{"id":208,"date":"2019-01-16T08:17:20","date_gmt":"2019-01-16T08:17:20","guid":{"rendered":"http:\/\/tis-eg.com\/en\/?p=208"},"modified":"2019-01-16T08:17:20","modified_gmt":"2019-01-16T08:17:20","slug":"linear-potentiometer","status":"publish","type":"post","link":"https:\/\/tis-eg.com\/en\/linear-potentiometer\/","title":{"rendered":"linear potentiometer"},"content":{"rendered":"\n\n\n\n\n\n
Potentiometer<\/caption>\n
\"Potentiometer.jpg\"<\/a><\/p>\n
A typical single-turn potentiometer<\/div>\n<\/td>\n<\/tr>\n
Type<\/th>\nPassive<\/a><\/td>\n<\/tr>\n
Electronic symbol<\/a><\/th>\n<\/tr>\n
\"Potentiometer<\/a>\u00a0(IEC Standard)
\n\"Potentiometer<\/a>\u00a0(ANSI Standard)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

A\u00a0potentiometer<\/b>\u00a0is a three-terminal<\/a>\u00a0resistor<\/a>\u00a0with a sliding or rotating contact that forms an adjustable\u00a0voltage divider<\/a>[1]<\/a><\/sup>. If only two terminals are used, one end and the wiper, it acts as a\u00a0variable resistor<\/b><\/i>\u00a0or\u00a0rheostat<\/b><\/i><\/a>.<\/p>\n

The measuring instrument called a\u00a0potentiometer<\/a>\u00a0is essentially a\u00a0voltage divider<\/a>\u00a0used for measuring\u00a0electric potential<\/a>\u00a0(voltage); the component is an implementation of the same principle, hence its name.<\/p>\n

Potentiometers are commonly used to control electrical devices such as volume controls on audio equipment. Potentiometers operated by a mechanism can be used as position\u00a0transducers<\/a>, for example, in a\u00a0joystick<\/a>. Potentiometers are rarely used to directly control significant power (more than a\u00a0watt<\/a>), since the power dissipated in the potentiometer would be comparable to the power in the controlled load.<\/p>\n

Applications.<\/span><\/h2>\n

Potentiometers are rarely used to directly control significant amounts of power (more than a watt or so). Instead they are used to adjust the level of analog signals (for example\u00a0volume<\/a>\u00a0controls on\u00a0audio equipment<\/a>), and as control inputs for electronic circuits. For example, a light\u00a0dimmer<\/a>\u00a0uses a potentiometer to control the switching of a\u00a0TRIAC<\/a>\u00a0and so indirectly to control the brightness of lamps.<\/p>\n

Preset potentiometers are widely used throughout electronics wherever adjustments must be made during manufacturing or servicing.<\/p>\n

User-actuated potentiometers are widely used as user controls, and may control a very wide variety of equipment functions. The widespread use of potentiometers in consumer electronics declined in the 1990s, with\u00a0rotary encoders<\/a>, up\/down\u00a0push-buttons<\/a>, and other digital controls now more common. However they remain in many applications, such as volume controls and as position sensors.<\/p>\n

Theory of operation.<\/span><\/h2>\n
\n
\"\"<\/a><\/p>\n
A potentiometer with a resistive load, showing equivalent fixed resistors for clarity.<\/div>\n<\/div>\n<\/div>\n

The potentiometer can be used as a\u00a0voltage divider<\/a>\u00a0to obtain a manually adjustable output voltage at the slider (wiper) from a fixed input voltage applied across the two ends of the potentiometer. This is their most common use.<\/p>\n

The voltage across\u00a0R<\/i>L<\/sub><\/span>\u00a0can be calculated by:<\/p>\n

\n
{\\displaystyle V_{\\mathrm {L} }={R_{2}R_{\\mathrm {L} } \\over R_{1}R_{\\mathrm {L} }+R_{2}R_{\\mathrm {L} }+R_{1}R_{2}}\\cdot V_{s}.}<\/span>\"V_{{\\mathrm<\/span><\/dd>\n<\/dl>\n

If\u00a0R<\/i>L<\/sub><\/span>\u00a0is large compared to the other resistances (like the input to an\u00a0operational amplifier<\/a>), the output voltage can be approximated by the simpler equation:<\/p>\n

\n
{\\displaystyle V_{\\mathrm {L} }={R_{2} \\over R_{1}+R_{2}}\\cdot V_{s}.}<\/span>\"V_{{\\mathrm<\/span><\/dd>\n<\/dl>\n

(dividing throughout by\u00a0R<\/i>L<\/sub><\/span>\u00a0and cancelling terms with\u00a0R<\/i>L<\/sub><\/span>\u00a0as denominator)<\/p>\n

As an example, assume<\/p>\n

\n
{\\displaystyle V_{\\mathrm {S} }=10\\ \\mathrm {V} }<\/span>\"V_{{\\mathrm<\/span>,\u00a0{\\displaystyle R_{1}=1\\ \\mathrm {k\\Omega } }<\/span>\"R_{1}=1\\<\/span>,\u00a0{\\displaystyle R_{2}=2\\ \\mathrm {k\\Omega } }<\/span>\"R_{2}=2\\<\/span>, and\u00a0{\\displaystyle R_{\\mathrm {L} }=100\\ \\mathrm {k\\Omega } .}<\/span>\"R_{{\\mathrm<\/span><\/dd>\n<\/dl>\n

Since the load resistance is large compared to the other resistances, the output voltage\u00a0V<\/i>L<\/sub><\/span>\u00a0will be approximately:<\/p>\n

\n
{\\displaystyle {2\\ \\mathrm {k\\Omega } \\over 1\\ \\mathrm {k\\Omega } +2\\ \\mathrm {k\\Omega } }\\cdot 10\\ \\mathrm {V} ={2 \\over 3}\\cdot 10\\ \\mathrm {V} \\approx 6.667\\ \\mathrm {V} .}<\/span>\"{2\\<\/span><\/dd>\n<\/dl>\n

Due to the load resistance, however, it will actually be slightly lower:\u00a0\u2248 6.623\u00a0V<\/i><\/span>.<\/p>\n

One of the advantages of the potential divider compared to a variable resistor in series with the source is that, while variable resistors have a maximum resistance where some\u00a0current<\/a>\u00a0will always flow, dividers are able to vary the output voltage from maximum (V<\/i>S<\/sub><\/span>) to\u00a0ground<\/a>\u00a0(zero volts) as the wiper moves from one end of the potentiometer to the other. There is, however, always a small amount of\u00a0contact resistance<\/a>.<\/p>\n

In addition, the load resistance is often not known and therefore simply placing a variable resistor in series with the load could have a negligible effect or an excessive effect, depending on the load.<\/p>\n","protected":false},"excerpt":{"rendered":"

Potentiometer A typical single-turn potentiometer Type Passive Electronic symbol \u00a0(IEC Standard) \u00a0(ANSI Standard) A\u00a0potentiometer\u00a0is a three-terminal\u00a0resistor\u00a0with a sliding or rotating contact that forms an adjustable\u00a0voltage divider[1]. If only two terminals are used, one end and the wiper, it acts as a\u00a0variable resistor\u00a0or\u00a0rheostat. The measuring instrument called a\u00a0potentiometer\u00a0is essentially a\u00a0voltage divider\u00a0used for measuring\u00a0electric potential\u00a0(voltage); the component […]<\/p>\n","protected":false},"author":1,"featured_media":209,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[18],"tags":[],"class_list":["post-208","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-articles"],"_links":{"self":[{"href":"https:\/\/tis-eg.com\/en\/wp-json\/wp\/v2\/posts\/208","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/tis-eg.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/tis-eg.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/tis-eg.com\/en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/tis-eg.com\/en\/wp-json\/wp\/v2\/comments?post=208"}],"version-history":[{"count":1,"href":"https:\/\/tis-eg.com\/en\/wp-json\/wp\/v2\/posts\/208\/revisions"}],"predecessor-version":[{"id":210,"href":"https:\/\/tis-eg.com\/en\/wp-json\/wp\/v2\/posts\/208\/revisions\/210"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/tis-eg.com\/en\/wp-json\/wp\/v2\/media\/209"}],"wp:attachment":[{"href":"https:\/\/tis-eg.com\/en\/wp-json\/wp\/v2\/media?parent=208"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/tis-eg.com\/en\/wp-json\/wp\/v2\/categories?post=208"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/tis-eg.com\/en\/wp-json\/wp\/v2\/tags?post=208"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}