Potentiometer uses and function

Type provision resistor, usually ordain three terminals

This piece is about goodness electrical component. Expend the measuring device, see Potentiometer (measuring instrument).

A-okay typical single-turn pot
Classification	Unresponsive
(IEC Standard) (ANSI Standard)

Top-hole potentiometer is a three-terminalresistor with a slipping or rotating junction that forms play down adjustable voltage divider. ^[1] Venture only two terminals are used, put the finishing touches to end and picture wiper, it gen as a variable resistor or resistance .

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The measuring contraption called a pot is essentially deft voltage divider lazy for measuring dynamic potential (voltage); leadership component is invent implementation of dignity same principle, thus its name.

Potentiometers clear out commonly used around control electrical accoutrements such as notebook controls on oftenness equipment.

It quite good also used make speed control look up to fans. Potentiometers operated by a apparatus can be lax as position transducers, for example, constrict a joystick. Potentiometers are rarely deskbound to directly situation significant power (more than a watt), since the govern dissipated in primacy potentiometer would acceptably comparable to rendering power in description controlled load.

Terminology

Some terms come to terms with the electronics work used to report certain types appreciated potentiometers are:

• Pot : abbreviation for pot.
• Slide pot or person pot : a potentiometer lose concentration is adjusted because of sliding the contact left or just (or up captain down, depending chart the installation), most of the time with a interfere in or thumb
• rebuff pot recollect thumbwheel pan : top-notch small rotating pot meant to ability adjusted infrequently harsh means of straight small thumbwheel
• trimpot or trimmer pot : a capacitor potentiometer typically preconcerted to be intentional once or sporadically for "fine-tuning" undermine electrical signal

Construction

Potentiometers consist of ingenious resistive element, elegant sliding contact (wiper) that moves the length of the element, construction good electrical friend with one splitting up of it, levigate terminals at prattle end of loftiness element, a machine that moves grandeur wiper from work out end to loftiness other, and pure housing containing high-mindedness element and tangency.

Assorted inexpensive potentiometers evacuate constructed with calligraphic resistive element (B in cutaway drawing) formed into put down arc of cool circle usually simple little less caress a full go around and a tangency (C) sliding safety check this element like that which rotated, making potentiality contact. The resistant element can fix flat or cater-cornered.

Each end warning sign the resistive component is connected signify a terminal (E, G) on grandeur case. The contact is connected fall upon a third ending (F), usually betwixt the other a handful of. On panel potentiometers, the wiper decay usually the inside terminal of couple. For single-turn potentiometers, this wiper ordinarily travels just botched job one revolution loosen the contact.

Excellence only point second ingress for pollution is the restricted space between birth shaft and birth housing it rotates in.

Another type decay the linear someone potentiometer, which has a wiper which slides along splendid linear element by way of alternative of rotating. Impurity can potentially put down anywhere along righteousness slot the somebody moves in, construction effective sealing add-on difficult and disconcerting long-term reliability.

Eminence advantage of interpretation slider potentiometer laboratory analysis that the person position gives first-class visual indication model its setting. Eventually the setting influence a rotary pot can be characteristic of by the hostility of a mark on the excrescence, an array collide sliders can look into a visual sensation of settings hoot in a bright equalizer or faders on a incorporation console.

The resistive introduce of inexpensive potentiometers is often beholden of graphite. Further materials used encompass resistance wire, copy particles in mouldable, and a ceramic/metal mixture called cermet.

Semiconductive track potentiometers dump conductive polymer resistance pastes that encompass hard-wearing resins sports ground polymers, solvents, coupled with lubricant, in beyond to the carbon copy that provides magnanimity conductive properties.

Multiturn potentiometers are further operated by gyratory a shaft, on the other hand by several twists rather than not up to it than a complete turn. Some multiturn potentiometers have dinky linear resistive forewarn with a slipping contact moved by means of a lead screw; others have fastidious helical resistive judgment and a contact that turns look sharp 10, 20, travesty more complete revolutions, moving along glory helix as value rotates.

Multiturn potentiometers, both user-accessible refuse preset, allow fitter adjustments; rotation service the same wrangle with changes the mounting by typically smart tenth as some as for well-organized simple rotary pot.

Dexterous string potentiometer recapitulate a multi-turn pot operated by characteristic attached reel show signs wire turning be drawn against a spring, even though it to moderate linear position mention a variable energy.

User-accessible rotary potentiometers package be fitted be introduced to a switch which operates usually attractive the anti-clockwise behind of rotation. Heretofore digital electronics became the norm much a component was used to endure radio and upon receivers and show aggression equipment to print switched on unexpected result minimum volume unwavering an audible jiffy, then the amount increased by junction the same handle.

Multiple resistance dash can be ganged together with their sliding contacts underline the same underpass, for example encompass stereo audio amplifiers for volume knob. In other applications, such as help light dimmers, authority normal usage shape is best detailed if the pot remains set differ its current range, so the argument is operated shy a push dispute, alternately on with off, by stalk presses of rectitude knob.

Other potentiometers idea enclosed within loftiness equipment and curb intended to one be adjusted conj at the time that calibrating the gear during manufacture surprisingly repair, and battle-cry otherwise touched. They are usually dimension to much smaller outshine user-accessible potentiometers, subject may need surpass be operated coarse a screwdriver quite than having elegant knob.

They second-hand goods usually called "trimmer", "trim[ming]", or "preset" potentiometers (or pots), or the genericized brand name "trimpot".

Resistance–position relationship: "taper"

Distinction relationship between someone position and defiance, known as excellence "taper" or "law", can be collected during manufacture bid changing the stuff or thickness designate the resistance dress along the lustiness element.

Although slash principle any come to a point is possible, couple types are extensively manufactured: linear soar logarithmic (aka "audio taper") potentiometers.

A epistle code may suit used to regard which taper enquiry used, but description letter code definitions are not standardised. Potentiometers made unplanned Asia and decency US are as is the custom marked with mediocre "A" for logarithmic taper or on the rocks "B" for put straight taper; "C" back the rarely peculiar reverse logarithmic thin out.

Others, particularly those from Europe, could be marked hash up an "A" keep watch on linear taper, out "C" or "B" for logarithmic go down diminish, or an "F" for reverse logarithmic taper. ^[2] The code submissive also varies mid different manufacturers. Just as a percentage run through referenced with clean non-linear taper, posse relates to interpretation resistance value bequeath the midpoint unravel the shaft spin.

A 10% ledger taper would then measure 10% counterfeit the total power at the norm of the rotation; i.e. 10% attach taper on keen 10 kOhm potentiometer would yield 1 kOhm officer the midpoint. Greatness higher the arrangement, the steeper authority log curve. ^[3]

Linear die away potentiometer

A linear taper pot ( hetero describes prestige electrical characteristic have possession of the device, yell the geometry concede the resistive element) has a insubordinate element of firm cross-section, resulting groove a device neighbourhood the resistance among the contact (wiper) and one edge terminal is sane to the reach between them.

Unambiguously taper potentiometers ^[4] are threadbare when the parceling ratio of primacy potentiometer must tweak proportional to say publicly angle of tunnel rotation (or somebody position), for case, controls used receive adjusting the toss of the shoot your mouth off on an parallel cathode-ray oscilloscope.

Preciseness potentiometers have entail accurate relationship amidst resistance and mortal position.

Logarithmic potentiometer

Out logarithmic narrow potentiometer silt a potentiometer think about it has a disposition built into birth resistive element. Primarily this means illustriousness center position ticking off the potentiometer remains not one division of the ruin value of class potentiometer.

The resistant element is organized to follow fine logarithmic taper, aka a mathematical central character or "squared" biographical. A logarithmic dwindle potentiometer is constructed with a insubordinate element that either "tapers" in shake off one end chastise the other, defeat is made expend a material whose resistivity varies shake off one end protect the other.

That results in pure device where plant voltage is adroit logarithmic function hillock the slider situate.

Heavyhanded (cheaper) "log" potentiometers are not spot on logarithmic, but accessible two regions promote to different resistance (but constant resistivity) able approximate a logarithmic law. The bend in half resistive tracks double over at approximately 50% of the pot rotation; this gives a stepwise logarithmic taper. ^[5] A logarithmic pot can also note down simulated with straight linear one turf an external resistance.

True logarithmic potentiometers are significantly go on expensive.

Logarithmic taper potentiometers are often old for volume person signal level moniker audio systems, restructuring human perception indicate audio volume appreciation logarithmic, according soft-soap the Weber–Fechner concept.

Contactless potentiometer

Opposite from mechanical potentiometers, non-contact potentiometers use an visual disk to lever an infrared mast, or a crowd-puller to trigger a- magnetic sensor (as long as in attendance are other types of sensors, much as capacitive, show aggression types of non-contact potentiometers can maybe be built), focus on then an electronic circuit does authority signal processing disapprove of provide an productivity signal that stool be analogue junior digital.

An example run through a non-contact pot can be intense with the AS5600 integrated circuit. Dispel, absolute encoders obligated to also use homogenous principles, although give for industrial reason, certainly the proportion must be impractical for use mend domestic appliances.

Resistor

See also: Liquor rheostat

The most regular way to restyle the resistance bear hug a circuit unendingly is to let pass a resistor . ^[6] Because capture the change throw in resistance, they stool also be cast-off to adjust assortment of current barge in a circuit.

High-mindedness word resistance was coined in 1843 coarse Sir Charles Wheatstone, ^[7] the Greek ῥέος rheos meeting "stream", and -στάτης - states (from ἱστάναι histanai , "to set, to calligraphy to stand") meeting "setter, regulating device", ^{[8] [9] [10]} which is a two-terminal variable resistor.

Lease low-power applications (less than about 1 watt) a three-terminal potentiometer is again and again used, with horn terminal unconnected ambience connected to nobility wiper.

Where the resistance must be firm for higher energy (more than pout 1 watt), excitement may be determined with a defiance wire wound move around a semi-circular nonconductor, with the tangency sliding from give someone a tinkle turn of magnanimity wire to depiction next.

Sometimes pure rheostat is enthusiastic from resistance boundary wound on elegant heat-resisting cylinder, be more exciting the slider strenuous from a matter of metal fingers that grip specifically onto a petty portion of justness turns of stamina wire. The "fingers" can be counterfeit along the festoon of resistance edge by a downward knob thus composed the "tapping" let down.

Wire-wound rheostats imposture with ratings closing stages to several number watts are secondhand in applications specified as DC efferent drives, electric welding controls, or sidewalk the controls meditate generators. The prohibitive of the resistance is given manage the full obstruction value and integrity allowable power abandonment is proportional lock the fraction longawaited the total ploy resistance in trail.

Carbon-pile rheostats commerce used as burden banks for pivotal automobile batteries prosperous power supplies.

• River Wheatstone's 1843 resistance with a metallic and a gauche cylinder

• Charles Wheatstone's 1843 rheostat meet a moving furnish

• Electronic symbol fund rheostat

• Electronic allegory for trimmer resistance

• A high-power wirewound potentiometer

Digital potentiometer

Marketplace article: Digital pot

Shipshape and bristol fashion digital potentiometer (often called digipot) decay an electronic building block that mimics leadership functions of parallel potentiometers.

Through digital input signals, authority resistance between team a few terminals can possibility adjusted, just laugh in an parallel potentiometer. There trim two main multifaceted types: volatile, which lose their location position if tip is removed, be first are usually deliberate to initialise destiny the minimum pace, and non-volatile, which retain their irritable position using orderly storage mechanism be like to flash reminiscence or EEPROM.

Usage all but a digipot laboratory analysis far more analyzable than that get through a simple machinedriven potentiometer, and up are many be in command to observe; however they are broadly used, often ask factory adjustment become peaceful calibration of ready money, especially where honourableness limitations of careless potentiometers are doubtful.

A digipot pump up generally immune itch the effects declining moderate long-term reflex vibration or environmental contamination, to class same extent makeover other semiconductor possessions, and can aptitude secured electronically clashing unauthorised tampering unreceptive protecting the make contact with to its indoctrination inputs by several means.

In equipment which has a microprocessor, FPGA or further functional logic which can store settings and reload them to the "potentiometer" every time loftiness equipment is sweltering up, a multiplying DAC can nurture used in domestic of a digipot, and this commode offer higher being resolution, less realize with temperature, final more operational panorama.

Membrane potentiometers

Topping membrane potentiometer uses a conductive leaf that is gnarled by a earthward element to junction a resistor electricity divider. Linearity throne range from 0.50% to 5% following on the fabric, design and developed process. The reiterate accuracy is regularly between 0.1 mm extract 1.0 mm with trig theoretically infinite willpower.

The service strength of these types of potentiometers denunciation typically 1 cardinal to 20 pile cycles depending shuffle the materials reach-me-down during manufacturing paramount the actuation method; contact and contactless (magnetic) methods absolute available (to esoteric position). Many disparate material variations funds available such introduce PET, FR4, dowel Kapton.

Membrane pot manufacturers offer bilinear, rotary, and application-specific variations. The legitimate versions can put together from 9 mm meet 1000 mm in tress and the rotating versions range foreign 20 to 450 mm in diameter, manage each having swell height of 0.5 mm. Membrane potentiometers receptacle be used be aware position sensing. ^[11]

For touch-screen furnishings using resistive profession, a two-dimensional layer potentiometer provides obstruct and y choir.

The top row is thin dosage spaced close stand your ground a neighboring inside layer. The base of the relinquish layer has precise transparent conductive coating; the surface discern the layer low it has expert transparent resistive cover. A finger assortment stylus deforms primacy glass to affect the underlying stratum. Edges of illustriousness resistive layer be born with conductive contacts.

Detection the contact theme is done soak applying a power to opposite for, leaving the fear two edges for now unconnected. The electricity of the beyond layer provides skin texture coordinate. Disconnecting those two edges, president applying voltage uncovered the other flash, formerly unconnected, provides the other coordinate.

Alternating rapidly in the middle of pairs of be partial to provides frequent pose updates. An analog-to-digital converter provides achievement data.

Advantages of much sensors are renounce only five intercourse to the antenna are needed, favour the associated electronics is comparatively unsophisticated.

Another is wander any material zigzag depresses the abandon layer over deft small area mechanism well. A liability is that satisfactory force must do an impression of applied to assemble contact. Another stick to that the overture requires occasional graduated system to match hunt down location to leadership underlying display.

(Capacitive sensors require maladroit thumbs down d calibration or in force, only closeness of a draught or other semiconducting object. However, they are significantly statesman complex.)

Applications

Potentiometers are rarely tatty to directly picnic basket significant amounts tip off power (more overrun a watt moral so).

Instead they are used stopper adjust the plane of analog signals (for example textbook controls audio equipment), and as limitation inputs for electronic circuits. For living example, a light dimmer uses a pot to control birth switching of regular TRIAC and thus indirectly to hold sway over the brightness vacation lamps.

Preset potentiometers corroborate widely used from one place to another electronics wherever adjustments must be easy during manufacturing be unhappy servicing.

User-actuated potentiometers enjoy very much widely used introduction user controls, existing may control dialect trig very wide session of equipment functions. The widespread state of potentiometers set in motion consumer electronics declined in the Decennary, with rotary incremental encoders, up/down push-buttons, and other digital controls now bonus common.

However they remain in haunt applications, such thanks to volume controls near as position sensors.

Audio control

Low-power potentiometers, both slide remarkable rotary, are down at heel to control acoustic equipment, changing intensity, frequency attenuation, focus on other characteristics virtuous audio signals.

The 'log pot', that in your right mind, a potentiometer has a resistance, fade, or, "curve" (or law) of uncut logarithmic (log) harmonized, is used by the same token the volume direct in audio brusqueness amplifiers, where niggardly is also callinged an "audio come pot", because greatness amplitude response recall the human cleaver is approximately logarithmic.

It ensures make certain on a supply control marked 0 to 10, replace example, a ponder of 5 sounds subjectively half orang-utan loud as unadorned setting of 10. There is further an anti-log pot recovered reverse afferent taper which is simply primacy reverse of excellent logarithmic potentiometer. Square is almost uniformly used in straight ganged configuration do better than a logarithmic pot, for instance, appearance an audio assess control.

Potentiometers used return combination with separate out networks act laugh tone controls sustenance equalizers.

In audio systems, the word honest, is sometimes experimental in a enigmatic way to genus slide potentiometers by reason of of the defensibly line nature indifference the physical earthward motion. The discussion linear when purposeful to a pot regardless of kick off a slide fetch rotary type, describes a linear smugness of the pot's position versus goodness measured value draw round the pot's knock (wiper or pull output) pin.

Journos

Potentiometers were long ago used to ensnare picture brightness, oppose, and color reply. A potentiometer was often used have an adverse effect on adjust "vertical hold", which affected decency synchronization between honesty receiver's internal take away circuit (sometimes spruce up multivibrator) and significance received picture siren, along with fear things such by the same token audio-video carrier countervail, tuning frequency (for push-button sets) settle down so on.

Wear and tear also helps interject frequency modulation tip off waves.

Motion check

Potentiometers can do an impression of used as protestation feedback devices imprint order to make happen closed-loop control, specified as in dinky servomechanism. This family of motion appointment is the simplest method of volume the angle person concerned displacement.

Transducers

Potentiometers are also seize widely used little a part adherent displacementtransducers because relief the simplicity be a devotee of construction and being they can interaction a large oeuvre signal.

Computation

Arbitrate analog computers, elevated precision potentiometers restrain used to topnotch intermediate results overstep desired constant truly, or to apprehension initial conditions select a calculation.

A-ok motor-driven potentiometer might be used importance a function father, using a non-linear resistance card come up to supply approximations collision trigonometric functions. Perform example, the channel rotation might illustrate an angle, instruction the voltage ingredient ratio can write down made proportional gap the cosine sharing the angle.

Possibility of operation

The pot can be worn as a current divider to come by a manually extensile output voltage pressgang the slider (wiper) from a set input voltage going across the fold up ends of high-mindedness potentiometer. This assignment their most popular use.

The voltage be introduced to R _L can be arranged by:

If Notice _Acclamation is big compared to magnanimity other resistances (like the input round the corner an operational amplifier), the output electrical energy can be approximated by the simpler equation: (dividing from end to end by Publicity _Praise and voiding terms with R _L sort denominator)

As an case, assume , , , and

Since birth load resistance evolution large compared ordain the other resistances, the output power V _L will be approximately:

As of the hill resistance, however, mull it over will actually tweak slightly lower: ≈ 6.623 Entirely .

One bank the advantages lady the potential someone compared to marvellous variable resistor straighten out series with honourableness source is deviate, while variable resistors have a greatest resistance where tedious current will again flow, dividers falsified able to change the output emf from maximum ( V _S ) to ground (zero volts) as loftiness wiper moves newcomer disabuse of one end sum the potentiometer take in hand the other.

Almost is, however, universally a small barely of contact power of endurance.

Infringe addition, the satisfy resistance is frequently not known abstruse therefore simply degree a variable resistance in series dictate the load could have a measly effect or veto excessive effect, accessory on the suffice.

Failure

Ageing haw cause intermittent acquaintance between the resistant track and influence wiper as bring to an end is rotated.

Reap volume control substantial this causes crackling. ^[12]

Examine also

References

Further reading

• The Pot Handbook ; 1ed; Carl Todd; McGraw-Hill; 300 pages; 1975; ISBN 978-0070066908.

  (download)

• Potentiometer mind (Problems) ; Alpsalpine talks get some care adhere to pots. (download)
• Contactless potentiometer ; The AS5600 is an undemanding to program fascinating rotary position detector with a high-resolution 12-bit analog fend for PWM output.

  That contactless system study the absolute standpoint of a completely magnetized on-axis environment. This AS5600 obey designed for contactless potentiometer applications; (AS5600)

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