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Oct. 29, '1946. L. F. BEACH 2,410,039 MAGNETIC FIELD ,RESPONSIVE DEVICE Filed July 31, 1941 ‘ \COMMUTATOR 2 Sheets-Sheet l > AMPLIFIER TO OR INDICATOR CONTROL INVENTOR ‘ , CIRCUIT LENNOX F‘ BEACH - HIS. ATTORNE . Oct. 29, 1946. L. F. BEACH ' 2,410,039 MAGNETIC FIELD RESPONSIVE DEVICE Filed July 51, 1941 2 Sheets-Sheet 2 ‘FIE-.5 H 5.53 MOTOR 2-POLE v ALTERNATO ' / 843 4-—POLE ALTERNATOR INVENTORS LENNOX F. BEACH , Patented Oct. 29, 1946 2,410,039 UNITED STATES PATENT‘ OFFICE MAGNETIC FIELD‘ RESPONSIVE DEVICE Lennox F. Beach, Merrick, N. Y., assignor to The Purves Corporation, Spring?eld, Mass, a cor poration of Massachusetts Application July 31, 1941, Serial No. 404,809 13 Claims. (Cl. 175-183) 1 2 This invention relates to magnetic ?eld‘ re The primary windings may be energized by any periodically varying current and arev illustrated? as being energized by alternating current from] secondary winding i3 of power transformer T5 sponsive devices, especially of the type‘ shown‘ in Patent No.'2,047,609, issued July 14, 1936, to Haig Antranikian. As‘ therein explained, such devices operate on the principle of a- magnetic core whose reluctance is periodically varied by a periodically varying energizing magnetomotive force and which will respond to ?xed or varying external magnetomotive forces to yield.- a periodic output current or voltage whose phase‘ will correspond to the polarity or direction of the external mag netomotive force, and whose magnitude will cor respond to the instantaneous intensity ‘of the whose primary i7 is connected to any suitable source of alternating current. It is to- be under stood that the terminals of winding 5‘, 1 may be connected to’ any source of periodically varying voltage. Secondary II‘ and primaries 5', ‘I are $0 arranged that, in the absence of any‘ external’ . magnetic ?eld components along core 3 (aswherr the core points East and West if the earth’s magi-i netic ?eld is used‘), no voltage is induced in sec-> onclary M. This adjustment may be‘ performed’ The present invention is concerned with im 15 by making coil ll slidable along 0011's 5, 1, provements on the type of device shown in the A suitable construction‘ for this‘ pick-up device above patent, and‘ adaptations of this improved is shown in my copending application Serial No. device to uses such as magnetic ?eld direction 348,582 for Direction indicator for magnetic magnetomotive force. . and/or sense indicators, magnetic ?eld intensity ?elds, ?led July 30; 1940, and which matured-on indicators, and magnetic ?eld responsive de 20 August 28, 1945- into U. S. Patent No. 2,383,459. vices. Alternatively, core l maybe formed in two sep It is accordingly an object of the present in~ vention to provide an’ improved‘ indicator for the direction and/or sense of a magnetic ?eld such arate but adjacent sections, each section having as the earth's ?eld. being, series-connected, to provide a voltage thereacross which is produced through interac It is another object of this invention to pro vide an improved device for determining the in stantaneous intensity of a ?xed or varying mag netic ?eld. ‘ ' a primary‘ winding such as 5 or 1 and half of the secondary winding» H, the two secondary halves tion between the device and the external ?eld, the primary windings being preferably series connected. It is a further object of this invention to pro 30 One terminal !2 of secondary H’ is connected vide an improved relay device responsive to a to one side of direct zero-center meter l9 whose magnetic ?eld. Other objects and advantages will; become ap parent from the speci?cation, taken in connec tion with. the accompanying drawings wherein the invention is embodied in concrete form. In the drawings, Figs. 1 to 3 are schematic diagrams of devices for indicating the direction and intensity of magnetic ?elds; Fig. 4 is‘a schematic diagram of a relay device responsive to magnetic ?elds; other terminal is connected to the junction 22 of two series connected recti?ers 2|. These rec ti?ers may be of any desired type, such as chem ical, electrical, etc. The recti?ers 2'! are con: nected in series across another secondary’ 23. of supplytransformer [5. When a different source of periodically varying voltage is used, the ter-. minals of recti?ers 2! may be connected directly. thereacross. . . Also connected across this secondary23 is a potentiometer resistor 25,. whose variable arm 2.‘! is connected to the other terminal ll! of pick-up of Figs. 1 to‘ 3; and, ._ secondary ll. Arm 21 is adjusted so that its. po Fig. '7 is. a schematic diagram, of‘ a. magnetic 45 tential is the same asthat of the junction 22 of ‘Figs. 5.and‘6 are modi?cations of the devices. ?eld intensity measuring device. Fig. 1 shows a device for indicating the orien recti?ers 2!- “ tation and instantaneous intensity of a ?xed or When. core, 3 is unaffected by external mag netic ?elds, it will be symmerically and periodi varying magnetic ?eld. A magnetic pick-up de cally magnetized in opposite directions by the vice i has a core'3 upon which are wound iden 50 alternating current in the primary windings: 5; ‘l, the current magnitude being adjusted to op tical primary coils 5, ‘I. These coils are con erate the core with varying permeability andre nected in series, as at 9, and are wound so as to luctance. If the core is subjected to an external create opposing magnetomotive forces and ?uxes in core 3., Also, wound on core 3- and' preferably concentric9 with coils 5, ‘I is‘ a, secondary coil ll. magnetic ?eld. for instance the earth’sv ?eld, then, as the primary current passes through zero‘, 2,410,039 4 there will be a time displacement of the point of zero magnetism. There will be a resulting time interval between the instants that the right and external magnetic ?eld (right or left) with re spect to the axis of core 3. Since the intensity of the external ?eld determines the Voltage picked left portions of the core pass through zero mag netism. This time interval will increase as the up by secondary II, meter I9 may be calibrated in magnetic ?eld units to read directly the in tensity and polarity of the component of the ex strength of the external ?eld is increased. This e?ect produces an alternating voltage in the secondary winding II having a component of ternal magnetic ?eld along the axis of core 3. If the only external ?eld is the earth’s ?eld, this device will indicate the component of the earth’s double the frequency of the "primary current. Reversal of the direction of the external magnetic 10 ?eld along the axis of core 3. Meter I9 maybe calibrated directly in degrees of magnetic bear ?eld will produce phase reversal of the secondary voltage. V ing, permitting the use of the device as a magnetic » In other words, the exciting coils 5 and ‘I, when compass. ' Itis found that the absolute magnitude of the energized from a suitable source of alternating ' output voltage from secondary winding II de pends upon the relative phase of the current in ,the primary coils with respect to the voltage or pulsating current, will produce periodically varying ?uxes in the core 3 of permeable mag netic material. ' The number of ampere turns will determine the degree of saturation produced across recti?ers 2I. A condenser 29 is therefore used to adjust this phase relation to an optimum along its magnetization curve. Therefore, the 20 value. This condenser may be variable, and is ad amount of current supplied to these exciting justed by noting maximum indication on meter windings or coils having a given number of turns I9 for a given external ?eld. . will determine the desired degree of saturation It is not necessary to use center~tapped re of the core. The periodically varying ?uxes pro sistor 25. The connection to point 2‘! may be duced in the core by the coils 5 and ‘i will be in 25 made directly to a center-tap on secondary wind bucking relationship due to the arrangement of ing 23. Also, the two separate secondary wind these coils and if the secondary or pick-up wind ings 23 and I3 may be combined‘into one, with ing “is properly adjusted in symmetrical rela the energizing circuit for coils 5, ‘I and the recti tion to these ?uxes, no voltage of fundamental fier circuit connected in parallel thereto. Fur frequency or of the frequency of the source of en 30 thermore, the present connection to point 21 may ergy used in exciting the core will appear in the be made to the junction 9 of coils 5 and ‘I, thereby in the core or the zone of operation of the core pick-up winding. In this invention, it will be ob served that the coil Il may be adjustedaxially reducing the number of wires to the pick-up unit I, which may be, and usually is, located at a dis of the core 3 to effectively balance out this funda tance from the indicator meter I9. ' mental frequency voltage. However, when the 35 Fig. 2 shows a modi?cation of the device of core is subjected to an external unidirectional Fig. 1. Here the pick-up unit primary windings ?eld, unidirectional fluxes are induced in the core 5, ‘I are energized from a two-pole alternator 2V9 , 3 thereby rendering the wave form of the voltage driven at constant speed by motor 3!. Switching induced in let us say one Pick~up winding of an is effected by commutator 33, which has two ?xed unsymmetrical character. This is due to the fact 40 90° segments 35, 31 and a movable shorting arm that a double frequency component is present in the induced voltage and it is the double fre quency component, the fundamental being bucked out, which is supplied to the indicating 39 rotated by motor 3| in synchronism with al ternator 29. Arm 39 connects segments 35, 31 for 90 degrees of rotation of alternator 29, opens the circuit for the succeeding 90 degrees, and re means as a measure of the strength of the uni 4: peats this cycle. Since alternator 29 will gen directional ?eld along the longitudinal axis of erate one cycle per revolution, commutator 33, the core. ' which isconnected in series with secondary wind Meter I9 is of the direct current zero-center ing II and zero center meter I9, will close the sec type and is used to indicate the direction and in ondary circuit for alternate quarter cycles orthe tensity of the external ?eld. For this purpose, primary current, which correspond to alternate recti?ers 2| are used to block off the current of half-cycles of secondary current, which has a secondary winding I I during half-cycles of the frequency double that of the primary current. supply voltage fed from winding 23 having a By properly phasing the commutating action with given polarity and to permit passage of second respect to the alternator voltage output, as by ary current only during the half-cycles of op shifting arm 39 relative to shaft 43, the commu posite polarity. ' tator 33 is adjusted to effect mechanical recti Thus, let it be assumed that recti?ers 2| will conduct only when their upper terminals are posi tive with respect to their lower terminals. Dur ing the half-cycle of voltage from supply second ?cation of the secondary current, and direct cur rent meter I9 will indicate the sense of the devi ation of the coil axis from the axis of the external ?eld, by its right or left de?ection, and the amount of such deviation, by the amount of de ary 23 that these recti?ers are conducting, a cur rent from secondary II will flow through meter ?ection. . - ' ' I9 and through one or the other of the recti?ers, depending on the polarity of this current from winding I I. It will produce de?ection of the in dicator of meter I9 in a direction corresponding It is obvious that the primary coils 5, ‘I "of Fig. 2 might as well be energized from any source of periodically varying current, so long as the com mutator 33 is properly synchronized with the fre to its polarity. During the succeeding half-cycle of supply voltage from Winding 23, both recti quency of the source, so as to provide proper in ?ers .2I are'maintained non-conductive by the voltage of winding 23, since this voltage is much larger than the voltage across secondary winding I I, so that no current can ?ow through the meter I9. The meter I9 is thereby supplied with cur rent of predominantly one polarity and that po the secondary current. Fig. 3 shows a pulsating current supplied to primary windings 5, ‘I by means of vibrator 45 having coil 4'! and armature 49. Current from battery 55 energizes coil 41 and draws up arma larity corresponds to the relative direction of the terruption and phase-sensitive recti?cation of '70 ture 49 against the opposition of spring 51. Con tacts 5| are thereby closed and short circuit coil 2,410,039 5 6 41, permitting spring 51 to withdraw armature 49, and open contacts 5|, whereupon the cycle of operations is repeated. the anodes energized directly from secondary‘ 23 of supply transformer ‘I5. A center-tapped choke coil may be used in place of resistor ‘II. A suit Contacts 53 are opened and closed‘ in syn ' able bias may be inserted‘between the cathodes chronism with the operation of armature A9,. and oftube 69‘ and the center-tap of resistor ‘II, or its choke equivalent if it is desired to make the de serve to open or close the circuit of meter lBg. The pulsating current supplied to primary , vice. responsive only above a predetermined sig coils 5, ‘I creates a double frequency current in nal level. v _ I secondary I I, in the presence of an external mag» Fig. 6 shows another modi?cation of the device netic ?eld, as in Figs. 1 and 2. The secondary 10 in which all Switching means are eliminated. current is connected. to meter I9, in series with Motor 3! drives two-pole. alternator 29 and four interrupter contacts, 53, an ampli?er 59 being, in pole alternator I253. The voltage generated by the serted if necessary. two-pole alternator energizes primary windings » The phase of the primary current pulsations 5, ‘I. The double frequency output from second relative to. the interruption of contacts 5i is ad 15 ary coil I I is fed to one coil, for example the mov justed‘by adjustingv the capacitance of condenser ing coil 19, of dynamometer-type meter 8 I, whose BI, to yield maximum secondary current for ?xed second, or ?xed winding 83 is energized from the double frequency output of four-pole alternator external ?eld. Once adjusted, condenser 6| re I29. Meter 8i will indicate the relative magni mains ?xed in value. Condenser 63 minimizes sparking at contacts 53. 20 tude of the output voltages from alternator I29 Meter I9 will then give right or left indications and secondary winding II. Also, the meter indi according to the sense of the external ?eld, and in amount according to the'intensity of the ex ternal ?eld component along the axis of the coil. Ampli?er 59 can be biased in known ways to pre vent any output until a certain predetermined input level is attained. In this way undesirable two alternators is’ adjusted, either by adjusting their relative ‘armature positions or by inserting small random ?uctuations have no effect on meter an adjustable condenser in circuit with one of cation will reverse direction when the phase of the voltage output from secondary winding VII reverses. ' 1 , , The phase relation between the outputs of the them, to give a maximum de?ection on meter 8| I9. Fig. 4 shows a further modi?cation of the de 30 for ?xed position of the core 3 and ?xed magni vices of Figs. 1 to 3, used as a magnetic ?eld in tude of external ?eld. Fig. 7‘ shows an adaptation of the special trans dicator. In this ?gure, the output of secondary winding I I_ is fed to an ampli?er 59, whose output former of Figs. 1 to 6 for use as an instrument for measuring the magneto-motive force and in energizes the coil of relay 65. The contacts of relay 65 may control any type of outside indica tensity of an external ?eld. In addition to wind ings 5, ‘i, ll on core 3, an additional winding 85 tor or control circuit. This device will respond is placed symmetrically with respect to the re to the approach or passage of iron or magnetic maining windings. An adjustable amount of di bodies, such as automobiles, trains, or parts on a conveyor. The relay output may operate stop rect current is passed through this winding 85 lights on a highway, or a counter. from battery 53, the polarity and magnitude‘ of The sensitiv- , ity of the device can readily be adjusted so as not to respond to a disturbance below a certain ‘mini mum value, and to record a strong signal as soon as the disturbance exceeds this minimum, as by proper bias on the input of ampli?er 59. Fig. 5 shows a further modi?cation of Figs. 1 to 3. Here the voltage across the secondary wind ing II may be tuned to double the supply ire~ quency as by condenser 6'1. The secondary wind ing I I may be as tuned in any of the modi?cations the current being adjusted by potentiometer 9|, _ and indicated on direct current meter 89. Coils 5, ‘I are provided with periodically varying cur rent from source I‘! as in the other modi?cations. CA r. of this invention. This secondary voltage is then applied to the control grids of twin triode 69 by way of center-tapped input resistor 'II whose cen ter-tap is connected to the cathodes of tube 69. The anodes of tube 69 are energized with pulsat ing voltage from secondary winding 23 by way of recti?er bridge '53 and equal load resistors 15. Preferably, the double frequency, alternating With zero direct current in coil '85, alternating current meter ill will yield an indication of any external ?eld. Potentiometer 9! is then adjusted until meter 81 registers zero value. Then it will be clear that the external ?eld is exactlyibal anced by the ‘?eld produced by current in coil 85. Knowing the number of turns in coil 85, and reading the current on meter, 89 will give im mediately the magnetomotive force (ampere turns) corresponding to the external ?eld. This is also an indication of the external ?eld strength and meter 88 may be calibrated. to read ?eld strength at once. The polarity of current regis tered by meter 89 will also indicate the direction current ripple from the recti?er ‘i3 is used as the of the external ?eld. ’ plate potential for the plates or anodes of tube Of course, any of the indicating systems shown G O in Figs. 1 to 6 may be used in place of meter 81. 69. Meter ‘I1 is connected across resistors '55, as shown. With zero voltage input, both sections of As many changes could be made in the above tube 69 are adjusted to take equal plate current, construction and many apparently widely differ so that zero voltage will appear across meter 'i'i. ent embodiments of this invention could be made When secondary II produces voltage, it will act without departing from the scope thereof, it is differentially on the two sections of tube 69, re intended that all matter contained in the above sulting in a net voltage across meter ll, whose description or shown in the accompanying draw polarity depends on the phase of the input volt ings shall be interpreted as illustrative, and not in age from secondary winding I I. Tube 69 acts as a a limiting sense. , ' ' phase discriminating device as well as an ampli What is claimed is: 70 ?er. The indication on meter 7'! will then indi l. A device as in claim 9, in which said indi cate both magnitude and direction of the external ?eld. ’ It is obvious that a duplex tube need not be used, as two separate tubes would perform in the same way. Also recti?er T3 may be omitted and 75 cating means includes an indicator and means for rendering said indicator ineffective during alter nate half-cycles of said periodically varying mag netomotive forces. ‘ ‘ - 2,410,039 7 8 2.‘ A device as in claim 9, in which said indicat ing means includes an indicator, and means syn is the mean of the potentials across ‘the energy chronized with said varying magnetomotive forces 8. In a device sensitive to an external, unidirec for rendering said indicator ineifective during alternate half-cyles'of said varying magnetomo tional magnetic ?eld for supplying a signal voltage output dependent in magnitude uponthe tive forces’. 3. .A magnetic ?eld responsive device compris direction of said ?eld relative thereto, a‘ core of permeable magnetic material, means including a ing a core of magnetic, permeable material, means including a source of periodically varying elec source of periodically varying electrical energy for producing periodically varying ?uxes in a source for said recti?ers. ' , trical energy for producing periodically varying 10 zone of said core and in opposed bucking rela ?uxes in a zone of said core and in opposed buck ing relationship, a pick-up coil associated with tionship, a pick-up coil associated with said ‘core in said zone thereof and positioned in symmetrical said zone of the core and symmetrically positioned with respect to said ?uxes, means for indicating relation to said bucking ?uxes, interactionbe tween said device and said external ?eld produc the output from said coil, and phase-sensitive 15 ing a periodically varying voltage in, said pick-up means connected with’said energy source for sup plying a unidirectional current from said coil output to said indicating means. I coil, and means forv rectifying ‘the output oflfsaid coil, said rectifying means being connected .to and controlled by said energy’ source whereby‘ to 4. A magnetic ?eld responsive device com render the polarity sense of the recti?ed coiloute prising a core of magnetic, permeable material, 20 put dependent upon the phase relationship of the means including a source of periodically varying coil output with respect to said energy source.‘ electrical energy for producing periodically vary 9. In a device sensitive to an external, unidirec'f ing ?uxes in a zone of said core and in opposed tional magnetic ?eld for supplying a signal voltage bucking relationship, a pick-up coil associated output dependent in magnitude upon the direc with said zone of the core and symmetrically 25 tion of said ?eld relative thereto, a core of per positioned with’respect to said ?uxes, meansfor indicating the output from said coil, electron tube means connected to receive the output of said coil and to supply current to said indicating meable magnetic material, means including a source of periodically varying electrical energy for producing periodically varying ?uxes Yin'a zone of said core and in opposed bucking rela means, and means for supplying a potential to 30 tionship, a pick-up coil associated with said core in said zone thereof and positioned in symmetrical the plate of said tube means of a frequency sub stantially twice that of said source. 1 5. In a‘devicesensitive to an external, unidi~ - rectional magnetic ?eld for supplying a signal relation to said bucking ?uxes, interaction be tween said device and said external ?eld 'produc4 ing a, periodically varying voltage in said pick-up voltage output dependent in magnitude upon the 35 coil, means for rectifying the output of said coil, and indicating means connected to said recti?er direction of said ?eld relative thereto, a core of permeable magnetic material, a pair of exciting means for indicating the relative phase and mag coils surrounding said core, a source of periodi nitude of the coil output, said rectifying means cally varying electrical energy of fundamental being connected to and controlled by said energy source whereby to provide said indicating means frequency for said coils, said coils being arranged vto produce opposed and bucking exciting ?uxes in said core, a pick-up coil associated with said core and so positioned as substantially to buck out any ‘ with 10. phase In a sensitive device sensitive indications. to an external, uni , voltages induced therein by said exciting ?uxes directional magnetic ?eld for supplying a signal voltage output dependent in magnitude upon the but to supply a doubleffrequency voltage output through interaction with the external ?eld, means direction of said ?eld relative thereto, a core of permeable magnetic material, means including a for indicating the output from said coil, and source of periodically varying electrical energy for producing periodically varying ?uxes in a zone of said core and in opposed bucking relationship‘, a pick-up coil associated with said corein said zone thereof and positioned in symmetrical rela tion to said bucking ?uxes, interaction between means controlled by said energy source for sub jecting said indicating means to unidirectional current from said pick-up coil. 6. In a device sensitive to an external, uni directional magnetic ?eld for supplying a signal voltage output dependent in magnitude upon the said device and said external ?eld producing a periodically varying voltage in said pick-up coil, direction of said ?eld relative thereto, a core of magnetic, permeable material, means including a 55 electron tube means having a control electrode source of periodically varying electrical energy thereof connected to receive the output of said coil, and means for supplying a potential to the for producing periodically varying ?uxes in a zone plate of said tube means of substantially the same of said core and in opposed bucking relationship, frequency as the frequency of the voltage applied a pick-up coil associated with said zone of the core and symmetrically positioned with respect 60 to the control electrode thereof. 11. A magnetic ?eld responsive device com to. said ?uxes, a zero-center reading meter for prising a core of magnetic, permeable material, indicating the magnitude and direction of the means including a source of periodically varying output of said pick-up coil, and means controlled electrical energy'for producing periodically vary by said energy source for subjecting said meter ing ?uxes in a zone of said core and in opposed to unidirectional current from said pick-up coil, bucking relationship, a pick-up coil associated the direction of said current being dependent with said zone of the core and symmetrically posi upon the phase relationship of the pick-up coil tioned with respect to said ?uxes, means for indi output with respect to said energy source. cating the output from said coil,> electron tube 7. A device of the character recited in claim 9, means connected to receive the output of said in which the indicating means includes an indi cator and two series-connected recti?ers ener gized from said energy source, said indicator and pick-up coil being connected between the junc tion of said recti?ers and a point whose potential 75 coil and to supply current to said indicating means, and frequency doubling means connected with said energy source for supplying a reference potential to the plate of said tube. ' ' ' 12. A device of, the character recited in claim 11 2,410,039 10 in which the frequency doubling means com prises a recti?er. bucking relationship, a, pick-up coil associated with said core in said zone thereof and positioned 13. In a compass device sensitive to an ex in symmetrical relation to said bucking ?uxes, ternal, unidirectional magnetic ?eld for supply ing a signal voltage output dependent in magni interaction between said device and said external ?eld producing a periodically varying voltage in said pick-up coil, and means controlled by said energy source for rectifying the output of said tude upon the direction of said ?eld relative thereto, a core of magnetic permeable material, means including a source of periodically varying electrical energy for producing periodically vary ing ?uxes in a zone of said core and in opposed 10 pick-up coil. LENNOX F. BEACH.