US345755A

US345755A - Electrical indicator

Info

Publication number: US345755A
Authority: US
Publication date: 1886-07-20
Anticipated expiration: 1903-07-20

Description

(No Model.) 2 sheets-sheen 1. C. -WIRT.

ELECTRICAL INDICATOR.

1\To.-31=5,'755a Patented July 20, 1886,

(N0 Model.) I 2 Sheets-Sheet 2.

C. WIRT.

ELECTRICAL INDIGATOR.

No. 345,755. Patented Ju1y20, 1886.

UNITED STATES PATENT CEEICE.

CHARLES VIRT, OF CI-IIGAGO, ILLINOIS.

ELECTRICAL INDICATOR.

SPECIFICATION forming part 0I' Letters Patent Nvo. 345,755, dated July 20, 1886.

Application filed Octub( r 2, 1385.

To all whom, it 11i/ay concern:

Be it known that I, CHARLES WIRT, of Chicago, in the county of Cook and State of Illinois, have invented a certain new and useful Improvement in Electrical Indicators, of which the following is a specification.

My invention relates to an instrument or apparatus for measuring the electro-motive force existing at any part of an electric circuit.

The instrument consists, essentially, of a graduated variable resistance, and a shunt around a part of said resistance, including a standard battery, a galvanometer, and a circuit making and breaking key. The resistance is connected between the two points whose difference of potential it is desired to measure. 'NVhen the key is closed, the standard electro-motive force of the battery is opposed by the electro-motive force of that portion of the circuit whose electro-motive force is to be measured, and if these two are equal the galvanometenneedle will remain at rAero, there being no current in the shunt. If, however, one electro-motive force is greater than the other, the needle will be deiiected. rlhe variable resistance is then adjusted until the needle returns again to zero, when the electromotive force is known by the resistance in circuit, the resistancesections being graduated so as to indicate this,as will be explained.

My invention further consists in the novel devices and combinations of devices employed by me in carrying out the principle of operation just explained, as hereinafter set forth and claimed.

In the accompanying drawings, Figure 1 is a perspective view of a complete instrument embodying my invention; Fig. 2, a diagram illustrating the principle of the invention, Fig. 3, a top View of the instrument with diagram of the connections; Fig. 4, a View of the key which I prefer to employ, and Fig. 5 a section of the galvanometer.

Referring rst to Fig. 2, A B represent a Variable series of resistances connected across the circuit the electromotive force in which it is desired to indicate. In a shunt around a portion, G D, ofthe resistances are astandard battery, S, a galvanometer, G, and akey, K. In the resistance-circuit is a circuit-re- Seriul Nu. 178,853. (No model.)

'vel-sing switch, R. Vhen the key is closed,

the battery-current opposes the main current in C D, and the electro-motive forces are in the following proportions: The electro-motive force from A to Bis to the opposing standard electro-motive force as the resistance from A to Bis to the resistance from C to D. The ratio ofA B andC D is altered by Varying the number of resistance-coils in circuit. It' the galvanometer is deliected when the key is closed, then the resistance A Bin circuit is decreased or increased until it again stands at zero. Then the total of the nominal values of resistance A B in circuit represent the elec-A tro-motive force from A to B.

Referring to Figs. l, 3, 4, and 5, E E are two wooden boxes or frames mounted on a common base, F. Frame E supports within it the resistance-coils, which consist of insulated wire c a, coiled upon liat strips b I), which are held in slots c o. These coils are connected by connections through the top of the fra-me with plates d cl2-as shown in Fig. 8, so that the insertion of a plug between two plates cuts out of circuit that portion of the resistance which is connected to those plates. The battery consists of three compartments, H H H, constructed and arranged as set forth in an application made by me of the same date herewith, and is placed in a suitable case, I, in the space between the two frames E E. Frame E supports the galvanometer. The connections to the galvanometer are so made as to permit the instrument to be turned so as to bring its needle to zero,`whereby the neces sity for using external attraction for this purposeis done away with. Such connections are made by a curved spring, e, bearing on the circular metal case f of the galvanometer and carried by an arm, g, extending from bindingpost lL, and a curved spring, c', bearing on a metal ring, f', on the insulating-bottom ofthe instrument and carried by an'arm, g', extending from binding post h. From case f` and ring'f wires i and i extend, respectively, to the galvanometer-coils. The key in the shunt is a double key. From its lower stationary contact, j, a wire, 7a, extends to a point, Z, on the adjustable resistance. From its lower circuitclosing strip, m, Wire n extends to binding-post 0, from which wire p goes to one of the battery-terminals. From strip m Wire g goes to plate d of the rheostat, and from m2 wire r goes to plate d2. The other terminal of the battery is connected by Wire s with binding-post h. Plate d of the rheostat is connected by wires t t with binding-post h. The double key closes one circuit before the other, the extra contacts u being provided, so that m2 must make contact with m before the latter pushes m down upon j, and so as to lessen contact resistance. m and m have an insulating-button, e, between them. The connec- Ytions with the circuit whose electro-motive force is to be determined is made through conductors combined in a eXible cord, w, in any suitable manner. At the end of this cord is a connecting device, which consists of a body'of insulating material, x, having a crosspiece, y, which carries two metal pins or plugs, z z. The iexible cord enters and its conductors are therein connected with z c. To make connection the pins are thrust into the holes of the binding posts z2 z3 of the rheostat. .hen both contacts of the key are closed, the circuits are as follows: From z2 through such resistances a as are in circuit to d2 by r, to m2 and m by q to d', and again by cca to z3. This corresponds with circuit A B of Fig. 2. The shunt is from Z to j m u o p to battery s t" to galvanometer, i t t to d3. The key (mj,) battery, andgalvanometerare thus shunted around a portion of the resistance, as represented by C D of Fig. 2.

The operationis as follows: Connection with the circuit having been made as described, the galvanometer is first turned so as to bring its pointer to zero. Then the key is tapped and closes first the resistance-circuit and then the battery-shunt through a portion of said resistance,so that the two currents are there opposed. 1t' the electro-motive force of one is more than that of the other, the needle will be slightly deflected.y Portions of resist-ance aa are then cut out of circuit until the needle again returns to Zero, whereupon the electro-motivev force of the circuit under consideration is known, is denoted by the amount of resistance which is in circuit. If, when the key is first closed, the galvanometer is violently deflected, it indicates that the two currents are in the same direction. The plugs zz are then withdrawn, and the connecting device turned around so as to put each plug in the other binding-post, and thus reverse the circuit. This may often occur in practice, as when the indicator is connected with the circuit at a point where the direction of the current is not known. It is therefore desirable to have a circuit-reverser of some kind, and that above described is a very simple and convenient form. I may, however, employ any other suitable device for the same purpose-such, for instance, as the circuit-reverser R of Fig. 2.`

By means of the double key the resistancecircuit may be kept closed without closing the battery-circuit; or, if desired, the resistancecircuit may be closed by inserting a plug between d and d2. The binding-posts h and h are provided so that the galvanometer may be used for other work, if desired.

The use ofthe connecting device for the ilexible cord is not confined to this apparatus alone. It is evident that such a device may be used in any case where a flexible cord is to be connected to binding-posts, and is advantageous over the usual practice of having two loose ends for the conductors, sinceY these are not unlikely to come in contact and produce a short circuit when the cord is dropped from the binding-posts.

The resistance-coils are wound in single layers, and, being on fiat spools, there is little heating and little danger of a short circuit occurring. The preferred way of forming the coils is to wind the wire on paper tubes and then compress them into the tlat shape.

The whole apparatus is placed in an inclosing-box, (shown by dotted lines M M in Fig. 1,) and is thus conveniently transported from place to place. The frames E E may be conveniently removed from the box, and the battery-case also maybe readily taken out for rcfilling.

What I claim isl. In an electrical indicator, the combination of a variable resistance adapted to be connected across the two points of the circuit at which its electro-motive force is to be determined, a shunt around a definite portion of said resistance, means for producing a counter IOC electro-motive force in said shunt, and means f for indicating the current in said shunt, substantially as set forth.

2. In an electrical indicator, the combination of the variable resistance, the shunt including the standard battery, galvanometer, and key, and a reverser for the resistance-circuit, substantially as set forth.

3. The combination of the supporting-frame provided with slots of the flat resistance-spools held by said slots, substantially as set forth.

4. The combination, with a galvanometer,-

of sliding contacts permitting the turning of the galvanometer, substantially as set forth.

5. The combination, with a galvanometer having a metal case and a metal ring on its insulating-bottom, ofa contact-spring bearing on said case, a contact-spring on said ring, and connections from said case and said ring to the galvanometer-coils, substantially as set forth.

This specification signed and witnessed this 21st day of September, 1885.

CHARLES W'IRT.

W'itnesses:

FRANK A. HELMER, ALBERT N. EAsTMAN.

IIC