US 3723938 A
A potentiometer for accurately varying the electrical resistance exhibited between two terminals thereof as a specified non-linear mathematical function of the unit-by-unit extent of movement of a movable contact along an elongate resistance element which overlies an array of discrete conductor members whose areal extent and areal disposition under and in bridging contact with the film are such that the specific mathematical function is simulated in variation of the exhibited resistance. In circular-track elements, representative functional relationships include 90 DEG sine, 180 DEG sine, 360 DEG sine, 20db log, single-sided square, and double-sided square.
Claims available in
Description (OCR text may contain errors)
United States Patent [191 Gramm  NON-LINEAR POTENTIOMETER WITH CONDUCTOR ARRAY  Inventor: Eugene R. Gramm, 1448 West 11.
Street, Ontario, Calif. 91762  Assignee: Bowins, Inc.
 Filed: Dec. 22, 1969  Appl. No.: 886,807
 US. Cl. ..338/162, 338/176, 338/308, 338/92  Int. Cl. ..H01c 9/02  Field of Search ..338/89, 90, 92, 95,118, 140, 338/150,160,162,176, 308,142
 Relerences Cited UNITED STATES PATENTS 2,134,870 11/1938 Fruth ..338/142 2,632,831 3/1953 Pritikin... ....338/324X 3,161,850 12/1964 Klug .338/308 X [451 Mar. 27, 1973 3,379,567 4/1968 Wright ..338/89 X Primary Examiner-Robert K. Schaefer Assistant Examiner-Gerald P. Tolin Attorney-William G. Becker  ABSTRACT A potentiometer for accurately varying the electrical resistance exhibited between two terminals thereof as a specified non-linear mathematical function of the unit-by-unit extent of movement of a movable contact along an elongate resistance element which overlies an array of discrete conductor members whose areal extent and areal disposition under and in bridging contact with the film are such that the specific mathematical function is simulated in variation of the exhibited resistance. in circular-track elements, representative functional relationships include 90 sine, 180 sine, 360 sine, 20db log, single-sided square, and doublesided square.
10 Claims, 6 Drawing Figures Patented March 27, 1973 lA/I/EA/TOR EUGENE R. GRAMM NON-LINEAR POTENTIOMETER WITH CONDUCTOR ARRAY BRIEF SUMMARY OF THE INVENTION a. Background of the Invention Heretofore it has been known to provide so-called function potentiometers, an exhibited output potential of which varied approximately in accord with a mathematical function relative to movement of the actuator, to
such as a shaft. Such potentiometers have largely comprised wirewound resistance elements, the resistance wire of which was'wound either with varying spacing of convolutions of the wound wire, or with varying lengths of wire per turn as in the case of shaped-card elements. Great care in winding the elements was required, and irrespective of such care, close matching of successively wound elements was seldom attained, and the elements were bulky and of restricted resolution as are all wirewound resistance elements. It also has been suggested that a non-linear potential variation might be obtained without involving all of the noted known undesirable physical and electrical characteristics of wirewound non-linear potentiometers, by laying down in a base a circular series of radially extending conductive strips with their faces flush with the surface of the base, dimensioning the strips variably as to width, length and spacing, laying down a continuous film of carbon or other resistance material over a portion of each strip and between the strips, leaving the inner end of each strip exposed for contacting, and arranging a movable contact to be moved successively from one to the next exposed strip end. The latter suggested proposal, exemplified by the structure disclosed in US. Pat. No. 2,632,831, did not attain practical status since the resolution of the device was even poorer than that provided by wirewound function-elements, the value of resistance exhibited changing in step-like changes of value of inconstant magnitude and spacing relative to contact movement.
b. The Present Invention By the present invention, gross improvements in resolution are attained over the prior art function-simulating potentiometers, by utilizing a uniform film of resistance material, such as a cermet, for the resistance element, and driving a movable contact along an elongate brushing track orsurface of the element. The resistivity of the film is as uniform as it is practicable to make it, and the resistance exhibited between the movable contact and either terminal of the element is made to vary non-linearly relative to unit-by-unit movement of the contact along the element, by appropriate dispersal of a multiplicity of discrete precisely dimensioned and precisely arrayed conductor members in the form of conductive films in areal contact with one face of the resistance element and laterally distant from the track or path on which the contact is arranged to travel. Conveniently the array of discrete conductor members or conductive films is produced on the insulative face of a support or substrate, concurrently with production thereon of film-like conductors which serve as taps and/or terminals for the resistance element. Such conductive appurtenances or components are, with the exception of those portions which are to serve as exposed terminals, covered wholly or in part by a film-like layer of resistive material, such as a cermet or conductive plastic" material, which film extends beyond the lateral boundary of the elongate area or zone in which the array of discrete conductive components are dispersed, to provide a brushing or contact zone alongside the array of conductor members. The movable contact is arranged to brush the resistive film along a contact path in the contact zone, none of which overlies or is in contact with any of the conductive members; that is, the contact is so arranged that it brushes the resistance element along a path which is confined to that area of the resistive film that extends beyond the noted lateral boundary of the elongate area in which the conductive discrete films are deployed or arrayed. Thus the movable contact does not brush any of the conductive components nor does it brush any portion of the resistive film immediately underlaid or overlaid by any conductive component. Thus the exhibited potential variation or resistance variation is not undulatory or stepped in character, but smoothly increases and decreases as the contact moves along the contact path. As will be made clear, the dimensions, I
areal extents, and areal spacings and dispositions of the conductor members underlying one elongate zone of the resistance element, depend upon the particular mathematical function or relationship which the potential output of the potentiometer is desired to simulate or follow. Exemplary spatial and areal arrangements of the two types of active components, i.e., resistive and conductive, and a presently preferred physical arrangement in a complete exemplary potentiometer, are illustrated in the accompanying drawings comprised in this specification or description.
The preceding brief summary of the invention and its background make it evident that it is a principal object of theinvention to provide improvements in variable resistors or potentiometers of the type in which the output potential is made to vary non-linearly and according to a determined mathematical function of, or with respect to, linear variation of position of a movable contact.
Another object of the invention is to provide general improvements in function-generating potentiometers.
Another object of the invention is to provide an arrangement of potentiometer components by means of which a high degree of uniformity or alikeness of electrical characteristics is attained among all of similarly produced potentiometers. I
Another object of the invention is to provide improyements in manufacturing of that class of variable resistors termed function potentiometers.
Another object is to provide improvements in precision in non-linear precision potentiometers.
Other objects and advantages of the invention are hereinafter set out or made evident in the appended claims and the detailed description of the illustrated form of the invention.
DESCRIPTION OF THE DRAWINGS FIG. 1 is a pictorial view of an exemplary single-turn rotary potentiometer embodying the preferred form of the invention, with portions of a structural element and of resistive material removed to reveal details;
FIG. 2 is a pictorial view of a cylindrical resistance element device adapted for axial rotation and incorpo'rating principles of the invention, using resistive material shown as being transparent;
. FIG. 3 is a pictorial representation of an elongate rectilinear resistance element device according to the invention, using resistive material illustrated'as being transparent for convenience in illustration; and
FIG. 4, 5 and 6 are plan views of three illustrative resistance element devices according to the invention, illustrating arrays of discrete conductor members used to provide, respectively, 40db log, 20db log, and 360 sine functional outputs in a potentiometer such as that depicted generally in FIG. 1, the resistive materials of the devices being shown as though they were transparent for convenience in illustration, and portions thereof removed to better portray details.
In the drawings, no specific scale of distance measure is applied.
DETAILED DESCRIPTION In accord with the principles of the present invention, a preferred form of resistance element device is produced by disposing within a determined boundary on an insulative base, such as a ceramic substrate, a carefully dimensioned and configured elongate array of discrete spaced-apart conductor members, such as thin metallic films each having a particular specific geometrical or areal shape or configuration and each particularly disposed in the array relative to next-adjacent members of the array, then disposing on the substrate and over and laterally beyond the array of conductor members a film of resistive material, the latter extending laterally beyond and outside of the boundary of the array of conductor members whereby to provide a brushing path or track for accommodation of the wiper or contact of the potentiometer distant from the array of conductor members. The array of conductors is elongate in the direction of travel or motion of the movable contact of the potentiometer, whether in an arcuate, cylindrical, or rectilinear disposition. The resistance element is provided with terminations at its electrical ends, and may have intermediate termina tions or taps, all of which preferably are of conductive film formed of material like or similar to that of the members of the noted array. The film terminations may connect directly, or by means of wires, to respective 22e may in instances be transparent, or translucent, it
may be opaque and of the nature of a cermet film or'of the nature of a resistive plastic film. The metallic members 22c are in this example adherent to the substrate,
being preferably formed by silk-screen application of a metal-containing ink which is fired to fuse the metal to the substrate. The resistive material may be similarly applied, and fired if of the nature of a cermet, or cured if a conductive plastic. The conductive members may be of diverse geometrical or areal configurations, but are all disposed within a specified elongate boundary. For example, the arcuate array of members 22c, most of which are obscured in FIG. 1 by the remainder of the overlying opaque resistive film 22e, is restricted to an arcuate zone or region, herein denoted X-Y, and extending from an inner circular boundary denoted X, and an outer circular boundary arbitrarily indicated by the dash or broken line Y in FIG. 1. Thereby there is provided an arcuate zone or region, herein denoted Y'-Z, adjacent to but laterally distant from zone XY in which the conductive members are contained, in which zone Y-Z the resistive material is not underlain by the conductive members and within which is the path along which the movable contact or contacts of a contact device 20d may brush the resistive element.
As previously indicated, the number, areal extents,
, and areal dispositions of the conductor members 22c rigid insulated pin terminals affixed to the base or substrate or to other convenient structure. Other pertinent and detailed features of the invention are described in the following explanation containing references to the drawings.
In FIG. 1, the exemplary potentiometer 10 comprises a housing composed of a cup 12, a cap or cover 14, and a clamp band 16, a part of which has been broken away and the flanges of which engage in beveled annular grooves in the cap andcup to retain the housing in assembled form when the ends of, the band are drawn together by the screw 16'. Antifriction bearing means, such as that at 18 in the cover l4,are coaxially ar ranged in the housing to rotatably support a contact actuator 20 herein shown as a shaft 20s and wiper arm 20a. Affixed in the bottom of cup 12 as by. means of adhesive'is the resistance element device 22 which in the form shown comprises a substrate 22s in the form of a vary widely, dependingupon the particular functional variation it is desired-that the electrical output of the potentiometer follow, upon the physical size 'of the potentiometer, the relative dimensions of the noted zones and their relative positions, and like design factors. The members 22c are discrete, that is, they are separated on the substrate by intervening areas of insulation and by intervening portions of the resistive material of the resistive element 22c. The relative arrangement of the array of members 22c and the brushing or contact zone within which the contact path is situated may be other than as shown in FIG. 1; for example, in an arcuate or annular substrate arrangement, the zone in which'the array of conductive members is disposed may be radially outward from the contact zone, in which case the contact device 20d would be appropriately attached to wiper arm 20a inwardly of the position shown. A return conductor may be alternatively provided by producing a circular conductive ring 22r adjacent the inner edge of the annular substrate-as shown in FIG. 1, or by use of a metal ferrule or ring attached to the substrate or to the bottom wall of cup 12 In either case, connection of the contact device to the return conductor is effected by means of a conductive 'brush 20r conductively attached to the metal wiper arm 20a of the actuator means. The returnconductor Mr is insulated fromthe resistive element 22c and the conductor members 22c by an'intervening bare annular portion 22s of the substrate, as indicated in FIG. 1.
In operation, the shaft 20s, rotating in the noted bearings, rotates the arm 20a and carries the contact device 20d alongthe elongate arcuate contact path in the brushing zone Y-Z adjacent to but external to the boundaries of thearray of conductor members. The
values of electrical resistance exhibited between the movable contact device and any selected termination or tap on the resistive element vary in dependence upon the displacement of the contact or brushing point of device d from the respective termination, and, unlike the situation in an ordinary potentiometer, the values will vary non-linearly with respect to units of displacement of the contact point from a zero position at which the exhibited value is zero. Further, the values will vary smoothly and closely in accord with a desired mathematical (functional) relationship, due to the effects of the discrete conductive members 220 substantially short-circuiting or bridging carefully selected small discrete areal extents of the resistive layer or film comprised in resistive element 22e. The variation of the noted exhibited resistance will not be step-wise, nor undulatory or wavy when recorded in graphical form, as is the case when a contact moves from turn to turn of a wire element or from contact to contact of a series of stationary switch contacts; but will, rather, be smooth and follow very closely the intended mathematical functional variation and when graphically recorded will result in a record coinciding with the. graphical plot of the function. It is evident that due to the noted bridging effects of the discrete conductor members, the variation of exhibited resistance, relative to extent of travel of the contact along the contact path, will not be linear and will vary from a linear relationship to an extent depending upon the areal size and spacing or distribution of the conductor members underlying the resistive element, the relative areas of the latter element that are within, and external to, the zone within which the conductive members are arrayed, and the respective resistivities of the conductor members and the element. Thus to produce a potentiometer whose electrical output will follow a specific functional relationship to the linear motion or advance of the actuator and contact, a graphical representation of the desired functional variation may be plotted, together with a comparable graphical plot representing linear variation of exhibited resistance relative to actuator or contact displacement. Then the deviations of the first plot or graph from the second graph may be noted for a large number of ac tuator displacements. Using experimental data obtained by production of a resistance element device similar to 22, but including a diversity of areal patterns and dispositions of conductive members, and measurement of values of exhibited resistance variations from linear values, an approximate or proposed array of conductor members is produced, and conformity or nonconformity with the desired functional variation is determined at diverse points along the course or extent of the element. Any resulting non-conformity from the desired variation is or may be corrected by small change of areal shape or extent of appropriate conductor members, whereby to obtain an exact arrangement or array of the latter necessary to attain the desired degree of conformity of variation of exhibited resistance to the specified functional variation. Thereafter, in successively produced potentiometers of the same construction or type, the exact arrangement of conductor members is repeated, using the areal array previously-determined as a pattern, to provide a variation of electrical potential output, or exhibited resistance, conforming to thespecified functional relationship.
It is evident from the preceding description that by using areal arrays of conductive members disposed upon, or under, respective resistive element films as described, substantially any specific non-linear function in two variables can be matched to any desired degree of exactness. Smoothness of the variation of exhibited resistance can be decreased by decreasing the width or transverse dimension of the resistive material zone such as zone Y-Z in FIG. 1, relative to the transverse dimension of the zone in which the conductive member array is disposed, and/or by changing the width of the resistive zone between the contact zone and zone X-Y, and vice versa. Also it is evident that the resistive element and the array of conductor members may take other than arcuate form. For example, the resistive element, and the conductor members array, may be disposed upon a cylindrical surface as indicated in FIG. 2, or upon a flat rectangular elongate surface as indicated in FIG. 3. In FIG. 2, a cylindrical insulative substrate 30, with gudgeons 32 and 32' permitting rotational supporting in a housing, has secured thereto a functionally related elongate array of discrete conduc tor members 34 and an overlying adherent arcuate resistive element 36. A contact zone 36c is provided, remote from the zone 36e within which the boundaries of the conductor members array are contained, whereby the brushing contact 38 is always distant from the nearest conductor member of the array. A set of conductive bands 40 and 42, adherent upon isolated portions of the substrate 30, serve as return conductors, each connected to a respective end termination of element 36 and brushed or contacted by a respective one of a set of brushes 44 and 46. In that construction, the contact and brushes may be stationary and the substrate actuated by exerting or applying torque to the rotatable structure, as, for example, to the gudgeon 32.
In FIG. 3 is illustrated an elongate flat rectangular wafer-like substrate 50 of insulation bearing an array of thin flat discrete conductor members such as 52, which members are overlaid by an elongate resistive element 54 that extends laterally beyond the boundaries of the elongate zone occupied by the conductor members and longitudinally into contact with transverse end termination conductor films 56 and 56'. Thus there is provided an elongate contact zone 58 distant from the conductor-member array and upon which a contact device 60 brushes incident to relative longitudinal motion between the substrate and the contact device. Terminals are provided for the element 54 as required, as by wire leads soldered to terminations 56, 56' and to contact device 60 as indicated; but other conventional terminal means may be utilized. As is evident, the lengths, widths and spacings of the conductor members of the array may be varied, and the geometrical shapes thereof as well, to bring the variation of resistance exhibited between contact 60 and termination 56, for example, incident to relative longitudinal translation between contact and resistive element, into conformity with the corresponding functional variation of any specified function of two variables. Thereafter, the conductor member array, etc., are duplicated or copied to produce any desired number of functionally and operationally alike potentiometers.
In FIG. 4, there is illustrated a resistance element device suitable for direct incorporation into a potentiometer structure such as that depicted in FIG. 1, in
substitution for the device 22 therein, and adapted to provide a resistive or electrical representation of the function commonly termed 40db log, more precisely defined by the equation e/E 10" wherein e is the potential difference between wiper contact and an end termination, E is the potential difference between end terminations, and x represents displacement of the wiper contact from an end termination. In the drawing, the film of the elongate annular resistive element 70 has been partly removed and the remainder shown as though it were transparent. In general, the resistive film may be opaque, semi-opaque, translucent, or transparent, depending upon the materials and processes employed; but herein the expedient of illustrating the film of the resistive element as'being transparent is util-' ized solely to improve clarity of illustration. The resistive element 70 in this example overlies a major portion of the elongate arcuate zone within which is contained the invisible and intangible boundaries of an elongate arcuate array of discrete conductor members such as those indicated by number 72. The conductor members are formed on an annular flat washer-like ceramic wafer or substrate 74, for example by being silk-screened thereon using conductive or metallic ink and then fired, or by any other appropriate process. In this particular instance, the conductor members are of large areal extent and of arcuate sector form at one end of the array; decreasing in areal extent but of relatively uniform separation as the other end of the array is approached, and diminishing in size to short line-segment form at the latter extremity of the array, as shown. Radially inward extremities of the individual conductor members are in this instance not overlaid by the resistive film of element 70, illustrating another feature of the invention as will presently be explained. Further, it should be noted that the conductor members array ends before the adjacent termination :2 is reached, whereby there is left a short arcuate section of the resistive element that is not underlain by conductor members. That is necessitated by the nature of the 40db log function that the electrical output of the potentiometer is required to follow. When the substrate 74 is substituted for device 22 shown in the potentiometer 10 illustrated in FIG. 1, the terminations Hand :1 are wire-connected to respective ones of pins T, and a metal ring or ferrule similar to Mr of FIG. is applied to the inner periphery of substrate 74 for brushing by brush 20r. It will be understood that whether the entire area of each of conductive members 72 is overlaid by resistive film or element 70, or only partially covered, is a matter of design; and that the extent to which the total width of the resistive film is bridged by conductor members is similarly a matter of design. Initially, to determine the areal'shape, areal extent, and spacing of the conductor members, the latter may optionally be applied over the resistive film, to the extent required to produce the change of exhibited resistance requisite to follow the specified functional relationship between the variable movement or translation of the actuator or contact, and of the exhibited electrical quantity (resistance or potential). The areal configuration is varied, as is the areal extent, progressively, and by steps to provide discrete conductor members, from one end of the array to the other, with correlated reading-out of the electrical values as modified by production or application of the discrete members as necessary to obtain correspondence between the functional relationship to be followed and the electrical value exhibited. Thereafter the areal configurations of the resistive element and of the array of conductive members are repeated or copied for each of a series of substrates for like potentiometers.
Further illustrating application of the principle of the invention to resistance element devices which may be used in the housing members 12-14 of FIG. 1, there is shown an arrangement in FIG. 5 very similar to that depicted in FIG. 4 but adapted to provide an output following the 20db log function represented mathematically by the similar equation e/E 10" wherein the characters of the equation are the same as those previously identified in the functional relationship explained in connection with FIG. 4. The differences between the resistance element devices depicted in FIGS. 4 and 5 are principally differences in areal shapes and extents of the conductor members and in the areal distributions or dispositions thereof in the respective arrays. The substrate 74 carries an elongate array of conductor members such as 72', a resistive element 70 and terminations t1 and t2.
Further illustrating how more complex mathematical functional relationships are made to be followed by the potentiometer output, by differently forming and areally arranging the conductor members relative to the elongate resistive element, there is depicted in FIG. 6 a resistance element device 80 suitable for substitution for that shown at 22 in FIG. 1, with the utilization of two more pins T of the terminal pin array there shown. In FIG. 6, the thin annular alumina ceramic substrate has applied thereto an elongate array of discrete conductor members 82 of areal shapes and extents as indicated, the array being comprised of two op-' positely disposed sub-arrays, each the mirror-image of the other, but the upper (as shown) sub-array having its middle members connected to respective ones of separate terminations T1 and T2 which serve as the two end terminals of the overlying elongate annular resistive element 84, while the middle conductor members of the lower (as shown) sub-array are merged with and connected to a common termination T3 which serves as a mid-point tap termination for the resistive element 84. The resistive film 84 is tapped by quarterpoint conductive taps at T4 and T5 as shown, and conductor films suchas 85, 86 and 86' are optionally formed on the substrate concurrently with the conductor members, to facilitate short-wire connections to closely spaced terminal pins of the array of pins T affixed to the potentiometer as indicated in FIG. 1. Such insulated-wire connectors are indicated at W in FIG. 6.
An electrical return ring or conductor 88 is provided atthe inner margin of the annular ceramic substrate, as shown, for contact with brush 201'; and the conductor 88 is connected by a wire W to one of the terminal pins T. The areal arrangement of the conductor elements, their extents, and their positioning relative to the overlying resistive film of the resistive element 84 is such as to provide a sin 360" functional variation of the exhibited resistance, or of the electrical output of the movable potentiometer contact [such as wiper contact 20d (FIG. 1)]. Mathematically, the function is represented by the equation: e/E sin 0, wherein e output potential, E is the total applied potential, and is the angular displacement of the contact 20d along the resistive element from a termination T1 or T2.
In each of the foregoing constructions, the preciseness with which the electrical output conforms to the respective desired functional relationship between contact displacement and electrical output (exhibited resistance or exhibited potential) may be brought to any desired degree-of tolerance by appropriately changing or altering the point-to-point resistance of the film of resistive material comprised in the resistive element. For example, as indicated in FIG. 6, by selective careful removal of resistive material from successive portions of the area adjacent the inner periphery of the annular film, as indicated at R1, R2, R3 and R4 in the drawing, adjustment of the electrical output value can be brought into conformity with the theoretical value dictated by the equation, to any desired degree of precision. Removal of the material can be removed by sandblasting, or by laser beam. In the case of potentiometers manufactured to ordinary tolerances, such trimming of the resistive film is not necessary.
The preceding detailed description of the invention as embodied in potentiometers having resistance element devices of a variety of configurations, and the detailed description of the means and mode of disposing an elongate array of discrete conductor members of various areal configurations, extents and spacing relative to a transversely distant elongate brushing or contact zone of a thin elongate resistive element, portions of which element are bridged by respective ones of the conductor members whereby to make the electrical output of the potentiometer vary in accord with a specifiedmathematical function, make it evident that a substantially infinite number of non-linear functional relationships between two variables may be accommodated by respective constructions according to the invention. Accordingly, it is not desired that the scope of the invention be limited to the specific details of the illustrated structures, but that the scope be restricted only by limitations expressed in the appended claims.
1. An electrical non-linear function-generating potentiometer comprising:
first means, including housing means providing a chamber;
second means, including an actuator device having a driving portion in said chamber and a portion accessible outside said chamber for imparting actuating motion thereto;
third means, including an insulative substrate in said chamber, and an array of discrete conductor members arrayed .on said substrate and adherent thereto;
fourth means, comprising a resistive film overlying said conductor members and presenting an elongate exposed surface distant from said array for brushing contact by movable contact means, and terminal means for said film;
fifth means, including movable contact means in said chamber and a terminal for said contact means, said contact means moved by said actuator means along an elongate path included in said elongate exposed surface whereby to vary the value of electrical resistance exhibited between said contact means and either of said terminal means,
whereby variation of said-value during movement of said contact means accurately follows a known non-linear mathematical function of such movement determined by the areal extents and areal distributions of said discrete conductor members overlaid by said resistive film.
2. A potentiometer according to claim 1, in which the said actuator device is rotary and in which the areal extents and dispositions of said discrete conductor members provide variation of the said exhibited value of resistance proportional to the sine of the angular displacement of said actuator device.
3. A potentiometer according to claim 1, in which the said actuator device rotates and in which the areal extents and spatial dispositions of said conductor members provide a variation of said exhibited value of resistance exponentially related to linear rotational displacement of said actuator device.
4. For a non-linear potentiometer theelectrical output of which varies in conformity with a non-linear mathematical relationship between the displacement of the potentiometer actuator and such electrical output,
first means, comprising a resistance element device comprising an insulative substrate and first and second superposed thin elongate components both adherent to said substrate, said first component comprising an elongate thin film-like resistive element, I
said second component comprising an elongate array of thin film-like discrete conductor members each having a face and each having at least a portion of a face thereof in contact with and bridging a complementary portion of the said resistive element,
said elongate array of discrete conductor members leaving unbridged an elongate contact zone of said resistive element laterally adjacent to said array;
second means, including termination means for said resistive device; and
third means, including actuator means and a contact operated thereby along a contact path in said contact zone laterally distant from said array.
5. A non-linear potentiometer resistance element device comprising:
a thin insulative ceramic substrate;
an elongate thin film of resistive material forming a resistive element, said element adherent to said substrate and supported thereon and providing first and second elongate zones along the length thereof said zones including a brushing contact zone and a bridging zone extending alongside said brushing contact zone;
an elongate array of areally separated conductor members in face to face contact with respective portions of said resistive element entirely within said bridging zone and generally laterally distant from said brushing contact zone, said conductor members and said resistance element being superimposed upon and supported by said ceramic substrate; and
' mined mathematical function relating exhibited resistance and such departure as determined by the bridging effects of said conductor members upon the said resistive element.
6. A resistance element device as defined in claim 5, in which said conductor members are conductive films fired upon said substrate and in which said resistive element is a thin elongate film of resistive material which in said bridging zone overlies and is partially bridged by at least portions of said conductor members and which film is adherent to both said discrete conductor members and to said substrate.
7. A resistance element device as defined in claim 6, in which said film of resistive material is a cermet.
8. A resistance element device as defined in claim 6, in which said film of resistive material is a resistive plastic composition.
9. A resistance device comprising an insulating substrate with a thin film resistive element, said resistive element including a first zone extending lengthwise of ment and a second zone extending lengthwise of the element and across the portion of the element width not occupied by said first zone, an elongate array of thin discrete conductor members permanently disposed in contact with said resistive element solely in said first zone, and a movable contact engaging said resistive element and operated along a path in said second zone laterally distant from said array.
k i i i it .UNITED STATES PATENT ()FFKH'I CERTIFICATE OF CORRECTION Patent No. 3,723, 938 Dated MarCh 27, 1973' 3 Inventor(s) Eli gene R. Gr lmm It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:
Assignee: "Bowins, Inc. should read -B0urns, Inc.
signe'd 'ahd sealed this 12th day of November 1974.
McCOY M. GIBSON. JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents m'm) S'lA'lEb PATEN'I owm-z CERTIFICATE OF CORRECTION Patent No. 3,723,938 Daterl March 27, 1973 Inventor(s) Eugene R. Gramm It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:
Assignee: "Bowins, Inc." should read -Bourns, Inc.-.
Signed 'aind sealed this 12th day of November 1974.
McCOY M. GIBSONJR. C. MARSHALL DANN Attesting Officer Commissioner of Patents