Originally a term potentiometer was wont to decribe an apparatus utilized to measure a potential (or voltage) inside the circuit by tapping polish off the part of the known voltage from either the resistant slide wire & comparing it by owning the unknown voltage by means of a voltmeter or galvanometer.

A present popular usage of the term potentiometer (or even 'pot' for short) describes an electronic component which has a user adjustable resistance. Unremarkably, this occurs as 3-terminal resistance by owning the sliding call for in the center. Whenever altogether ternary terminals come utilized, it acts as a variable voltage divider. Potentiometers come likewise widely utilized as a a portion of displacement transducers because of the simplicity of construction and because it could give the big output.

Original potentiometer
A original potentiometer occurs as nature and severity of bridge circuit for measuring voltages. A word itself derives from either a sentence "voltage potential," & "potential" was utilized to refer to "strength." A original potentiometers come divided into quadruplet independent classes: a constant trend lines potentiometer, a constant todays potentiometer, a microvolt potentiometer & a thermocouple junction potentiometer.

Constant current potentiometer
This is utilized for with measurements of voltages beneath Ace.Five volts. Therein circuit, the unknown voltage is attached through a part of trend lines wire the terminates of which are then attached to a standard electrochemical cell that provides the constant current through the wire, The unknown voltage, serial sustaining the galvanometer, is so attached through the variable-length subdivision of the trend lines wire applying the sliding email(s). the sliding call for even is moved until there are no todays flows into or away from a standard cell, every bit indicated by a galvanometer in series with a unknown voltage. A voltage through a selected segment of wire is so capable the unknown voltage. Everthing that remains is to calculate a unknown voltage from either a todays & a fraction of the length of the trend lines wire that was attached to the unkown electromotive force. A galvanometer doesn't want to exist when calibrated, as its just work is to see zero. Whenever a galvanometer reads zero, there are no todays is drawn from either a unknown voltage then a reading is independent of the source's internal trend lines.

Constant resistance potentiometer
the constant trend lines potentiometer occurs as variation of the basic idethe where a variable todays is fed across a fixed resistance. Which are actually utilized primarily for measuring in the mv & microvolt range.

Microvolt potentiometer
This occurs as form of a constant trend lines potentiometer described above however intentional to minimise the results of email trend lines & thermal voltage. This devices is satisfactorily utilized down to readings of 10nV or even and then.

Thermocouple potentiometer
A second development of a standard types was the 'thermocouple junction potentimenter' especially modified for performing temperatue measuring sustaining thermocouple junction. [http://physics.kenyon.edu/EarlyApparatus/Thermodynamics/Thermocouple_Potentiometer/Thermocouple_Potentiometer.html]

Modern potentiometer
This occurs as trio terminal resistor where the position of the sliding connection is user adjustable.(Although a term varistor. . implies the similar work, the varistor is non a equivalent device as a potentiometer.Understand a varistor article for details. Tuning capacitors are every now and again incorrectly known as potentiometers, even due to their similar appearance. Whenever the device has simply deuce terminals brought retired (or even if only the slider & of these prevent of a 3-terminal device come utilized) these are known as a variable resistor, or even variable resistor. This is utilized to control current. 'Pots' are non wont to control high-high-voltage equipment, like electrical stoves, because as a voltage divider or even variable resistor, power is inherently lost. A pot may actually be hotter than a heating element of the stove. Most common applications for pots include volume controls in audio equipment and (fossil oil) weak dimmers. Around consumer electronics every now and again a in-on/off switch for a device is combined using a volume control such that good past a setting least volume, the device turn off.

Types of potentiometers

Low-power types
The potentiometer is constructed applying the flat graphite annulus as the insubordinate element, by owning a sliding call for (wiper) sliding around this annulus. A wiper is attached to an axle &, via a second rotating email, is brought out when a third terminal. In panel pots, a wiper is commonly a centre terminal. For only turn pots, this wiper often travels good under a single revolution around a email. 'Multiturn' potentiometers besides survive, in which a resistance element can be helical and the wiper might move Decade, Twenty, or even additional complete revolutions. Additionally to black lead, more materials can be utilized for the insubordinate element. THese can be trend lines wire or even carbon particles in polymer or even the ceramic/metal mixture. the single popular form of circular potentiometer is known as a string pot. These are the multi-turn potentiometer by using an bonded reel of trend lines wire turning against the spring. It's super ready to h& for with measurements of movement and so acts as a position transducer. Within the linear slider pot, the sliding control is provided instead of the dial control. A word linear likewise describes a geometry of the resistant element which occurs as rectangular strip, (non an annulus as in the circular potentiometer). Because of their construction, this nature and severity of pot has the greater likely for receiving dirty. Potentiometers may be found sustaining either linear or logarithmic laws.

Linear potentiometers
The linear law pot ("type B") has a insubordinate element of constant cross-division, resultant around a device in which the trprevent lines between the wiper & 1 end terminal is proportional to the distance between the two. Linear describes a electrical 'law' of a device, non the geometry of the resistant element. Logarithmic potentiometers
The log pot ("type A") (every now and again known as the log taper pot) has a insubordinate element that either 'tapers' inside the logarithmic manner from either either either of these prevent to the more, or even is mass produced from the poop whose electrical resistance varies logarithmically from 1 prevent to the more. This outcomes inside a device in which a few feet away between the wiper & 1 prevent terminal is proportional to the log of the trend lines between the two. A 'log pot' is utilized when a volume control inside audio amplifiers, where these are likewise known as an "audio taper pot", because a amplitude response of the human ear is also logarithmic. It ensures that, in the volume control marked 0 to Ten, for instance, the setting of Fin sounds half when loudly as a setting of 10. There exists likewise an anti-antilogarithm pot or even reverse audio taper ("type C") which is only the reverse of a log pot. These are most universally utilized withwithin the ganged configuration sustaining the log pot, e.g., in an audio balance control.

High-power types
The variable resistor is basically the potentiometer, however is ordinarily great deal big, designed to address tremendously higher voltage & todays. Usually which are actually constructed as the insubordinate wire wrapped around a toroidal core with a wiper give way a upper surface of the toroid, sliding from either 1 turn of the wire to the next. Every now and again the variable resistor is processed from either either trend lines wire wound in the heat resisting cylinder using the slider manufactured from the total of metallic fingers that grip lightly onto a little part of the turns of trend lines wire. A 'fingers' may be moved along a coil of trend lines wire by a sliding knob so changing the 'tapping' point. It is normally utilized when variable resistors like than variable possible dividers.Variable resistor detail *[http://humboldt.edu/~scimus/HSTC.2735/CatDesc/RheostatBKH.gif]

Digital control

Understand digitally-controlled potentiometer.

Theory of operation

A 'modern' potentiometer may be utilized as a likely divider (or even voltage divider) to obtain the manually adjustable output voltage at a slider (wiper) from either a fixed input voltage applied through them stops of the pot. This is the usual utilize of pots.

A voltage through $R\_\backslash mathrm$ is determined per formula:

V_\mathrm\cdot V_s

A parallel lines indicate components in parallel. Expanded fully, a equation becomes:

V_\mathrm\cdot V_s

Although these are non universally a out break, in case $R\_\backslash mathrm$ is big in comparison a more resistances (such as a input to an operational amplifier), the output voltage may be estimated per simpler equation:

V_\mathrm\cdot V_s

For instance, accept $V\_\backslash mathrm$ is roughly:

\approx Sextet.667\ \mathrm

Ascribable the bucket trend lines, notwithstanding, it might actually exist as slightly moo: ≈ Sextuplet.623 V.

One of a benefits of a possible divider in comparison the variable resistor is that, when variable resistors have a maximal trend lines in which a select few current will always flow, dividers come breaa to diverge the output voltage from either maximal ($V\_S$) to ground (zero volts) when a wiper moves from either 1 prevent of the pot to the more. There exists, nonetheless, universally the little total of call for trend lines.