US1758416A - Recording galvanometer - Google Patents

Description

y 1930. F. F. UEHLING 1,758,416

RECORDING GALVANOMETER Filed Oct. 3, 1929 2 Sheets-Sheet 1 VENTOR 5 Z I EM May 13, 1930. F. F. UEHLXNG 1,758,416

RECORDING GALVANOME'L'ER Filed Oct. 3, 1929 2 Sheets-Sheet 2' IL Wm INVENTOR Patented May 13, 1930 PATENT OFFICE FRITZ FREDERICK UEHLING, F PASSAIC, NEW JERSEY RECORDING GALVANOMETER Application filed October 3, 1929. Serial No. 397,127.

This application is a refile of abandoned application No. 188,036.

My invention relates to recording galvanometers or millivoltmeters, and embodies c a novel method of transmitting the delicate lends itself to any of the well known applica tions of the galvanometer, I am confining this description to one particular form, namely, that of a recording pyrometer in which the electro-motive force of a thermo-couple is recorded by the recording galvanometer, the

latter being calibrated in degrees of temperature instead of in electrical units. My invention particularly relates to means for utilizing the delicate needle of a galvanometer,-as a contact member for definitely closing electric circuits which control the recording device, the latter being operated by an independent source of power.

Figure 1 is a plan View of a particular form of the invention, with the electrical connection shown diagrammatically.

Figure 2 is an elevation of Figure 1, with the electrical connections shown diagrammatically.

Figures 3 and 4 illustrate different positions of mercury switches, said switches to be hereafter referred to as connectors.

Figure 5 is part of a section on line A-B of Figure 1, and illustrates a pawl and ratchet with its operating means for turning the galvanometer in a given direction.

. Figure 6 is part of a section on line OD of Figure 1, and illustrates a second pawl and ratchet with its operating means for turning the galvanometer in the opposite direction. 1

Figure 7 is a diagrammatical View of the wiring and illustrates the more important elements. of the different circuits.

llhe same numerals refer to the same parts in all illustrations.

I utilize a galvanometer, Figures 1 and 2, which is of the well known form, consisting of a permanent magnet, between the poles of which is pivoted a coil 2. An indicating needle 3 is fastened to the coil, the deflection of which depends upon the current passing through the coil and the balancing force of a hair spring 4. The galvanometer is permanently fastened to a shaft 5, Figure 1, which shaft is rotatably mounted in a long bearing 6. The galvanometer is fastened to the shaft by means of a yoke 7 as illustrated, and is held in such a position that the axis of the pivoted coil of the galvanometer coincides with the axis of the shaft. A worm gear 8 and a pulley 9 are also fastened to the shaft 5, both concentric with the shaft. The galvanometer, the worm gear 8, the pulley 9 and the shaft 5, all of which are fastened together as stated, are prevented from shifting laterally by the pulley 9 on one side of the bearing 6 and a collar 10 on the other side of the bearing, said collar being fastened to the shaft by a set screw 11. A worm 12 which meshes with the worm gear 8 is fastened to a, shaft 13 said shaft being rotatably mounted in bearings 14 and 15. It is thus obvious that as the shaft 13 rotates in one direction or the other,

the galvanometer and the pulley 9 will also rotate in proportion.

The shaft 13 is propelled in one direction or the other by one or the other of two pawls 1G and 17 which engage the teeth of ratchet wheels 18 and 19 respectively. These ratchet wheels are fastened to the shaft 13 and are rotated in one direction or the other depending upon which of the pawls is in action, all in a manner which I am about to describe.

The relation of the pawls 16 and 17 to their respective ratchet wheels 18 and 19 is more clearly illustrated in Figures 5 and 6. Pawl 16 is so constructed with relation to the wheel 18 that lateral reciprocating motion of the pawl 16 at right angles to the teeth of the wheel will cause the shaft 13 to turn in the direction indicated by the arrow Figure 5.

Un the other hand pawl 17 is so constructed with relation to the ratchet wheel 19 that lateral reciprocating motion of the pawl 17 at right angles to the teeth of the wheel, will cause the shaft 13 to turn in the opposite direction as indicated by the arrow, Figure 6. It is obvious that since the ratchet wheel 18 and the ratchet wheel 19 are both fastened the magnets 24 to the shaft 13, it will be necessary to lift the pawl 16 away from the wheel 18 while the pawl 17 is in operation, and likewise to lift the pawl 17 away from the wheel 19 while the pawl 16 is in operation. This is accomplished, in the case of pawl 16, by an electromagnet 20 which, when energized, attracts an armature 21 which forms part of pawl 16, and in the case of pawl 17, it is accomplished by an electromagnet 22 which, when energized, attracts an armature 23 which forms part of pawl 17. The motion of pawls 16 and 17 is respectively caused by electromagnets 24 and 25. The manner in which magnets 20 and 22 are energized, and the manner in which motion is imparted to the pawls 16 and 17 by and 25 will be presently described; p

. For making and breaking the electric circuits which actuate the electromagnets, I utilize two mercury connectors 26 and 27. Al though such connectors may have any of many forms, the particular form which I prefer to use is illustrated on an enlarged 'scale, and in different positions,'by Figures 3 and 4. .Each connector consists of mercury 28 hermetically sealed in a glass tube 29, Figure 3. Near one end of the tube is a pocket 30. Into the end of the tube nearest the pocket is sealed a wire 31 which extends into the pocket as illustrated, and protru'des outside of the tube at 32 as a means for making electrical connection with the mercury inside of the tube. Likewise there is another wire 33 sealed into the tube at the.

other end, which also extends into the mer cur and protrudes outside the tube at 34 for ma 'ng electrical connection with the mercury. It it obvious that if such a connector is tilted as illustrated in Figure 3, an electric current will be permitted to flow through the mercury from 32 to 34, while if the connector is tilted in the opposite direction, as illustrated in Figure 4, the mercury will break into two globules, some of it remaining in the pocket 30, thus breaking electrical contact between 32 and 34.

The connector 26, Figure 1, is fastened to a tiltable block 35 by means of .a-clamp 36. The block 35 is tiltably mounted on bearings 37 and 38 which bearings are fastened to a base plate 39 as illustrated. A hearing or hinge 40 for the pawl 16 is fastened to the block 35, Figures l and 5, so that when-the block is tilted back and forth through the proper angle, the pawl 16 will turn the ratchet wheel 18 in the direction indicated by the arrow. The magnet 24 is fastened in a fixed position to the base plate 39 by meansof a bracket 41 while an armature 42 with which the magnet reacts is fastened to the tiltable block 35. The tiltable block 35 which ture and holds the armature away from the magnet against an adjustable screw 44. The tension of the spring 43 is adjustable by means of a screw 45. The screws 44 and 45 are supported by a bracket 46 which is fastened to the base plate 39. It is obvious that when the magnet 24 is energized, it will attract the armature 42. This magnetic attraction will tilt the block including the connector 26 and the hinge 40 in one direction, while when the magnet is deenergized, the spring 43 will tilt them in the opposite direction. The tilting that is caused by the magnet is limited by an-adjusting screw 47, while the tilting back to normal position is limited by the adjusting screw 44 already referred to. It thus follows that as the magnet 24 is alternately energized and deenergized, the block 35 including the hinge 40 will oscillate and if the screws 44 and 47 are properly adjusted the awl 16 will move forward and backward t e proper distance to turn the wheel 18 through an angle equivalent to one tooth for every oscillation. I

Likewise, the connector 27 is fastened to a tiltable block 48 by means of a clamp 49. The block 48 is tiltably mounted on bearings 38 and 94 which bearings are fastened to the base plate 39. A hearing or hinge 50 for the pawl 17 is fastened to the block 48, Figures 1 and 6, so that when the block is tilted back and forth through the proper angle, the pawl '17 will turn the ratchet wheel 19 in the direction indicated by the arrow. The magnet 25 is fastened in a fined position to the base plate .39 by means of a bracket 51, while an armature 52, with which the magnet reacts, is fastened to the tiltable block 48. The tiltable block 48 which includes the hinge 50, the connector 27, and the armature 52, is held in its normal position by a spring 53 which is fastened to the armature and',holds the armature away from the magnet against an adjustable screw 54. The tension of the spring is adjustable byme'ans of a'screw 55. The screws 54 and 55 are supported by a bracket 56 which is fastened to the base plate 39. It

is obvious that when the magnet 25 is energized, it will attract the armature 52. This magnetic attraction will tilt the block 48, including the connector 27, and the hinge 50 in one direction, while when the -magnet is deenergized, the spring 53 will tilt them in the opposite direction. The tilting that is caused by the magnet is limited by an adjusting screw 57, while the tilting back to normal position is limited. by the adjusting screw 54 already referred t6. It thus follows that as the magnet 25 'is alternately energized and deenergized, the block 48, including the hinge 50 will oscillate, and if the screws 54 and 57 are properly adjusted, the pawl 17 will move includes the hinge 40, the connector 26 andv backward and forward the proper distance to the armature 42 is held in its normal position by a spring 43 which is fastened to the armaturn the wheel 19 through an angle equivalent to one tooth for every oscillation.

Both the connectors 26 and 27 are so placed on their respective blocks that when either of them is held in its normal position by its respective spring, the mercury in the connector will be unbroken and the circuit through it will be closed, while if either of the connectors is tilted by its magnet, then the mercury in the connector will be broken and the circuit through it will be open.

The magnet 22 is in series with magnet 24 so that when the magnet 24 is energized, the pawl 17 will be lifted away from the ratchet wheel 19 thus permitting the oscillation of the pawl 16 to act against its ratchet 18 to turn the shaft 13 in the direction indicated by the arrow in Figure 5. Likewise, the magnet 25 is in series with the magnet 20 so that when the magnet 25 is energized, the pawl 16 will be lifted away from the ratchet 18 thus permitting the oscillation of pawl 17 to act against its ratchet 19 to turn the shaft 13 in the direction indicated by the arrow in Figure 6.

The galvanom'eter needle 3 is provided with an electric contact pin 58, Figures 1, 2 and 7, which, when the needle is deflected in a clockwise direction, will make electrical contact with a disc 59, and which, when the needle is deflected in a counter-clockwise direction, will make electrical contact wit-h a disc 60. Contact between the pin 58 and the disc 59, closes the circuit which includes the connector 26, the magnet 24 and the magnet 22, while contact between the pin 58 and the disc 60 closes the circuit which includes the connector 27, the magnet 25 and the magnet 20. Furthermore each of these circuits includes an electric resistance 61, which forms a very important part of this invention. The purpose oi this resistance I will presently describe.

The circuit which is closed when contact pin 58 touches the contact disc 59, starts at battery 62, passes through wire 63 to abinding post 64, from the binding post 64 through a flexible connection 65, the connector 26, and a flexible connection 66 to magnet 24, from magnet 24 through wire 67 to magnet 22, from magnet 22, through wire 68 to a binding post 69, from binding post 69 through the resistance 61 to a binding-post 70,

from binding post 70 through wire 71 to binding post 72, from the binding post 72 to the hair spring 4, from the hair spring through the needle 3 to the contact pin 58,

and when the needle touches the disc 59, back to the battery 62 through wire 73.

In like manner the circuit which is closed when the contact pin 58 touches contact disc 60, starts at battery 74, passes through wire 75 to a binding post 76, thence through a flexible connection 77, connector 27 and a flexible connection 78 to magnet 25, thence through wire 79 to magnet 20, from magnet 20 through wires 80 and 68 to the bindingpost 69, thence through the resistance 61, binding post 70 and wire 71 to binding post 72, from binding post 72 through the hair spring 4 to the needle 3, and thence, when the pin 58 touches the disc 60, through wire 81 back to the battery 74. l

The circuit which is closed when the contact pin touches the disc 59, thus energizes both the magnet 24 and the magnet 22. The magnet 22 will lift the pawl 17 away from the ratchet wheel 19, and the magnet 24 will pull the armature 42 against the screw 47. The attraction between the magnet 24 and its armature 42 thus tilts the block 35 to which the hinge 40 and the connector 26 are fastened. This tilting motion will, in the manner already stated, cause the pawl 16 to push the ratchet 18 one tooth ahead thus turning the shaft 13 in the proper direction to rotate the galvanometer proportionately in a counter-clockwise direction. Furthermore. as already stated, when the block 35 has been tilted by the magnet, the circuit through the connector 26 will be broken. This will deenergize the magnets 24 and 22, the pawl 17 will again dropidown against its ratchet, and the spring 43 will tilt the block 35 back to its normal position in which electrical connection through the connector will again be established. If the contact pin 58 still touches the contact disc 59 the above action will obviouslyrepeat itself. In other words as long as contact pin 58 touches contact disc 59, so long will the block 35 continue to oscillate. This oscillation, in the manner described, will cause the pawl 16 to rotate the ratchet wheel 18 thereby turning the galvanometer and its needle 3 in a coun-' ter-clockwise direction until contact between the pin-58 and the disc 59 has been broken, at which time the circuitthrough the magnets 24 and 22 will be open and the oscillation which turns the galvanometer will stop. i

In like manner the circuit which is closed 1 when the contact pin 58 touches the disc 60 energizes the magnets 25 and 20. The magnet 20 will lift the pawl 16 away from the ratchet 19, and the magnet 25 will pull the armature 52 against the screw 57. The attraction between the magnet 25 and its armature 52 thus tilts the block 48 to which the hinge 50 and the connector 27 are fastened. This tilting motion will, in the manner al ready stated, cause the pawl 17 to pull the ratchet 19 one tooth back thus turning the shaft 13 in the proper direction to rotate the 'galvanometer proportionately in a clockwise direction. Furthermore, as previously stated, when the block 48 has been tilted by the magnet, the circuit through the connector 27 will be broken. This will deenergize the magnets 25 and 20, the pawl 16 will again drop down against its ratchet, and the spring 53 will tilt the block 48 back to its normal Lil position in which electrical connection through the connector will again be established. If the contact pin 58 still touches the contact disc 60 the above action will repeat itself. In other words as long as the pin 58 touches the disc 60, so long will the block 48 continue to oscillate. This oscillation in the manner described will cause the pawl 17 to rotate the ratchet wheel 19 therebyturning the galvanometer in a clockwise direction until contact between the pin 58 and the disc 60 has been broken, at which time the circuit through the magnets 25- and 20 will be open and the oscillation which turns the galvanometer will stop.

The electro-motive force which deflects the needle of the galvanometer may come from any source. In this particular form of my invention, however, I propose to measure the electrical energy from a thermo-couple 82 in which case the temperature of the cou- 'ple will determine the deflection of the needle. The couple, which may be placed in any medium, the temperature of which is to be measured, is connected with the binding post 83 of the galvanometer through wire 84, and with the bindingpost 72 of the galvanometer through wire 71, resistance 61 and wire 85.

It is a well known fact that when a circuit is closed between delicate electric contacts, such as between the contact pin58 of the galvanometer needle and the disc 59 and 60, the actual amount of current that flows depends not only upon the voltage but also upon the pressure between the two contact surfaces. In other words if there is only very slight pressure between two contact surfaces, such as when they are barely touching each other, then the current assing from one to the other is also very small, while if the pressure is increased, the electric flow will also be in" creased. two contact surfaces, the greater will be the flow of current until the maximum flow between the two given surfaces is obtained. To insure sufficient flow between the contact pin 58 of the delicate galvanometer needle and either of the contact discs 59 and 60, to oscillate-the pawl 16 or the pawl 17 in the manner previously stated, I utilize the electrical resistance 61 already referred to. lVhen the,

Th greater the pressure betweenfrom the binding post 69, Figure 7, through wire 85 to the couple 82, from the couple 82 through wire 84 to binding post83, from the binding post 83 through the pivoted coil 2 of the galvanometer and thence through the hair spring 4, binding post 72 and wire 71 to binding post70. The polarity of the battery 62 is such that the drop across the resistance 61 will, in the manner just stated, cause a flow throughthepivotedooil 2 in the proper direction to force the contact pin 58 tighter against the contact disc 59. This increased pressure against the contact disc 59 increases the flow through the circuit which includes the resistance 61, and magnets 24 and 22, thereby increasing the drop across the resistance 61. This increased drop causes a still reater flow through the pivoted coil 2 there% further increasing the pressure between the pin 58 and disc 59 which in turn again increases the current flow through the magnets 24 and 22, and the resistance 61. In other words immediately that the slightest contact is made between the contact pin 58 and the disc 59, the pressure of the pin 58 against 59 will build up in the manner just stated until the magnets 24 and 22 are brought into action to rotate the galvanometer counter-clockwise in the manner previously described, this rotation continuing.

until the pin 58 has freed itself-from the disc 59.

In like manner when the circuit through .-the magnets 25 and 20 is closed by the defiecti on of the pin 58 against the disc 60, then the drop across the resistance 61 will also cause a fiow through the pivoted coil 2 of the galvanometer. The polarity of battery 74 is, however, opposite to that of battery 62 so that the drop across .the resistance will send current through the pivoted coil 2 in the proper direction to increase the force of the pin 58 against thedisc 60 until the magnets 25 and 20 are brought into action to turn the galvanometer in a clockwise direction. This action as previously described will continue until the galvanoineter has turned sufficiently in a clockwise direction to free the pin 58 from the disc 60. i

The contact discs 59 and 60 are mounted on a shaft 86 which shaft is rotatably supported by bearings'87 and 88, Figures 1 and 2. These discs are insulated from the shaft 86 by insulation pieces 89 and 90 respectively, and from each other by insulation 91. The shaft 86 to which the discsare fastened, is rotated by a clock 92 or any other motive means fastened to.a bracket 93, although the rotation of the contact discs is not essential to the satisfactory operation of my invention, the rubbing conact between the rotating discs and the pin 58 may in some cases be desirable. The wires 73 and 81, Figure 2, are electrically connected with the discs by means of brushes 95 and 96 respectively.

y still, I

It is obvious from the above description that when the temperature of the thermocouple 82 increases, the shaft 5 including the galvanometer and the pulley 9 will, in the manner stated, turn in a counter-clockwise direction until the pin 58 of the galvanometer frees itself from the contact disc 59, and when the temperature of the thermo-coupledecreases, the galvanometer and the pulley 9 will turn in a clockwise direction until the pin 58 of the galvanometer needle has freed itself from the contact disc 60. It is thus obvious that the pulley 9, Figure 2, will rotate in one direction or the other in proportion to the temperature changes of the couple, and the motion of the pulley may be transmitted to any form of indicator which passes over a properly calibrated scale on which the temperature of the medium in which the couple is located may be observed. In the particular form of this invention, as illustrated in Figure 2, I utilize a flexible wire or cord 97 one end of which is fastened to the pulley 9 and the other end to a weight 98. The weight is slidably mounted on a guide rod 99 and has fastened to it a pen or marker 100. The pen or marker rests against a calibrated chart 101 fastened to a drum 102 driven by a clock 103. It therefore follows that as the pen moves up or down in proportion to temperature change,

till autographic record of the temperature variation will be made on the clock driven chart as illustrated.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1. Inadevice ofthe class described,the combination with a rotatably mounted galvanometer, of a shaft in geared connection with the galvanometer, a ratchet fastened to the shaft, a pawl for the ratchet, electrical means for moving the pawl against the ratchet to turn the shaft in a clockwise direction, a second ratchet fastened to the shaft, a pawl for the second ratchet, electrical means for moving the second. pawl against the second ratchet to turn the shaft in a counter-clockwise direction, an electrical resistance, an electric circuit which includes the resistance and the galvanometer, a second electric circuit which includes the resistance and the first electrical means, and a third circuit whichincludes the resistance and the second electrical. means.

2. In a device of the class described, the combination with a rotatably mounted galvanometer, of an electrical resistance, a shaft in geared connection with the galvanometer, a ratchet fastened to the shaft, a second ratchet fastened to the shaft, a pawl for moving the first ratchet in one direction, a second pawl for moving the second ratchet in the opposite direction, an electro-magnet for actuating the first pawl, a second electromagnet for lifting the second pawl away from the second ratchet, a third electro-magnet for actuating the second awl, a fourth electro-magnet for lifting the rst pawl away from the first ratchet, an electrical circuit which includes the first magnet, the second magnet and the resistance, a second electric circuit which includes the third-magnet, the fourth magnet and the resistance, and a third electric circuit which includes the resistance and the galvanometer.

3. In a device of the class described, the combination with a galvanometer having an indicating needle, of an electrical contact piece with which the needle makes contact when it is deflected in one direction, a second electrical contact piece with which the needle makes contact when it is deflected in the opposite direction, a shaft in geared connection with the galvanometer,a ratchet wheel fastened to the shaft, a second ratchet wheel fastened to the shaft, a pawl for turning the first ratchet wheel in one direction, a second pawl for turning the second ratchet wheel in the opposite direction, electrical means for actuating the first pawl, a second electrical-means for actuating the second pawl, an electro-magnet for pulling the first pawl away from the first ratchet wheel, a second electro-magnet for pulling the second pawl away from the second ratchet, an electrical resistance, an electric circuit which includes the resistance and the galvanometer, a second electric circuit which includes the re sistance, the first electrical means, the needle, the first contactpiece and the second magnet, and a third electric circuit which includes the resistance, the second electric means, the needle, the second contact piece and the first magnet.

4. In a device of the class described, the combination with a rotatably mounted galvanometer, of a pawl and ratchet mechanism for turning the galvanometer in one direction, a second pawl and ratchet mechanism for turning the galvanometer in the opposite direction, an electrical resistance, an electric circuit which includes the resistance and the first mechanism, a second electric circuit which includes the resistance and the second mechanism, a battery for the first circuit, the polarity of which forces current through the resistance in a definite direction, a battery for the second circuit the polarity of which forces current through the resistance in the opposite direction, and a third circuit which" includes the resistance and the galvanometer.

5. In a device of the class described, the combination with a tiltably mounted mercury switch, of an electro-magnetfor tilting the mercury switch in one direction, means for tilting the mercury switch in the opposite direction, a second tiltably mounted mercury switch, a second electro-magnet for tilting the second mercury switch in one direction, means for tilting the second mercury switch in the opposite direction, a rotatably mounted galvanometer, a pawl and ratchet for rotating the galva'nometer in one direction said pawl being actuated by the tilting motion of the first mercury switch, and a pawl and ratchet for rotating the galvanometer in the I means for tilting the second mercury switch in the opposite direction, a rotatably mounted galvanometer, a pawl and ratchet for rotating the galvanometer in one direction said pawl being actuated by the tilting motion of the first mercury switch, a pawl and ratchet for rotating the galvanometer in the opposite direction said pawl being actuated by the tilting motion of the second mercury switch, a third electro-magnetfor pulling the first pawl away from the first ratchet, and a fourth I electro-magnet for pulling the second pawl second mercury switch, the second magnet,

away from the second ratchet.

7. In a device of the class described, the combination with a tiltably mounted mercury switch, of an electro-magnet for tilting the mercury switch in one direction, means for tilting the mercury switch in the opposite direction, a second tiltably mounted mercury switch, a second electro-magnet for tilting the second mercury switch in one direction, means for tilting the second mercury switch in the opposite direction, a rotatably mounted galvanometer having an indicating needle, an electric contact piece which the needle touches when deflected in one direction, a second electric contact piece which the needle touches when deflected in the opposite direc-' tion, a pawl and ratchet for rotating the galvanometer in one direction said pawl being actuated by the tilting motion of the first mercury switch, and a pawl-and ratchet for rotating the galvanometer in the opposite direction said pawl being actuated by the tilting motion of the second mercury switch. a third electro-magnet for pulling the first pawl away from the first ratchet, a fourth electro-magnet for pulling the second pawl away from the second ratchet, an electrical resistance, an electric circuit which includes the resistance, the first mercury switch, the first magnet, the fourth magnet, the needle and the first contact piece, a second electric circuit which includes the resistance, the

, the third magnet, the needle and the second contact piece, and a'third circuit which includes the galvanometer and the resistance.

8. In a device of the class described, the combination with a tiltably mounted mercury switch, of an electro-magnet fontilting the.

mercury switch in one direction, means for tilting the mercury switch in theopposite direction, a second tiltably mounted'mercury switch, a second electro-magnet for tilting the second mercury switch in one direction, means for tilting the second mercury switch in the opposite direction, a rotatably mounted galvanometer, a pawl and ratchet for rotating the galvanometer in one direction said pawl being actuated by the tilting motion of the first mercury switch, a pawl and ratchet for rotating the galvanometer in the opposite direction said pawl being actuated by the with the proper polarityto cause a currentflow through the resistance in a predetermined direction, and a battery in the second circuit to cause a current flow through the resistance in the opposite direction.

9. In a device of the class described. the combination with a tiltable support, of an elcctro-magnet for tiltingthe support in one direction, a spring for tilting the support in the opposite direction, a switch which is opened by the tilting effect of the magnet and closed by the tilting effect of the spring, a rotatably mounted galvanometer with an indicating needle, a pawl and ratchet. for rotating the galvanometer in one direction, one end of the pawl being pivoted on the tiltable support, a second tiltable support, a second clectro-magnet for tilting the second support in one direction, a second spring for tilting the second support in the opposite direction, a second switch which is opened by the tilting effect of the second magnet and closed by the tilting effect of the second spring, a second pawl and ratchet for rotating the galvanomcter in the opposite direction, one end of the second pawl being pivoted on the second tilta-' ble support, a third electro-magnet for pulling the firstpawl away from its ratchet, a fourth electro-magnet for pulling the second pawl away from its ratchet. a contact piece with which the needle of the galvanometer makes contact when it is deflected in one direction, a second electrical contact piece with which the needle makes contact when it is deflected in the opposite direction, an electrical resistance, an electric circuit which includes the resistance and the galvanometer, a second electric .circuit which includes the resistance, the needle, the first contact piece, the first magnet, the first switch and the fourth magnet, and a third electric circuit which includes the resistance, the needle, the second contact piece, the second magnet, the second switchand the third magnet.

p 10., In a device of the class described, the combination with a tiltable support, of an electro-magnet for tilting the support in one direction, a spring for tilting the support in the opposite direction, a switch which is open ed by the tilting effect of the magnet and closed by the tilting effect of the spring, a rotatably mounted galvanom'eter with an indicating needle, a pawl and ratchet for rota-ting the galvanometer in one direction, one end of the pawl being pivoted on the tiltable support, a. second tiltable support, a second electro-magnetfor tilting the second support in one direction, a second spring for tilting the second support in the opposite direction, a second switch which is opened by the tilting effect of the second magnet and closed by the tilting effect of the second spring, a second pawl and ratchet for rotating the galvanometer in the opposite direction, one end of the second pawl being pivoted on the second tiltable support, a third electro-magnet for pulling the first pawl away from its ratchet, a fourth electro-magnet for pulling the second pawl away from its ratchet. a contact piece with which the needle of the galvanometer makes contact when it is deflected in one direction, a second electrical contact piece with which the needle makes contact when it is deflected in the opposite direction, an electrical resistance, an electric circuit which includes the resistance and the galvanometer, a second electric circuit which includes the resistance, the needle, the firstcontact piece, the first magnet, the first switch and the fourth magnet, a third electric circuit which includes the resistance, the needle, the second contact piece, the second magnet, the second switch and the third magnet, a battery for forcing an electric current through the second circuit, a battery of opposite polarity for forcing electric current through the third circuit, and means for imparting motion to the contact pieces.

11. In a device of the class described, the combination with a galvanometer consisting of a permanent magnet, between the poles of which is pivoted a coil, the torque of which coil reacts against a hair spring, an'indicating needle fastened to the coil, a tiltable frame, an electro-magnet for tilting the frame in one direction, a spring for tilting the frame in the opposite direction, a switch which is opened by the frame when tilted by the magnet and closed when tilted by the spring, a pawl and ratchet for rotating the galvanometer inone direction, one end of the pawl being hinged on the tiltable frame, a second tiltable frame, a second electro-magnet for tilting the second frame in one direction, a second spring for tilting the-second frame in the opposite direction, a second switch which is opened by the frame when tilted by the second magnet and closed when tilted by the second spring, a second pawl and electrical contact when it deflects in the opposite direction, an electric circuit which includes the coil and hair spring of the galvanometer, a second electric circuit which includes the hair spring of the galvanometer, the indicating needle, the first contact piece the first electro-magnet, the first switch and the fourth electro-magnet, a third electric circuit which includes the hair spring of the galvanometer, the indicating needle, the second electro-magnet, the second switch and the third electro-magnet, and means for measuring the angle through which the galvanometer is rotated.

12. In a device of the class described, the combination with the pivoted coil of a galvanometer, of a hair spring for resisting the motion of the coil, an indicating needle for measuring the motion of the coil, an electric circuit which includes the coil and the hair spring, means for rotating the coil in one direction independently of the current pass ing through the coil, similar means for rotating the coil in the opposite direction, an electrical means for operating thefirst rotating means, a second electric means for operating the second rotating means, a contact piece with which the needle makes electrical contact when deflected in one direction, a second contact piece with which the needle makes electrical contact when deflected in the opposite direction, a second electric circuit which includes the needle, the hair spring, the first contact piece and the first electrical means, and a third electric circuit which includes the hair spring, the needle, the second contact piece, and the second electrical means.

FRITZ FREDERICK UEHLING.

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