurately a current of one-millionth of an ampere to ten amperes. In order to adjust the pointer so as to cause its end to rest normally upon Zero, the current is cut off, and the retractile force of spring 6* is varied by turning the ring E, by means of the projecting handpiece 0, until such desired position of the pointer is secured. In case circumstances and conditions are such as to render the normal zero-point diflicult to see, the Zero-point may be moved by such variation of the force of the spring to an intermediate position on the scale so as to overcome such difficulty.

It is desirable when the instrument is not resting upon a fixed support, as when being carried about, to provide means for securing the coil, and hence the pointer, against move ment d uringsuch time. To this end I provide a plunger N, Fig. II, which is actuated to project or tend to be projected from the bottom of the base a short distance by a helical spring 92. The upper end of this plunger articulates with the end of a lever at, whose other end carries a ring M, which is located immediately below the frame (Z of the coil. The spring a is of such a strength that the weight of the instrument will effect its compression and depress the ring a into the position shown in Fig. II. hen the instrument is lifted off the support, said spring actuates the plunger to operate the lever n to raise the ring, cause it to engage the lower surface of the frame (Z, and effect contact between the latter and the core C. In such position the coil and pointer are held in a fixed position against vibration, so preventing any possible injury to the bearing;

Other modes of applying the principle of my invention may be employed instead of the one explained, change being made as regards the mechanism herein disclosed, provided the means stated by any one of the following claims or the equivalent of such stated means be employed.

ll therefore particularly point out and distinctly claim as my invention- 1. In a measuring instrument, a suitable base, a magnet supported there on,a coil mou nted and movable in the field of force of said magnet,a n indicating-pointer secured thereto, means for steadying said coil, means for moving the same independently of the variations ol the field of force, and means for securing the same against movement when the instrument is removed from a fixed support.

2. in a measuring instrument, a magnet, a conductor mounted and movable in the held of force of the same, a shunt-circuit comprising a plurality of electrical resistances of varying values, means for shunting any or all of such resistances between the terminals of said. conductor, an indicating-pointer secured to the latter, a single bearing for supporting said conductor, and means for lifting said. conductor, from said bearing and securing it against movement when the instrument is removed from a fixed support.

3. in a measuring instrument, the combination of a movable member and suitable supporting means therefor, an inclosing casing, an indicating pointer connected with said member, a retractile spring connected with each end of the latter, the trend of one of said springs being opposite to that of the other, a ring connected with one of said springs and normally secured against rotation, and a suitable handpicee connected to said ring, projecting from said casing, and adapted upon its actuation to rotate said ring to vary the retractile strength of said spring.

i. In a measuring instrument, the combination of a base, a rotatable member mounted thereon, an indicatingpointer secured to said member, means projected from the bottom of said base arranged to be actuated by the weight of the instrument, and connected with said movable member in such a manner as to secure the same against rotation upon being released from the weight 01 the instrument.

5. In a measuring instrument, the combination of a base, a rotatable member mounted thereon and movable from off its bearing, an

indicating-pointer secured to said member, means projecting from the bottom of said base arranged to be actuated by the weight of the instrument, said means being connected with said movable member in a manner such as when released from the weight of the instrument to lift said member from its bearing and secure it against rotation or movement.

6. In a measuring instrument,a base, a magnet, a conductor mounted and movable in the [ield of force of the latter, a shunt-circuit comprising a plurality of electrical resistances of varying values, means for shunting any or all of such resistances between the terminals of said conductor, an indicating-pointer secured to the latter, a single bearing for supporting said conductor, a plunger in the bottom of said base, a spring for actuating said, plunger out from said base when the instrument is lifted from a lixed support, said spring being normally compressed by the weight of the instrument, a lever actuated by the outward movement of said plunger, and a ring actuated upwardly by the movement of said lever and adapted to contact with and lift said conductor from its bearing and secure same against rotation or movement.

Signed by me this 10th day of February, 1903.

WESTON A. PRICE.

Attest:

Gr. W. SAYWELL, A. E. lVllGRKlQL.

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