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sensors:rotary_potentiometer [2018/06/06 13:20]
admin [Devices]
sensors:rotary_potentiometer [2018/11/01 18:55]
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-====== 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. 
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-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. 
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-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. 
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-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. 
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-====  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. 
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-=====  Devices ​ ===== 
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-{{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= 
-}} 
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-=====  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. 
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-=====  Media  ===== 
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-{{rotary_potentiometer.png?​200|A Rotary Potentiometer}} 
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-=====  External links & references ​ ===== 
-  * [[http://​vipre.uws.edu.au/​tiem/?​tag=rotary-potentiometer|Instruments using rotary potentiometers @ TIEM]] 
-  * [[wp>​Potentiometer]] 
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-{{tag>​Sensor Rotary_position Rotation Potentiometer Resistance}}