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 sensors:rotary_potentiometer [2018/06/06 13:20]admin [Devices] sensors:rotary_potentiometer [2018/11/01 18:55] Line 1: Line 1: - ====== Rotary Potentiometer ====== - =====  Summary ​ ===== - ====  Introduction ​ ==== - The word **potentiometer** comes from //​potential//,​ which refers to voltage potential, or difference. ​ A potentiometer (sometimes called a **pot**) is a device for measuring voltage difference. ​ In fact, a potentiometer is simply a resistor with a variable resistance value. ​ Typically it is composed of a resistive material through which a current is passed. ​ Unlike a static resistor, however, the point at which the current exits the resistive material is variable. ​ Most often this is done by using a brush, which makes electrical contact with the resistive material, and which can be moved using a handle. ​ By moving the brush, the voltage potential being measured can be modified. - - The voltage of a potentiometer may not necessarily vary linearly. ​ In other words, if you turn the knob at a constant speed, a linear potentiometer will respond with a voltage exactly proportional to your distance around the circular range. ​ However, if the potentiometer has a **logarithmic** response curve, it will vary as a logarithmic proportion. - - The reason for the existence of logarithmic potentiometers is because there are many variables, especially in the world of audio and psycho-acoustics,​ which are logarithmic by nature. ​ For example, we hear "​loudness"​ of audible sound in terms of decibels (dB).  [[wp>​Decibels]] are a logarithmic value. ​ Therefore, to hear an apparent linear change in loudness, we must adjust volume levels logarithmically. ​ Every notch on the volume knob of your stereo system is actually an increase in exponential power. ​ Another example is pitch, where every time you increase pitch by an octave, you are actually doubling the frequency. ​ For controlling these types of variables, a logarithmic potentiometer should be used. - - An alternative shape for the rotary potentiometer is the [[linear potentiometer (slider)]], where the word "​linear",​ in this case, refers to its physical shape of a straight line. - - ====  Variations ​ ==== - For audio applications,​ it can be useful to use the same value to modify two or more signals. ​ For this purpose, it is possible to get stereo pots, which apply the same resistance to two seperate circuits. - - =====  Devices ​ ===== - - {{template>​device - |company=Panasonic - |model=ECG EVL-HFAA06A53 - |sources=[[http://​ca.digikey.com/​scripts/​DkSearch/​dksus.dll?​Detail?​Ref=329740&​Row=442197&​Site=CA\|Digikey.ca]] CDN\$ 2.57 - |description=13mm. 5 KΩ - |datasheet=[[http://​www.panasonic.com/​industrial/​components/​pdf/​aok0000ce3.pdf\|pdf]] - |resources= - |notes= - |variants= - }} - - =====  Alternatives ​ ===== - Another method for reading rotary position is by using a [[rotary encoder]]. ​ The main difference between a rotary potentiometer and an encoder is that the potentiometer can measure //​absolute//​ position, while the encoder can measure only //​relative//​ position. ​ The advantage of a rotary encoder is that it can turn in the same direction indefinitely,​ while a  potentiometer will typically only turn once around. ​ Also, an encoder requires digital logic (hardware or software) to read position, while the potentiometer can be directly used in an analog circuit. - - =====  Media  ===== - - {{rotary_potentiometer.png?​200|A Rotary Potentiometer}} - - =====  External links & references ​ ===== - * [[http://​vipre.uws.edu.au/​tiem/?​tag=rotary-potentiometer|Instruments using rotary potentiometers @ TIEM]] - * [[wp>​Potentiometer]] - - {{tag>​Sensor Rotary_position Rotation Potentiometer Resistance}}