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While I was taking notes I get confused by the component named "potentiometer", I don't know in which category I should place it.

If I'm correct the definition of a sensor is broadly "a component that converts other form of energy to electrical form" and an actuator is the reverse.

Is a potentiometer a sensor or an actuator or both or neither?

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    \$\begingroup\$ By what logic would you consider a potentiometer to be an actuator? \$\endgroup\$ – Hearth May 24 at 4:39
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    \$\begingroup\$ My logic is that it apply a "transformation" in the current acting like a resistance. So I don't know if that transformation should count as an actuator kind of thing. \$\endgroup\$ – cortantief May 24 at 4:46
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    \$\begingroup\$ An actuator, as I would define it, is something that takes an electrical input and produces a mechanical output. So things like motors, solenoids, pumps, that sort of thing. A potentiometer isn't even close to what I would consider an actuator. \$\endgroup\$ – Hearth May 24 at 4:57
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    \$\begingroup\$ Ah, let me see. (1) Sensors senses physical values, usually analog, such as temperature, pressure, etc, which are inputs from nature, and usually outputs a voltage signal to be converted by ADC to a digital value. (2) On the other hand, actuators such as relay, motor, accept control signals which can be digital or analog signals, and outputs are physical movements, such as switch open/closed, motor shaft turns CW or CCW etc. / to continue, ... \$\endgroup\$ – tlfong01 May 24 at 5:05
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    \$\begingroup\$ From a logic application perspective (i.e. IoT), a sensor is mainly a source of data (i.e. an input), whereas an actuator is primarily a target to command (i.e. an output). That is, a potentiometer is typically bound to an input, hence falls in the "sensor" class, to me. Of course, you may theoretically use a potentiometer as a dissipating target, but this sounds weird in the majority of cases. \$\endgroup\$ – Mario Vernari May 24 at 5:32
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A potentiometer gives output (resistance) in response to a physical input (position). So that puts it pretty squarely in the ‘sensor’ category.

And they all go to 11...

enter image description here

At the risk of dissecting the live frog, from here: https://en.m.wikipedia.org/wiki/Up_to_eleven

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    \$\begingroup\$ Sounds a bit as if resistance isn't physical :) \$\endgroup\$ – Gregory Kornblum May 24 at 14:02
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    \$\begingroup\$ +1 for S.T. reference. \$\endgroup\$ – Klik May 24 at 17:40
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    \$\begingroup\$ @hacktastical Let us continue this discussion in chat. \$\endgroup\$ – SamGibson May 24 at 19:13
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An electrical sensor is a device that converts a specific physical parameter to an electrical signal. A potentiometer as a level sensor, for example, would fit into this category.

An electrical actuator is an electromechanical device that converts an electrical signal to a mechanical movement. A solenoid actuator would be one such example.

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A sensor converts a non-electrical measurement to a (commonly electrical) signal representing it. An actuator converts a (commonly electrical) signal to a physical effect.

For a potentiometer to be a "pure" electrical sensor, you'd put a constant voltage across its track and pick of a voltage representing the position from the wiper. While this is increasingly done in a manner as simple as that (and has the advantage to be comparatively robust against noise and crackling when changing the position), at least classical designs make potentiometers have a more complex role in a circuit, like being part of a voltage divider working on an AC signal.

There are complex in-between things: for example, a relais (or optocoupler) does not function as an actuator unless you split it into its constituent components or view it through the lens of creating noise or magnetic fields. A quartz crystal is neither sensor nor actuator even though it works through mechanical vibration (and fixating its case may be necessary to ensure reliable operation parameters).

A spark plug is clearly an actuator though its principal effects can be considered electrical.

A resistor is not usually considered an actuator, but a resistor thermically coupled to a crystal oscillator and used as a heating element for stabilising its operating frequency is functioning as an actuator.

So it's all a bit handwavy. But a potentiometer clearly is not an actuator on its own, though a thing like a "motor fader" in a mixing desk controller does contain an actuator component integrated with the potentiometer.

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    \$\begingroup\$ This is mostly incorrect. A potentiometer would only be the actuator in a heater if the potentiometer itself got hot. And there's no requirement for signal processing components to be classified as either sensors or actuators. The definition is simply whether it directly measures something (sensor), directly produces a physical action (actuator), or neither (everything else). \$\endgroup\$ – Graham May 24 at 18:05

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