US1416824A

US1416824A - h indle

Info

Publication number: US1416824A
Authority: US
Publication date: 1922-05-23
Anticipated expiration: 1939-05-23

Description

C. F. HINDLE,

GALVANOMETEB. APPL'lcAnou men JULY 2, 1911.

Patented May 23, 1922.

'4 SHEETS-SHEET 1.

C. F. H INDLE.

GALVAN0METER-' APPLICATION FILED. JULY 2. 1917.

Patented May 23, 1922.

4 SHEETSSHEET 2.

8 nuewtoz Patented May 23, 1922.

C. F. HINDLE.

GALVANOMETER.

APPLICATION FIL'ED JULY 2. 1911.

C. F. HINDLE'.

GALVANOMETER. 1,416,824:- APPLICATION map JULY 2. 1912. Patented May 23, 1922.

4 sH'EETs-sHEET 4.

Fi 1 a.

CHARLES E. HINDLE, OF ELI'hI-IURST, NE? YGRK.

GAL'VANOMETER.

Application filed July 2,

To (ti Ti colic-m it may concern: 7

Be it known that 1, CHARLES F. HINDLE, a citizen or the United States, residing at 110 Maurice Avenue, Ehnhurst, Long Island, New forlg'have in vented new and use: lul Improvements in {'ifllVZLDOD'lStGIS, oi which the following .is a specification.

My invention relates to gali' 'anoineters or more particularly to those known as string galvanometers, whlch are devoted more or less extensively t medical and scientif c uses.

My improvements have for an ob1ect to provide a string galvanonieter of more perfeet adaptability to the specific purposes tor which it is designed Without affecting or sacrificing its essential operable features.

Another object is to produce a device of the class described of improved eiiiciency, and one in which greater facility and under latitude of adjustment arc combinedwith a high degree of accuracy and effectiveness,

both with relation to the parts adjusted and to the mechanism as a whole.

Ii further object is to provide a str ng LdlVfillOlIlGllQI' in which the inner niechanlsni thereof. of which portions are necessarily of extremefincness and delicacy, is adequately protected "from atmospheric and other deleterious influences.

tlalvanometers are made of various designs and are employed for d'ifl erent purposes the type to which my present invention relates being known as the string gulvanometer. in which vibrations of a delicate CON or string are employed to detect the presence of and definitely to measure minute values o't electric current or voltage. Such instruments. in their fundamental c0nstructiou. are based upon the "familiar phen0inenon oi the definite tendency of an electric conductor (the string of he galvanoineter) to move laterally within a magnetic field. the deflection thereoli' being proportionate to the strength of l he current passing through such conductor. the strength of the field remaining; constant. The extent and frequency of the deflections ot' the string of this type oi" on] nnmucter. are ascertained and measured bv means oi" h a vi nu shadows of the lateral vibrations thereo'l recorded. photograph iuull v in highly magnified torin upon mov inc him. The string: galvanomcter is therefore particularly adapted to being employed to detect and accurately evaluate extremely weal: electrical impulses by the use of a cor responding-l delicate filament or string of Specification of Letters EEltfini.

llfntented lllay 2?, 1922. Serial No. 178,136.

vsuitable material which is held as indicated between the poles of a n'ia g'netol predetermined stren th transv rsely to the lines of irce thereof. To obtain this result the string thus connected is etsablished in series with the source of electric energy to be in vestigated, and while suspended Within the magnet held as described is also placed in :local arrain gement so as to intercept the direct rays of an intense white light that is intinduced throi'lgh telescopic tubes and iocussed upon the string in such manner that the latter will cast minute shadow which in turn by magnifying lenses is projected upon a sensitized film that moves at a pr determined rate before too shutter of a camera. such film having graduations or other markings previously applied thereto provides means for establiShint and recording the relative Widths and recurrencies in point oi time of the successive shadowgraphs recorded thereon.

'lheret'ore my invention considered in its more general aspect comprises a horse-shoe electromagnet supported. horizontally upon standards provided therefor, having its respective poles oppositely disposed and in relatively close proximity, and having adjust-ably supported thereon the frame-work or housing that contains the string and also the mechanism. {or adjustably retaining that delicate member in proper focal position "For the proper projection oi? the shadow to be photographed th eretrom improved means are also contemplated in my invention in the open form of the electro magnet windings employed whereby a constant strength of magnetic field is maintained at a hightension Without unduly heating;- the apparatus While in use and through unequal expansion of portions o" the magnet. thereby disturbing the proper relationship between the positions of the string and the photographic apparatus.

At a suitable distance from the shadow projecting mechanism to obtain the desired multiplication thereot. is placed any suitable t vpe oi camera adapted to present a moving film tor photographing continluiusly vihritory movements of the string.

For convenience oi description. my invention will he considered as cou'lprisingg two brunt-hes. that relating;- to the gzalvanometer. and the apparatus for photographingthe movements oi? the string; or" the galvanometor: and in like manner the galvnnometer itself will be described first with reference to the features pertaining to the magnet proper, and then to the mechanism for properly containing the string in an airtight compartment in combination with means for variously adjusting that member.

Referring to the drawings illustrated of a preferred embodiment of my invention, Figure 1 is a plan view of the galvanometer proper;

Fig. 2 is a front elevation of the galvanometer with portions shown in vertical sectional views;

Fig. 3 is a partial side elevation and sectional view of the device shown in Figs. 1 and 2 showing internal string adjusting mechanisms and detail of the winding upon the magnet.

' Fig. 4 shows in plan the detail of a vertical string adjusting mechanism seen in Figs. 2 and 3; 4

Fig. 5 is a detail of the lateral string adjusting mechanism seen in Figs. 2 and 3;

Figs. 6 and 7 are respectively plan and side views of a member of the adjusting mechanism shown in F 2 and 5;

Figs. 8, 9 and 10 are respectively plan, side and end views of the under member of the lateral adjusting mechanism, supporting the part shown in Figs. 6 and 7.

Fig. 11 shows the insulated. supports to which the string is attached; Fig. 12 is a rear View of the string bracket supporting plate detached from the magnet;

Fig. 13 is an end view of the plate shown in Fig. 12 with upright member of string bracket supported thereon;

Fig. 1 1 is a front view of the upright plate of string bracket; Figs. 15 and 16 are respectively top plan and wedge end views of a pole piece;

Fig. 17 is a partial detail of parts shown in Fig. 1; and

Fig. 18 is a front elevation of the galvanometer illustrated in comparatively reduced form in connection with a lamp and camera apparatus shown at the respective sides.

The electromagnet, in the preferred form of my invention, illustrated in the d awings to which reference is made, is represented by the numeral 1, which is designed to be energized by direct electrical current in the usual way, the soft iron body of which is composed of a casting 2, annular in form, and having circular cross-sectional areas. The forward portion of the casting 2 has been cut away as by a vertical plane intersecting the casting to form the. horseshoe type of magnet required by my invention. and thereby providing suitable surfaces for receiving two similar pole pieces 3, l, constituting the respective poles of the magnet. The pole pieces are secured rigidly to the member 2 by the bolts 7, and are oppositely disposed in longitudinal alignment relatively one to the other, presenting wedgelike faces at the point of approach, the respective apexes of whichare slightly flattened to constitute two of the walls forming the narrow rectangular chamber 5 for containing the string of the galvanometer.

The magnet proper is adapted to be supported in a horizontal position upon the three legs 6, one attached directly to the rear portion of the casting 2, and one similarly connected with each of the pole pieces 3, 41. The wiring coils of the magnet are applied in a series of separable windings which I may designate as spools 10, each spool preferably composed of copper wire 11, insulated in the usual manner, and all spools being wound in the same general direction, the windings of each independent spool being separately insulated in a convenient manner, the respective ends projecting from the spools, being united to form a continuous metallic circuit connecting several spools; thus the end of the wire of one spool connects with the oppositely disposed end of the next adjoining spool, which order is followed in connecting adjacent spools throughout the series surrounding the casting 2 of the magnet. The several spools have been separated one from the other in the manner indicated, to permit free circulation of air in and around the windings, thus preventing over-heating of the magnet and allowing an appreciably higher degree of electro motive force to be maintained in the electric magnet. The continuous circuit thus extending from one end of the magnet to the other, terminates at its opposite ends in binding posts 12 and 12, the latter having been suitably attached to the insulating blocks 13 on respective legs (3 of the magnet to which binding posts are connected the opposite poles of the source of direct current electric energy employed to energize the magnet. V

The necessity for obtaining a high magnetic field in devices of this clas. has made it practically necessary to use current in such quantity as to produce excessive heating of the magnet, disturbing the adjustment of the string in proper focal relationship, with the result frequently of incapacitating the entire mechanism. For this reason in using other forms of magnet winding it has been found necessary to operate the device at a lower tension than was required to produce the desired results. Therefore, to obviate this diliiculty, l have provided the means described for obtaining high electric efficiency with a minimum of the heating disturbances referred to.

While I have thus described the construction of the preferred form of magnet to be used in connection with the galvanometer of my invention, other modifications may obviously be made to obtain the same general re- 18 and 19 correspondin sult, although not as effectively and completely as in my preferred embodiment. desire nevertheless in thus describing completely a preferred form, not to limit myself to that particular design of eleetromagi at, or in fact to magnetot the general type illustrated. v

The adjustable string supporting and con taining mechanism, as has been pointed out, is more or less intricate, due to the concen tration of the diverse structural and functional elements by which it is characterized. The first requisite or its designing is to sup-- ply a draft-proof chamber for the string; next it must be provided with m ans for introducing horizontal rays of light Focused at a point to be intercepted by the string, so as to :to H1 a shadow to be projected in the opposite direction through magniityin lenses on a camera mechanism to be described in another connection; also the position of the string requires frequent readjustmeits from side to side to keep it in exact focal alignment with the light ra; and ttfurthermore, delicate means are equally important for regulating the tension of the string, which is exceedingly line and fragile, but must nevertheless be maintained at the required tautness.

n describing the string mechanism 1 will first refer to the means employed in forming the string chamber and supporting the shadow projecting lenses in suitalole rela tionship therewith; and then proceed to describe the mechanism employed in ellecting the adjustments of the string.

The Wedge-shaped ends oi. the pole pieces 3. 4;. instead ot terminating in a sharp d are flattened slightly to term the narrow walls 3 and i upon the respective apexes thereof. and when the pole pieces are in pl e normally the surfaces 3 a nd l are separate-" by asmall gap between the poles oi the in net, of approxii'na'tely two millimeti J width, thus constituting the two side walls oi" the string chamber. The front and i walls of the chamber 5 are supplied by "iller blocks l8, 19, similar in form to the tapered ends of the pole pieces .znd thereby adapted the two sides thereof. haying liattenec apexes and l of the pole pieces, (see l t l and l7). Thus when the tiller hloclrs are in place the i'alls su i iorted by their respective sur faces 18 and l9 when hrougl t into proper relationship with the Will s U and l, the rectangular ertical CJHlTPQl' will accord ingly be formed. The trout block l8 is secured to the pole pieces by iii-cans o the bars 18* to which the block is attached by screws. and which in turn is secured l lar screws to the respo 'i'e pole rearward wed bloc. is in held in place is means the pol th adjustments oil the delicate string member 1 have found to hare been "uently d' i returned by reason oi the almost inipcrcept ole llexures of the pole :Jliltlli'lg plate 1.5, and other changes in the relative arrangement oi these parts and to remedysuch detective design oi? this important feature of the string galranouieter construction. adopted, l have provided a brat-hot plate .250 and ha Ye thereby eliminated. the rigid attachment of this plate bracket to the pole connecting plate 15 so that any displacement or movement of the :iormerinay not be coninuini 'ated to the latter. Thus l employ a single stud 2i (Figs. l and 3) which is secured r' lly to the central portion oi the plate 15 (see Fig. 123) projecting rearxtmrdly through an orihce 22 in the plate 20 and the boss 26. The orifice is .u ade larger than the diameter of the bolt so that any tendency of the latter to more out of its normal place will not e communicated t the plate :20, an d thereby communicated to the string turbinp; the delicate setting of the string. Upon the threaded outer end ol the stud 2i means oi" which a compresi i ad ustably held against the on the bratl k7 boss 23 h a 'ing been pimiccc.

t pt: Le 20, a

collar 20 l bearing for the end oil The dapted to press the pl; l? the pole binding nicn'iber l the spring. D

a thcre'ltore he direction ,1 members or feet of the p ate 2t) coin n'ise the three screws 2?. 2H and :29. each pr; ably oi hardei'ied steel. suitably held in the. co respondingly threaded oritice in said plate. it the lower central portion oi the ate is plated the screw :27 the rounded end.

inch, bears d tlv upon the sur'tace of tin" date it) and proye'ts beyond the outer suinice he c 2 0, having a lock-nut at end. 1e other 'l'cct 11b and hi are siiuihirly suiiportei in threaded or'uices at portion oil the plate 20 at the side. ..rc.f ant instead of ed end as pro- Xlcd For c i .4! etch has a coped or the point of resting 1. mingling? conical depression 2 in "ll herd of a hardened plate i5, while are similar porn. of tie screw 28 is held within the horizontally disposed V-shaped groove 28 of the flat head pin 28.

It is thus provided that the plate 20 is held in normal position against vertical displacement by means of the point of the screws and 29 being ilrmly held in the groove 28 and depression 29, while in case of any tendency of the plate 15 to expand or contract or otherwise become distorted, the groove 28" permits the lateral slidingot the screw point 28 therein, and to maintain its normal position unaffected thereby. Like wise the round nose screw 2? at the bottom of the plate 15 being free to slide on the surcylindrical boxes or housings ot the string mechanism, which are thus operably supported upon the pole pieces immediately above and below the string chamber 5. The rectangular string chamber 5 thus constitut s a communication between the res ective chambers of the said housings which contain the su 'iports to which the string 30 is attached, which supports, as has been pointed out, are insulated from the electricconductive portions ol the apparatus, and are further made adjustable so as to more the string}; in all directions, and to regulate its tension by means oi." a longitudinal adjustment of one ot the string; supports. I will now describe the string supporting mechanism.

Upon the respective bracket plates 31 and are supportably mounted the two hollow cylinders or

shells

33 and 33 similar as to their general aspect-both in t'orm a d in tunction, with the exception that the upper shell 33 has at its top an extension or chamber 34 within which. as will presently be seen. is housed the mechanism for controlline the tension of the string, the

shells

33 and 33 containing the similarly acting means tor moving the string laterally. which I will now describe more in detail, in con nection with the string),- supporting mechanism.

The string 80 is a thread-like formation ol quartz drawn to extreme fineness and having a metallic coating usually of gold or silver to render it electrically conductive, the diameter of string thus coated rarely exceeding .003 millimetres, and its length approximately 13 centimeters. he string is attached at each end, by a suitable adhesive, to the flattened side 41 of a pin 4.0, held in insulated brackets or string holders 35, 35 (see Fig. 11). The construction of the string holding brackets being identical in form, I will therefore describe in detail as applicable to both the mechanisms, the upper holder oracket The string bracket holder, it will be seen by reference to Figs. 52 and. 11, comprises an L-shapedmetallic body piece 35 upon the vertical arm of which is attached in any convenient manner a block 38 of insulating material which in turn has suitably mounted upon its outer surface a slotted clamping block 39 into which the pin it) is held by means ot' the small thumb screw a2; a second small screw 37 having been fitted in a suitably threaded aperture in the block 39 performs the function of a binding post of the wire over which is conducted the current to be measured.

llnto the horizontal arm or the body piece 35, 86 is secured the stem as which in turn is slidably secured to the upper laterally slidable member l5 of the two way slides consti-' tilting the string adjusting mechanism next to be described, the stem 43 of the lower adjusting mechanism being rigidly attached to the corresponding member 35 of that mechanism. i

The mechanism employed for moving the string into the focal point of the shadow projecting mechanism, excepting as to a :teature presently to be explained, is likewise con'iposed of similar parts for the respective ends of the string 30, and the uppermost mechanism will accordingly be described as applying to the similar parts and features of both mechanisms.

'lhns tor the lateral adjustment of the string holding; bracket 35 I employ a two way slide member 45 into which slidably tits the stem or shank 43 of the string bracket 35 which slide 45 is seated upon a second slide 46, which in turn is seated upon the plate l? ot the shell or housing 33, suit able clearance apertures having been centrally provided in the slide ll) and plate at? to permit the stem d3 free passage therethrough. The member 46 is guided so as to be slidable in one direction only by means of lflshaped gib 48 on its under surface which fits into a corresponding V-shaped groove l9 provided in the plate 47. Likewise upon the under surface of the slide 45 is a similar .e-ib 50 adapted to be guided by a correspondingly formed groove 51 in the slide 46, the direction of the groove 49 in the top surface of the slide having been disposed at right angles to that of the g'ib 48 on the bottom of the slide, limiting the movement thereof to two directions and permitting the like movement of the slide a5 seated thereon in the two opposite directions. As pointed out, the stem 43 of the the upper inechai stringholder hracliet 85 is adjustably supported h the slide and for this purpose a bushing 7c is secured thereto into which the s cm i -l slidably lits. The slides 45 and 16 are fii'nil held in their respective seats by mean of a top plate 52 supported upon side piec .-rhich hold it parallel to the sur face oi the plate 4:7 against the under sur- "'ace of which the slide bears. T he slides l5 and it; are movable ae'ainstspring action in efi'ecting adjustments, the supporting slide being held by two compression sprii 3 5 similarly supported at one end by the lip piece 5, their opposite ends hearing against the v.djacentside of the slide. A similar lip piece 55 is also pr vvided upon the top plate t? having the thumb screw 56 suitably mounted therein for engaging the side of the slide opposite the spring. the stem of the screw projecting beyond the housing to render it accessihle to the operatr for adjustment. A. like spring holder lip 57 similarly provided upon the slide 46 having; compression spring; 58 adapted to engage the slide 45, a lug: 59 on saic slide 46 holding a thumb screw 60 in suitaliile arrangement to engage the side of the slide 45 opposite the sprinp; the thumh screw (3 also iroject'ino through heyoijid the shell 33.

Thus

are provided means for adjustahly moving the stringholding bracket forward or luck and to the right or left by means of two

thumh screws

56 and 60.

Thus far the parts described in connection with the stringadjustin; mechanism whicl'i are contained within the housing above the pole pier-es. have their exact rount rpart in the similarly ictinn' mechanism housed in the low iell 33 excepting that the order or arrauiie nont ot the parts of the latter inverted relatively to that of ism and as already reoi the upper string ferrerl-to. the stem 4: hracke 85 is longitudinally adjustable in the sliding); mcmher 45. while the. stem 43 of the lower bracket 35 is ri 'idly attached tothe slide 1 5. thus supply means for contro ring; 30.

nu; the tci'ision of the The string tension regulatin means also the vertical screw t held 66 in the head 67 secured o the noun '3 6S intern d pced in th upper poiiion of t..- shell hich shaft has upon its shanl: above the thread the worm gzciir 6Q mounted to slide longzitudinall l thereon hut held froinu'ota inorelatively thereto by means of a spline '70. The gear 69 rests upon head 6? and is held lone: .udinallv in place hy means ot the top pl ol the shell ll. and is actu ated tor the purpose of otating; the screw shaft (55 within its hrearled aperture, by means of a worm 711. pinned to the end of a shaft 72, suitably mounted in a bushing n3) flu: cud oi the screw itself. however, does not hear directly upon the head 74,

hut upon a small hardened steel plate 77 lQSt'iYlQ eentrallv upon that member; being yud in place thereon by means of a short stem '18 extending into the top of the shaft til. in the end of the screw is embedded securely a small hardened steel. ball, which is brought into immediate contact with the top surface of the small plate 77. The diameter of the disk plate '7? is determined by the extent of lateral adjustment required ot the stem 4t?) in its movements both to the right and le t. and fo ward and back; and the stem l- 'l is held apiaii'ist whatever tendency to re. cite. the same may he caused. when the adjusting screw turned by means 0 l two pins 79 extending! upwardly from the hushingg- 77 into si'iita-ble apertures in the head 74- thereof.

In the pole pieces 3, elare the telescoping posed ce 'it-rallv thereof. The tube 80 in the pole piece 3 in the form illustrated, receives the light and by means of the usual arrangement of suitable lenses adapted to bring the rays "from a lamp apparatus 90 (as shown in l ipg. 18) or other source of light into Focus at the point to be traversed by the string 30; and in like manner the tube 80 is held by the pole piece 4: and receives the rays of light as they diverge from such focal point. and project them, highly magnified, upon the photographic film of a suitable camera.

The respective tubes 80, 81 are inserted in longitudinally disposed cavities in the respective pole pieces to which they relate, and h are the usual means for adjusting the rela ti e :ing Tenient of the lenses, my invention 11 i. :eference to those partit an stated. It has been a 1 t1 gt the telescopic tubes themselves require lateral adjustment at tit and for this purpose I have mounted the upon annular bearings 81.. which are attached in like manner to the outer ends of the pole pieces 3, 4;. The mechanisms for supporting the respective tubes are identical in structure and operation. and I will describe in detail the parts attached to the pole piece 41 shown in section espective tubes Ell in Fig. 2. supporting the tube 80, with the intention that such specification apply also to the adjustable supporting means for the tube 30, upon the pole piece The annular bearing 81' has two parallel inner surfaces adapted to receive therein a corresponding member 82 which is made in the form of a collar surrounding the tube 80 to which it is rigidly attached substantially midway of its length, the end surfaces of which are adapted to bear against the inner faces of the annular member 81, the width of the collar 82 being designed to fill the space between said surfaces, and the diameter of the central opening of the latter having: been made larger than that of the tube toadmit of the necessary latitude of adjustment thereof. In the periphery of the annular bearing); 81 are three threaded oriflees equally spaced circumferentially thereof, into which are inserted three similar thumb screws 8% except that the stem of the one at the front projects less from the surface of the bearing than those in the rear of that member. Thus it is provided that by loosening or withdrawing one or, it may be, two of the screws and tightening the remaining screw or screws, the tube may be shifted bodily in all directions laterally thereof.

The rays of light passing through the tubes 80, 80 when properly adjusted will by action of the lenses of the tube 80 be projected through the shutter of the camera 95, in which is a moving sensitized film preferably having; graduations both 'l'iransversely and longitudinally, which film is caused to pass before the usual shutter of the camera at a predetermined rate of speed, and that when the string 30 has been properly brought in to the focal point between the tubes 80 and 80, successire shadows thereof will be photographed. It is deemed suiiioient for the purposes f the present specitication-to indicate the general type of camera used, and means for actuating any of the familiar types of cameras adapted to photographically record successive views. Thus, I employ a camera box 98 having two

shafts

97 and 98, the later having pinned thereon a pulley 99 which may be dri en by any convenient means. suclthe small electric motor 10) from a small pulley on the shaft of which is the belt shown in Fig. 18: The film then placed. in the camera boi; upon the usual spool upon the shaft 97 and brought immediately in front of the shutter indicated at 101 and attached to a second spool. on the shaft 98, upon which it is wound after passing before the shutter of the camera.

lnthe front of the casings 33, 33' are similar openings 33 extending all the way to the base of each housing, and at the respec tive sides thereof are small openings 33 A emme rotatable inner shell or door 33 is held within the respective shells 33) and 33, which have openings Ell-1 and 33 corresponding in size, shape and relative arrangement with the

openings

33 and 33 so that when the closure shell Eli-l is rotated to the proper position, its opening 33 coincideswith the opening 33, thereby bringing the openings 35" and 33 into coincidence, as shown in u nen the doors are thus opened and the wedge tiller 7 8 has been removed the string holding mechanism is sufiiciently exposed to admit of free access in removing and replacin strings when required. Thus also it will be seen when the piece 18' is replaced and the door member closed by rotating the same into such positiom the string containingcavity has been rendered immune against air drafts or the accumulation of moisture or other damaging effects.

Having described my invention, what I claim is:

1. In a galvanometer having an electromagnet with oppositely disposed pole members, adjustable means for suspending a string between said pole inembers said means being laterally andv longitin pally ad just-able relatively to said pole members into a plurality of parallel positions relative to itselt.

In agalvanometer for measuringfeeble electrical currents an electro-magnet and oppositely disposed pole pieces thereon; an electro-conductire string; member suspended between said pole pieces adapted to carry clcctric currents therethrough; means for projecting rays of light through, said pole pieces. comprising lenses in telescopic tubular cases; and enclosed means for adjusting into a plurality of parallel positions said string relatively to itself and to said pole pieces and said lenses.

in a galvanometcr for measuring feeble electric currents, an electroniagnet and on positely disposed pole pieces thereon; dn electroconductive string menber suspended between said pole pieces; means for project rays of lightthrough said pole comprising telescopic tubes with iad .pted to cause said rays to con focal point intermediate said self-adjusting means .mounted pole pieces for adjustably suspend electro conductive string: inernb i ansrersely through said focal point intercepting: a. portion of said rays thereby to cast a shadow of said string; and means for controlling the tension of said string.

l. In a galvanometer for measuring; feeble electric currents, an electro magnet and oppositely disposed pole pieces thereon; means for projectingrays of light through said pole pieces, comprising telescopic tubular cases with lenses adapted to cause said rays ill) ported up scopic tuhes with lenses adapted to to converge at a focal point intermediate said pole pieces;' selt adjustingmeans mounted upon said pole pieces for adjust ably suspending an electro conductive string; transversely through said focal point, intercepting a portion of said rays thereby to cast a shadow oi? said string; means com" prising a sensitized movingtilm for photo graphing said shadow in a succession oi exposures; and means for controlling the ten sion of said string.

5. In a galvanometer for measuring feeble electric currents, an electro magnet and oppositely disposed pole pieces thereon; means for projecting rays of light through said. pole pieces and focussing said rays inter mediate said pole pieces; self adjusting means carried by said pole pieces for adjustably supporting an electro-condu tive string in the focus of said rays; insulated supports for said string; means for housing said string and the supports thereof, said housing means adapted to prevent air cur-- rents contacting said string; and spring actuated means for regulating the tension of said stringand a thumb screw for controlling said spring actuating means.

6. In a galvanometer for measuring feeble electric currents, an elect-ro-magnet and pole pieces thereon; an electro-conductive string); having terminals adaptable to form electrical connections with animal bodies; iusulated brackets and means carried by said pole pieces "for adjustably supporting said brackets to which brackets the respective ends of said string are attached; and independent means tor laterally adjusting: the positions of said respective braclmts, each comprising a pair of slides, cue or ad slides operably su iportcd upon the other thereof.

7. In a galvanometer ior measuring); teeblc electric currents, an electro-magnet and pole pieces thereon; an electro-conductive string having terminals adaptable to Form ele trical connections with animal bodies; insulated brackets and means carried by said pole piecesfor adjustably supporting said brackets to which brackets the respective ends of said string are attached: independ ent means for laterally adjusting the positions of said respective brackets, each comprising a of slides, one slidably sup pair othe other of said slides: and means for adjustably moving the bracket at one end of saic. string longitudinally tively to the bracket at the other end of said string.

In galranoineter For measur' ble electric currents, an electro-magrnct in oppositely disposed pole pieces; telerays of light projected therethrough: porting means for inter-posing fiSlTClZl of minute cross-sectional area of electro-conducti material. in said Focus; insulatec brackets For supporting said string; manna n'icans for adjusting said brackets laterally a ed manual means tor adjusting; one oi sui brackets relatively to the other.

9. in a aalrailoineter ior measuring iecl'ilc elects" K l on said pole pieces l brackets adjacent tro-conductirestring at ,ri' ed to said brackets tor receiving the electric curw )t to measured; manual means com sing slides each adapted to more right ang es relatively to the other for la adjusting said lu'ackets i tersaid pole pleCGFl, means tor controlthe tension oi? said strin In a n'icdiatc f, opposed pole members. up string, means for supporting;

t .ion in the space hernenber and. means for said c said ruppo tine; means in a of: direct ons transre oi the Without "varying the tension of the a n'alvancunetcr hariug an clectroiaguet r 1 space i oppo'-" Jaced terminals, 1. condv a 5 string. passbers and connected porting means 'lor a stationary meni- 'd terminals, :11 i h ternunal com he, an elcn'ient af. iereon in one irection and in a i averse to the and a se ond elcni a direction 1 trom that of said first element and am also transrrrs. to the string. said inal being;

., izrier! hr second elen a gralranomcier having; an eleciroiuagrnrt with apawd oppo pole iucuihers.

an terminals. :1 c-zu'idu uiiw stringpass .21;; "tn'ccn the pole uiemhrrs and connected to tcrininds. supportin n termini 1 com .icnaiar 111cm her. an element i=l' 'liercou in one direc- .52. can. let each J i :1 ca en i, :l the elen entu tor rar vii'ur the eliect oi the. resiliei'it means upon the string.

in a. ,g alrai'ionieter iiarii'igr s-qpaccri opposed pole niemhei a conductinir string, means for support agsaid string in the space between the pole members and under tension, optical mechanism extending through the pole members for observing the movrmcut ol the conducting string when current passes thcrcthrough, anduicans for adj ustiug the optical mechanism in said pole members in a direction bl'filli-QZVQKSQ to itself to place the image of the string in any desired portion of the ObSOl'Vii'iJlOIl iield oil the mechanism.

1 1. In a galvanometer having spaced pole members, supports carried by said pole members, a conducting string passing between said supports and in the space between the pole members, the connection between the string and one of the supports comprising an element adjustable on said one support in one direction transverse to the string, a second element adjustable on said first ele ment in a direction transverse to the string and also in a direction different from the direction of movement of the first element, a sleeve carried by the second element and parallel with the string, a terminal. member to which an end of the string is connected slidable in said sleeve, and spring means beween the sleeve and the terminal member for shifting the latter to tension the string.

15. In a galvanometer having spaced pole members, supports carried by said pole members, a conducting string passing between said supports and in the space between the pole members, the connection between the string and one of the supports comprising an element adjustable on said one support in one direction transverse to the string, a second element adjustable on said first element in a direction transverse to the string and also in a direction different from the direction of movement of thefirst element, a sleeve carried by the second element and parallel with the string, a terminal member to which an end of the string is connected slidable in said sleeve, resilient means between the sleeve and the terminal member for shifting the latter to tension the string, and means adjustably carried by said one of the supports and co-acting with said terminal member in all of the adjusted positions or the member for varying the eliectiveness of the resilient means upon the string.

16. In a galvanometer having spaced pole members, a conducting string for connection to an external circuit arranged across the space betweenthe pole members, terminals to which the ends of said string are con nected, a sleeve in which one of the terminals is slidably mounted for movement in the direction or the string; a spring acting be tween the said one 01": the terminals and the sleeve for tensioning the string, a plate upon oi movement of the plate, a contact member the pole members, means for shifting one of said terminals in a plurality of directions transverse to the string, resilient means tending to tension said string, a thrust member against which the said one of the terminals abuts in all adjusted positions, and means for adjusting said thrust member to negative to various extents the effect of the resilient means upon'the string.

18. In a galvanometerhaving spaced pole members, a conducting string, terminals between which the string is stretched with the string extending across the space between the pole members, means for shifting one of said terminals in a plurality of directions transverse to the string, resilient means tending to tension said string, a thrust member against which the said one of the terminals abuts in all adjusted positions, and means including a worm wheel carried by the thrust member and a worm meshing therewith tor feeding the thrust member slowly toward or from the terminal to negative to various extents the effect of the resilient means upon the string.

19. in a gilvanometer having spaced pole members, spaced terminals, a conducting string connected between the terminals and e:-;tending across the space between the pole members, housing means carried by the pole members and enclosing the string and terminals, a plate mounted on said housing, means for movement in a single direction transversely of the string, a screw for forein the plate in this direction, resilient means for opposing this movement of the plate, a second plate mounted on-said first plate for movement in a direction at an angle to that oi the first plate, a screw for forcing the second plate in its direction of movement, resilient meansopposing the movement of the second plate b the screw, a sleeve carried by said second plate with its axis substantially parallel with the string, one of said terminals being slidingly mounted in said sleeve, spring means acting between the sleeve and said one of the terminals for shifting the latter in the sleeve, to tension the string, and means for varying the tensioning effect of the spring means upon said string.

20. in a galvanometer having spaced pole member, spaced terminals, a conducting string connected between the terminals and extending across the space between the pole members, housing means carried by the pole members and enclosing the string and terminals, a plate mounted on said housing, means for movement in a single direction transversely of the string, a screw for forcing the plate in this direction, resilient means for opposing this movement of the plate, a second plate mounted on said first plate for movement in a direction at an angle to that of the first plate, a screw for forcing the second plate in its direction of movement, resilient means opposing the movement of the second plate by the screw, and means for securing one of said terminals to said second plate.

In testimony whereof, I have signed my name to this specification, this 25th day of May, 1917.

CHARLES F. HINDLE.