US3832670A

US3832670A - Multiple precision potentiometer

Info

Publication number: US3832670A
Application number: US00306910A
Authority: US
Inventors: G Oman
Original assignee: Johnson Service Co
Current assignee: Johnson Service Co; Johnson Controls International Inc
Priority date: 1972-11-16
Filing date: 1972-11-16
Publication date: 1974-08-27
Anticipated expiration: 1991-08-27
Also published as: CA996210A

Abstract

A wide range and high resolution potentiometer is provided by using a plurality of variable resistor pairs and a base potentiometer. The pairs are connected together in two complementary series chains on either side of the base potentiometer. A slide means is connected to each pair in a ganged relation to selectively vary their resistance in equal but opposite direction so that the total input resistance of the potentiometer always remains constant. Each pair added multiplies the basic resolution of the potentiometer.

Description

United States Patent [19] Oman [111 3,832,670 1 Aug. 27, 1974 MULTIPLE PRECISION POTENTIOMETER [75] Inventor: Gary F. Oman, Greensdale, Wis.

[73] Assignee: Johnson Service Company,

Milwaukee, Wis.

22 Filed:- Nov. 16, 1972 21 Appl. No.: 306,910

[52] US. Cl. 338/124, 338/180 [51] Int. Cl H016 1/16 [58] Field of Search 338/196, 122, 123, 124,

[56] References Cited UNITED STATES PATENTS 2,836,690 5/1958 Barr 338/124 2,881,295 4/1959 Brown..... 2,972,123 2/1961 Blom 338/122 X Primary Examiner-E. A. Goldberg Assistant ExaminerDavid A. Tone Attorney, Agent, or Firm-Johnson, Dienner, Emrich, Verbeck and Wagner [57] ABSTRACT A wide range and high resolution potentiometer is provided by using a plurality of variable resistor pairs and a base potentiometer. The pairs are connected together in two complementary series chains on either side of the base potentiometer. A slide means is connected to each pair in a ganged relation to selectively vary their resistance in equal but opposite direction so that the total input resistance of the potentiometer always remains constant. Each pair added multiplies the basic resolution of the potentiometer.

3 Claims, 3 Drawing Figures r 1 MULTIPLE PRECISION POTENTIOMETER BACKGROUND OF THE INVENTION Present ,potentiometers of the partial turn and multiturn type used for in-circuit adjustments are limited in their resolution to the resolution provided by the basic wiper mechanics and the resistance element. Although a multi-turn unit offers better resolution than a single turn unit, there is no way, at present, to multiply the resolution of a potentiometer while still maintaining the same wiper mechanics resolution and resistance element resolution.

Accordingly, one object of this invention is to provide a potentiometer with wide range and high resolution.

A further object of this invention is to provide a potentiometer such that its resolution is not limited by the wiper mechanics and resistance element.

A still further object of this invention is to provide a means for adding variable resistance elements in order to multiply the potentiometer resolution.

SUMMARY OF THE INVENTION This invention functions as a standard potentiometer but is capable of increased resolution without the usual need of sacrificing rangel The potentiometer embodying the principles of my invention comprises a base potentiometer with an adjustable output tap and one or more pairs of variable resistors having shiftable taps connected in two complementary chains on either side of the base potentiometer. A ganged means is provided for moving the shiftable taps of each pair in unison such that the effective resistance of each resistor varies in equal and opposite amounts to its mate in order that the input resistance of the potentiometer remains constant. The basic resolution of the potentiometer is thus multiplied by the addition of each pair of resistors.

DESCRIPTION OF DRAWINGS For a better uderstanding of this invention, reference may be made to the accompanying drawings in which:

FIG. 1 is an electrical schematic diagram for a potentiometer circuit embodying the principles of myinvention',

FIG. 2 is a plan view of one arrangement of the FIG. 1 schematic diagram; and

FIG. 3 is a front perspective view of a case for housing the arrangement of FIG. 2.

DESCRIPTION OF PREFERRED EMBODIMENT There is depicted in FIG. 1, an electrical schematic diagram showing the circuit arrangement of a wide range, high resolution potentiometer generally designated by the reference numeral 8 and embodying the principles of my invention. Potentiometer 8 comprises a base potentiometer R and three variable resistor pairs: R and R R and R and R and R The two shiftable taps (10, l2; l4, l6; and 18, 20), of each variable resistor pair (R A R R R and R -R are mechanically ganged together by an associated shiftable means (22, 24 and 26).

Potentiometer 8 has three terminals X, Y and Z, and there are two series circuits, one provided between'ter minals X-Y and the other between terminals Y-Z. One terminal of Resistor R is connected to terminal X, and the position of its shiftable tap 10 provides effective resistance R Likewise, one terminal of resistor R is connected to tenninal Z, and the position of shiftable tap 12 determines the value of effective resistance R Variable resistors R and R are connected in tandem between base resistor R and variable resistor R As a result the effective resistance of R R and R and R are connected in series between terminals X and Y. Similarly, variable resistors R and R are connected in tandem between base resistor R and variable resistor u- The resistors of any given pair (R R R R and R R have identical values and characteristics with each other so that the repositioning of its associated shiftable means (22, 24 or 26) causes the effective resistance of one of the resistors of the pair to increase by an amount equal to the decrease in its paired resistor. For example, displacing shiftable means 22 upwardly, as viewed in FIG. 1 increases the effective resistance R of variable resistor R by an amount equal to the decrease of effective resistance R, of variable resistor R The net effect of this arrangement is that the total input resistance R of the potentiometer 8 does not change and thereby prevents any loading changes onprevious stages as the wiper positions change.

The above described embodiment provides a potentiometer having a wide range with high resolution. By virtue of connecting the ganged variable resistors in a cascade arrangement, it is possible to increase the potentiometer resolution by a factor equal to the number of variable resistor pairs. For example, if the basic resolution of the potentiometer wiper mechanism and resistance element is one part in 10 and the potentiometer resistance equals 100,000 ohms, the resolution would then be 100,000 10 or 10,000 ohms. By using a four stage potentiometer as depicted in FIG. 1 and selecting each-resistor to have a one-tenth resolution, the combined resolution of the potentiometer would be (0.1) or l/10,000. If the variable resistors in FIG. 1 each had a one-tenth resolution and R was set to be K ohms, the combined resolution would be l/l0,000 or 10 ohms. The resistors would be set to have the following values:

R, R 90,000 ohms R R 9,000 ohms R R,- 900 ohms R 100 ohms.

One significant advantage of this invention is that it offers extremely simple construction and yet provides a very accurate potentiometer. Referring to FIG. 2, there is shown one construction of the electrical schematic diagram of FIG. 1, wherein the variable resistors R R R R R R and R are of the conventional inexpensive linear-slide type. Each of the variable resistors are of the same basic construction well known in the art. Briefly, referring specifically to variable resistors R and R of FIG. 2, each comprises a rectangular shaped base of insulation material having a film of resistive material 32. A conductive strip 30 extends alongside each resistor. An insulative slide 34 carries a pair of spaced

contactors

36, 38 along the two resistive paths in yielding engagement with the resistive material 32 and the associated conductive strips 30 of each pair. A lead screw 40 extends crosswise through a threaded opening at the center of slide 34 to define shiftable means 22. The terminals X and Z are provided at the opposite ends of the resistive material strips for resistors R and R in order that movement of slide 34 in either direction will cause changes in their effective resistance to vary in opposite directions.

The FIG. 2 assembly could be housed in enclosed casing as shown in FIG. 3, with openings 50 provided in its front face for adjusting the slides 34, and the three terminals X, Y and Z projecting out through its bottom wall.

This invention is not restricted to a linear motion metal film type resistor as illustrated in FIG. 2. Further it is to be understood the number of pairs of variable resistors could be any quantity being dependent only on the desired resolution. The number of times the res-.

olution can be increased is, therefore, theoretically unlimited.

I claim:

I. A potentiometer comprising: a pair of linear resistors disposed in parallel, side-'by-side relation to each other; a pair of contactors each engaged with only one resistor for determining an effective resistance of the resistor; an insulative slide carrying the contactors; a pair of input terminals each connected to an opposite end of one of the resistors for forming complementary resistive paths from each terminal, along the resistor connected to the terminal and to the contactor engaged with the resistor; and a screw in threaded engagement with the slide for shifting the slide to vary the effective resistance along each path in equal and opposite amounts.

2. A potentiometer having an output terminal and two input terminals comprising: pairs of parallel, sideby-side, variable resistors connected in separate branches, each branch being connected between the output terminal and a different one of the input terminals through an effective resistance of one resistor of each pair of resistors; a contactor engaged with each resistor for determining the effective resistance of each resistor; an insulative slide carrying the contactors for each resistor pair; and a lead screw extending between the resistors and in threaded engagement with the slide to shift the slide and contactors for varying the effective resistance of each resistor of a pair in unison and in equal and opposite amounts thereby maintaining the input resistance of the potentiometer constant.

3. A potentiometer comprising: a base potentiometer having an adjustable output tap; at least one pair of resistors disposed in parallel, side-by-side relation and each resistor of a pair having a shiftable output tap connected to an opposite end of the base potentiometer for forming complementary series branches; a slide carrying the taps for each resistor pair; a lead screw extending between the resistors and in threaded engagement with each slide for moving the slide to shift the taps; and an input terminal connected to each branch completing a resistive path along each branch variable with slide movement in equal and opposite amounts for maintaining the input resistance of the potentiometer constant and multiplying the resolution of the base potentiometer by the number of resistor pairs.

Claims

1. A potentiometer comprising: a pair of linear resistors disposed in parallel, side-by-side relation to each other; a pair of contactors each engaged with only one resistor for determining an effective resistance of the resistor; an insulative slide carrying the contactors; a pair of input terminals each connected to an opposite end of one of the resistors for forming complementary resistive paths from each terminal, along the resistor connected to the terminal and to the contactor engaged with the resistor; and a screw in threaded engagement with the slide for shifting the slide to vary the effective resistance along each path in equal and opposite amounts.

2. A potentiometer having an output terminal and two input terminals comprising: pairs of parallel, side-by-side, variable resistors connected in separate branches, each branch being connected between the output terminal and a different one of the input terminals through an effective resistance of one resistor of each pair of resistors; a contactor engaged with each resistor for determining the effective resistance of each resistor; an insulative slide carrying the contactors for each resistor pair; and a lead screw extending between the resistors and in threaded engagement with the slide to shift the slide and contactors for varying the effective resistance of each resistor of a pair in unison and in equal and opposite amounts thereby maintaining the input resistance of the potentiometer constant.