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Dec. 17, 1946. H. JENKINS , 2,412,617 SYSTEM OF COMPASS COMPENSATION Filed Aug. 24, 1942 2 Sheets-Sheet 1 5444 INVENTOR HOWARD JENKINS Dec, 17, 1946. H_ JENKINS 2,412,617 SYSTEM 01;‘ COMPASS COMPENSATION Fliled Aug. 24, 1942 2 Sheets-Sheet‘2 FIG‘. 4 30 40 T "In" hum“ __ |I|,._ L _ ‘ llk'lll W‘". 6 ~ I . [28 j L - Q “I 50 J Q1 1 [lo 1 'i i|l “ 27‘- _\ ML Q Q ' 26 25 ‘ ‘ii ' INVENTOR BY‘ HOWARD JEN/(IN //A "Mi TT NEY Patented Dec. 17, 1946 2,412,617 ‘UNITED STATES PATENT OFFICE 2,412,617 SYSTEM OF COMPASS COMPENSATION Howard Jenkins, Arlington, Va. Application August 24, 1942, Serial No. 455,910 10 Claims. (01. 33-225) (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. ‘757) i. This invention relates to magnetic compasses and in particular to a system of compensating magnetic compasses for errors induced by the degausslng circuits utilized for protection against magnetic mines. it is the present general practice to install large tion produced by the subpermanent magnetism of the vessel. Since different degausslng coils are installed in different locations on the ship and are operated separately for di?'erent conditions for heading and latitude, the resultant magnetic ?eld at the coils of wire on the forward and after portions binnacle which is produced by this degausslng of a vessel passing through enemy waters and flux may be considered separately for each coil. to provide means for passing electric current The ?eld from any individual degausslng coil will through the coils for the purpose of neutraliz 10 vary proportionally with the excitation of the ing the magnetic ?eld set up by said vessel as a. degausslng coil and its direction will completely protection against magnetic submerged mines. reverse with changes in the coil polarity. Thus, tSuch procedure is referred to as degausslng and by utilizing compensating or corrector coils lo the coils employed by this process are called. de cated at the binnacle and connecting each com gaussing coils, the ‘forward coil being referred 15 pensating coil in circuit with its respective de~ to as the F coil and the after coil being referred gaussing coil, the current in the compensating to as the Q coil. In addition to .the F and Q coils may be maintained at a, ?xed ratio Wtih coils, a third coil referred to as the M coil is also the current in the degaussing coil. employed to neutralize the magnetic ?eld of said It is, therefore, an object of this invention to vessel. Other coils or combinations of coils, in 20 automatically compensate for the degaussing field cluding an S and A coil, are also used. In some by establishing at the binnacle, a separate mag instances lack of material has necessitated the netic ?eld for each separate degausslng circuit, installation of a single M coil. and to cause the ?eld to vary in direction and As is well known, a steel vessel has a magnetic intensity in a ?xed ratio with changes in direc character of its own which includes the subper 25 tion and magnitude of the current in said de manent magnetism created in building the ves gaussing circuit so that the said separate field sel and the transient magnetism induced in the will at all times equal the ?eld intensity of its vessel by the earth’s magnetic ?eld. To render respective degaussing circuit at the center of the such a steel vessel magnetically neutral at all binnacle and will oppose its direction. times, as is desirable in the degaussing operation, 30 It is a further object of this invention to ar it is necessary to adjust the current through the range about the binnacle three compensating degaussihg coils to a particular predetermined windings for each effective degaussing circuit value which varies with changes in the vessel's with the axes of the windings mutually disposed head and with changes in latitude. at 90” so that the ?eld produced by each wind The degausslng circuits of the vessels induce 35 ing may-be vectorially combined to produce a a magnetic ?eld at the binnacles, similar to the resultant ?eld equal in magnitude but opposite ?eld produced by the vessel’s subpermanent mag in sense to the magnetic ?eld through the cen netism in that the compass deviation caused by ter of the binnacle produced by the respective the presence of this ?eld would be essentially degausslng circuits from which the said wind semicircular if the ?eld were not varied in in~ 40 ings are energized. tensity and direction. The effect of the degauss Other objects and many of the attendant ad ing ?eld upon the magnetic compass is in other vantages of this invention will be appreciated as respects dissimilar to the compass deviation the same become better understood by referring caused by the subpermanent magnetic ?eld of the to the following detailed description when con vessel. For example, large heeling errors are pro~ 4:5 sidered in connection with the accompanying duced by the degausslng ?elds. Furthermore, sheets of drawings wherein: the total effect of the degausslng ?eld is electro Fig. 1 illustrates diagrammatically an arrange magnetic in nature; that is, the magnitude and ment of the degaussing coils and the circuit con direction of this ?eld change as the current mag nection leading therefrom to their respective nitude and'direction through the separate coils 50 compensation coils; _ is adjusted or changed for different headings and. Fig. 2 is a perspective view of the degausslng for di?erent latitudes. Compensation for the coils and the resultant ?eld at the center of the degaussing field cannot therefore be easily ac compass produced by the degausslng circuit to ' complished by the utilization of permanent mag gether with its three vector components; nets as is the case with the semicircular devia 65 Fig. 3 is a plan view of the Navy standard bin ‘ 2,412,617 4 nacle showing the prefered position of the hori zontal compensating coils; - Fig. 4 an elevational view of the binnacle of Fig. 3 showing also a preferred arrangement of the vertical compensating coils; and Fla-5 is an elevational view of ‘the binnacle provided with a dip needle utilized in compensat ing for the vertical component of the degaussing ?eld. . > ‘ Referring now to the drawings on which like numerals of reference are employed to designate like parts through the several views and in par . produced by the M coil will have a magnitude and direction at the center of the- compass 20 equal to the vector D6 of Fig. 2. To compensate for this ?eld there is established along each of the three components V, H. and Hp, a ?eld of an intensity equal to the vectors V, H; and Hp, respectively, but of a direction opposite thereto. The three coils 30, 40 and 50 of Fig. 1 are each placed so that their axes coincide with a differ l0 ent vector component. More speci?cally. the axis of the coil 50 is vertically arranged relative to the vessel and is positioned relative to the bin ticular to Fig. 2 thereof, there is shown thereon . nacle so that it passes through its center. The axes of coils 30 and 40 are each coplanarzwith a vessel, such as a freighter or transport, indi cated generally by reference numeral ill and pro-v 15 the axis 01‘ the magnetic members of the com pass and are arranged relative to the binnacle vided with a degaussing coil F within the for with the axis of each on adjacent intercardinal ward part of the vessel and a degaussing coil compass points when the ship’s heading is mag Q within the after part of the vessel. A degauss netic north or south. Each coil is provided with ing coil M is also provided which, as illustrated, completely .follows the general outline of the 20 a plurality of separate individual and coaxial windings one for each effective degaussing cir vessel. The vector DG is drawn from the cen cuit, to provide a means for establishing for each ter of the compass 20 to illustrate that the mag separate degaussing circuit three separate vector netic ?eld produced by any one or all of the coils component windings positioned along each ordi M, F, or Q, has a magnitude and direction at _ this point equal to the vector DG. It is this ?eld 25 nate so that the magnitude of each vector com ponent can be ‘made to follow directly the vari which produces the compass deviations referred ations in the current magnitude of its respective to above. degaussing circuit. To establish these individual In order to effectively neutralize the in?uence vector components necessary to neutralize the of this ?eld upon the magnetized elements of a compass, another ?eld is established through the 30 vector DG produced by the coil M, the individual windings 3|, M and Bi of the compensating coils center of the compass which is equal and op S0, 40 and 50 are energized from the source II posite to the ?eld illustrated by the vector DG. in order that the vector sum of the component This is preferably accomplished in my invention ?elds produced by these compensating windings by establishing component ?elds along three axes which are mutually arranged at 90° so that the 35 may at all times equally oppose the vector DG, the currentv for supplying these windings being resultant will be equal and opposite .to the vector preferably obtained from the resistor i4 con DG. nected in series with the M coil. This resistor In Fig. 2, I have illustrated the vector DG as l s is designed to supply a voltage di?erence across resolved into its three components, the vertical component V and two horizontal components 40 its terminals of about six volts when the maxi mum rated current flows in the M coil. The HS and Hp. As illustrated, the axes of the three current magnitude in each compensating wind components are mutually arranged at 90° with ing 3 I, ti and 5! may be separately regulated by the two horizontal components H5 and Hp falling the potentiometers 34, at and 55, respectively, along the line drawn at an angle of 45° forward the starboard and port beam respectively of the 45 'so that no change in magnetic ?eld will occur at the center of the binnacle when the degaussing vessel Ill. The axes of the starboard and port M coil is turned on or the current through it horizontal components thus contains the inter is varied. When the resistors 34, M and 54 have cardinal compass points when the ship head is once been set, their settings need not be altered north or south magnetic. I have resolved the vector DG into components along these lines ar 5.0 with changes in degaussing current. For the purposes of illustration, the degaussing ranged at 45° relative to the beam primarily for coils F and Q are shown energized from a separate convenience since from an inspection of Fig. 3 it motor-generator set l5 through the reversing will be apparent that the corrector coils 3&3 and 40 may be conveniently located with their axes on switches 86 and H and the addustable resistances these .45" lines without impairing the vision of 55 l8 and i9, respectively. Three separate wind ings 32, t2 and 52 are provided on the compen 'the compass card and without interfering with the compensating spheres and/or compensating sating coils 30, t0 and 50 respectively for the magnets. degaussing F coil. The current for these wind ings is obtained from the resistance 2! placed If the magnetic ?eld is set up along each of the ' vector components equal in magnitude but op on in series with the F coil and regulation of the current delivered to' each of the windings is ac posite in direction from the ?eld represented by the vectors V, H; and Hp, the effect of the vector complished by adjusting the resistors 34, 44 and ‘ ‘5d,.respectively, so that no change in the fore DG would be neutralized. In this manner, the and aft, athwartships, or vertical, magnetic force effect of the degaussing ?eld on the compass would be compensated for by simply properly pro 65 occurs across the center of the binnacle with the portioning the magnitude of each of the said degaussing coil F turned on or o?‘ or the current component ?elds. through it varied. When the resistors 34, it and In Fig. 1, there is illustrated in plan view the 541 have once been adjusted, their settings need general outline of the degaussing coils M, F and - notbe altered with changes in degaussing cur‘ Q. The M coil of the vessel i0 is energized from rent. Three windings 33, 43 and 53 are also pro a suitable generator ll through the reversing vided on the compensating coils 30, 4!! and 50 switch l2 and the series resistors l3 and H. respectively for the degaussing Q coil. _, The cur The resistor 13 is adjustable to vary the current rent for these windings is obtained from a resist= magnitude to the M coil. Let it be assumed that. ance 22 placed in series with the Q coil. The the resistor I3 is set to a value whereby the ?eld 76 proper ratio of current magnitude in each of 5 these cells to the current magnitude in the Q coil is established by the variable resistors 35, t5 and 55. Once the current ratios have been ' properly adjusted for this, the last effective de gaussing coil, the operation of all compensat ing coils or windings will be entirely automatic and the magnetic compass will continue to point in the direction of the magnetic north at all times for other degaussing coils (F, G. A or S), the heeling eflects of which are sufficient to war rant provision of compensating windings. In adjusting the current ratio in the hori zontal correcting coils, the dip needle is replaced by the compass and all of the degaussing coils are deenergized. The vessel is then placed on a steady northeast or southwest heading by the and on all headings. magnetic compass. The M coil is now energized I have purposely limited the several views to 10 and the deviation of the compass noted. Since three degaussing coils, namely M, F and Q, and the north and south line of the compass or the also to three separate windings ‘on each of the axis of the compass needle 24 is at an angle compensating coils. However, it should be ob vious from the foregoing that other coils known of 45° to the left of the ship’s center line‘, the axis of the magnetic needle 24 coincides with to the art as A and S coils may also be used, and 15 the component Hp, thus the deviation of the if these coils appreciably affect the compass, a compass upon this intercardinal heading can be compensating winding may be provided therefor. It has been my observation, however, that in caused only by the degaussing ilelds horizontal component He which is 90° from the axis of the most ships the compass is/aifected only by two - component Hp. The compensating component degaussing coils depending upon the location 20 may, therefore, be created by energizing the wind or" the binnacle relative to the coils. The for ward compasses are usually a?ected only by the M and F coils, whereas, the aft compass will be aifected only by the M and Q coils. I ing 4! of the port coil to and adjusting the re sistance 44 until the compass needle returns to the original northeast or southwest heading. Without changing the heading, . the procedure For a better understanding of the speci?c struc outlined above is repeated for adjusting the vwind tures involved in the arrangement of these coils ings 42 and 43 of the coil 40 for the horizontal on the binnacle, reference may be had to Figs. component H5 01’ the degaussing coils F and Q. 3 and 4 of the drawings wherein reference nu Adjustment of the current in the individual meral 20 is used to indicate the compass. For winding of the starboard coil 30 is accomplished the purpose of illustration, a compass bowl 23 is 30 by a procedure similar to that set out above uti illustrated as containing a pivoted compass needle lizing a single degaussing coil at a time with the 24 and is supported in the binnacle 25 by knife ship won a steady northwest or southeast head edge pivots on gimbal rings (not shown). The 1118. binnacle also supports the soft iron hollow spheres If desired, the'compass needle may be de?ected 26 which are mounted on each side of the binnacle relative to the ship rather than swinging the ship - so that their distance from the compass may be to maintain the respective headings. This can varied and a holder 21 for the Fiinders bar. The be accomplished by carefully placing permanent coils 30 and 40 are shown mounted on the star magnets about the binnacle so as to create a de board and port sides, respectively, of the fore ?ecting ?eld perpendicular to the bisector of the and aft center line of the ship with the axis of 40 angle between the original and the desired de each at an angle of 45° relative thereto and on a ?ected position of the compass needle. level with the axis of the-compass needle 24. As Although I have shown and described certain may be seen from Fig. 4, the heeling coil 50 con and specific embodiments of the present inven sists of a number of turns of a multiconductor tion, I am fully aware of the ‘many possible modi cable wrapped about the binnacle. This type of coil is preferable since it is adaptable to binnacles of various sizes and shapesvbut preformed coils may also be used. Access to the terminals of each conductor is had through the Junction box 28 so that the number of turns or‘ number of 50 separate windings maybe varied. ' The heeling coil 50 compensates for the ver tical component of the resultant degaussing ?eld ?cations. Therefore, this invention is not to be restricted except insofar as is necessitated by prior art and the spirit of the subioined claims. The invention described and claimed herein may be manufactured and used by and for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor. I claim: - , in the center of the binnacle- The current‘ 1. In a system for automatically compensating through the heeling coil is adjusted by replacing a magnetic compass for errors produced by the the compass with a conventional dip needle 11degaussing ?eld of a vessel upon which the com lustrated in Fig. 5. . The procedure for adjusting pass is mounted comprising the combination of the current in the heeling coil is as follows: a pair of degaussing coils disposed in a predeter With all of the degaussing coils deenergized and mined spaced relation on said vessel, a pair of with all of the compensating coil control circuits 60 compensating coils each having at least two set at zero, the dip needle BI is brought into separate coaxial windings, a binnacle for support balance by adjusting the weight 6] provided ing the compass, means securing the compensat thereon. The M coil is now energized to the ing coils to said binnacle with the axis of each maximum rated current and the dip or unbal coplanar with the horizontal and vertical axes of ance of the needle is noted. This unbalance 65 the rotatable element of said compass and dis is due to the vertical component V of the M posed on opposite sides of the fore and aft cen coil and may be compensated for by adjusting ter line of said vessel at an angle of 45° relative the resistor 54 to increase. the current in the thereto, so as to contain the intercardinal com winding ll of the heeling coil 50 until the dip pass points when the axis of said vessel coin needle '80 is again brought to a. balanced position. 70 cides with the magnetic meridian, and means when properly compensated, the 'dip needle energizing said degaussing and compensating should remain balanced for any setting of the coils with a direct current _so that the current resistor l3.' ' . 1 magnitude in each degaussing coil and its re Procedure similar to that set forth above is spective winding of each compensating coil may followed for adjusting the heeling components 76 beseparately adiustedtomcintslns?xedrstio. 7 . 2. In a system for automatically compensating 5. In a system for automatically compensating a magnetic compass for errors produced by the a magnetic compass for errors produced by the degaussing ?eld of a vessel upon which the com degaussing ?eld of the vessel upon which the pass is mounted comprising in combination at compass is mounted, comprising the combination least a pair of degaussing coils, said coils being :1 of a pair of degaussing coils disposed in a prede disposed in a predetermined spaced relation on termined spaced relation on said vessel, a source said vessel, a source of direct current electrical of direct current potential, means energizing said potential, means energizing said coils from said coils from said direct current source to neutralize source to produce a resultant magnetic ?eld for the magnetic ?eld of said vessel, at least a pair neutralizing the magnetic ?eld of said vessel, of compensating coils arranged on said vessel in three compensating coils each having at least predetermined space relation closely adjacent two separate and coaxial windings, the axes of' to said compass, means energizing each of said each of said coils being mutually disposed at right coils from the said source so that the current angles, means securing said coils to said vessel magnitude in each compensating coil will main in a predetermined ?xed space relation to said 15 tain a ?xed ratio with the current magnitude compass with the axis of one vertically disposed in a separate one of said degaussing coils. relative to said vessel, and with the axes of the 6. In a system for automatically compensating remaining coils substantially coplanar whereby a magnetic compass for errors produced by the the said axes establish the direction of the hori magnetic ?eld of the degaussing circuit of a ves zontal and vertical components of a space vector sel upon which the compass is mounted compris extending from the center of said compass, means ving the combination of at least a single degaus connecting a separate winding of each of said sing coil disposed in predetermined spaced rela compensating coils in circuit with a separate de tion on said vessel, means energizing said coil to gaussing coil so -that the current magnitude in produce a resultant degaussing ?eld variable in each of said windings may be separately adjusted magnitude and direction with changes in head in suitable proportion to the current magnitude ing and latitude, respectively, of said vessel, to in its respective degaussing coil whereby to pro at all times at least partially neutralize the ship’s duce a magnetic ?eld equal in magnitude but op magnetic ?eld, and means disposed closely adja posite in sense and direction to the component cent said compass for continuously producing a of the resultant degaussing ?eld at the center of 30, resultant compensating ?eld of a magnitude equal said compass, as produced by said separate de to the magnitude of said resultant degaussing gaussing coil having a direction along the axis ?eld at the center of said compass but of an op of said winding. posite sense. 3. In a system for automatically compensating '7. In a system for automatically compensat ' a magnetic compass for errors produced by the ing a magnetic compass for errors produced by degaussing ?eld of a vessel upon which the com the magnetic ?eld of the degaussing circuit of‘ pass is mounted, the combination including at a vessel upon which the compass is mounted, least a pair of degaussing coils disposed in a pre comprising the combination of at least a pair of determined space relation on said vessel, a pair degaussing coils disposed in predetermined spaced of compensating coils each having at least a pair 40 relation on said vessel, means energizing said of separate and coaxial windings, the axes of said coils to produce a resultant degaussing ?eld var coils being substantially coplanar and horizon iable in magnitude and direction toyneutralize on tally disposed relative to said vessel, means se varying heading and in varying latitudes the curing each of said compensating coils to said magnetic ?eld of said ship, means for producing vessel in a ?xed predetermined space relation closely adjacent said compass a compensating closely adjacent to said compass, a source of di ?eld along a vertical axis through the center of rect current electrical potential, means connect said compass, means for producing closely adja ing each degaussing coil to said source, and cent said compass a compensating ?eld having an means connecting a separate winding of each of axis in a horizontal plane containing the axes said compensating coils in circuit with a sepa 50 of the rotatable element of said compass, means rate degaussing coil so that the current magni automatically varying the strength and direction tude in each of said windings may be separately of said compensating ?elds in accordance with adjusted in suitable proportion to the current variations in the strength and direction of said magnitude in their respective degaussing coils to degaussing ?eld whereby the resultant of said automatically compensate for the horizontal com horizontal and vertical component ?elds will be ponent of said degaussing ?eld. equal in magnitude but opposite in sense to the 4. In a system for automatically compensat magnitude and direction of said resultant de ing a magnetic compass for errors produced by gaussing ?eld at the center of said compass. the degaussing ?eld of the vessel upon which the 8. In a system for automatically compensat compass is mounted, comprising in combination 00 ing a magnetic compass for errors produced by at least a pair of degaussing coils disposed in a the degaussing ?eld of a vessel upon which the compass is mounted comprising the combination of a degaussing coil disposed in a predetermined predetermined space relation on said vessel, a compensating coil vertically disposed relative to said vessel and having at least two separate coaxial windings, said compensating coil being closely adjacent to said compass, a source of di~ rect current potential, and means connecting each degaussing coil and a respective winding of said compensating coil to said source so that the current magnitude in each degaussing coil 70 and the current magnitude in its respective wind ing will bear a ?xed ratio whereby no change in the vertical magnetic force at the center of said compass will result from variations in the cur- _ rent magnitude in said degaussing coils. spaced relation to said compass, a source of di rect current electrical potential, means ener gizing said coil from said source to produce a magnetic ?eld to at least partially neutralize the magnetic ?eld of said vessel, a compensating coil, means securing said compensating coil to said vessel in a predetermined spaced relation closely adjacent to said compass, and means con necting said compensating coil in circuit with said degaussing coil so that the current mag 75 nitude in said compensating coil may be ad» 9 2,412,617 10 Justed to maintain a ?xed ratio with the current magnitude in said degausslng coil. 9. In a system for automatically compensating a magnetic compass for errors produced by the 10. In a system for automatically compensat ing a magnetic compass for errors produced by the magnetic ?eld of the degaussing circuit of degaussing ?eld of a vessel upon which the com prising the combination of at least one degauss a vessel upon which the compass is mounted com pass is mounted comprising the combination of ing coil disposed in predetermined spaced rela a degaussing coil disposed in a predetermined tion on said vessel, means energizing said coil to spaced relation on said vessel, three compensat produce a resultant 'degaussing ?eld, variable in ing coils secured in predetermined spaced rela magnitude and direction with changes in head tion closely adjacent to said compass with the 10 ing and latitude, respectively, of said vessel, to axis of each mutually disposed at right angles, at all times at least partially neutralize the ship’s and means connecting each of said compensating magnetic ?eld, and means for producing a mag- coils in circuit with said degaussing coil so that netic ?eld at the compass which has a magnitude the current magnitude in each of said windings variable with said degaussing ?eld to maintain a may be separately adjusted in suitable proportion 15 ?xed ratio therebetween, and a direction oppo to the current magnitude in the degaussing coil site the direction of said degaussing ?eld at the when the said degaussing coil is connected to a center of said compass. direct current source of electrical potential. HOWARD JENKINS.