Hello, 

I was wondering if anyone new the difference between Rheostats and Potentiometers ? I found this article that explain it a bit Rheostat Explanation  but doesn't go into detail . I was wondering if anyone might know? 

Reason I am asking is the rheostat broke in my control module for my flight simulator , I was going to replace it. But only can find potentiometers as replacement parts not rheostats.

Any and all info / help would be great !

Welcome to the AVSIM forums!  😃

The potentiometer is a three terminal device used for voltage control, while the rheostat is a two terminal device used for current control. Then the potentiometer, trimmer and rheostat are electromechanical devices designed so that their resistance values can be easily changed.

If you take a potentiometer and connect just the central and one of the side terminals it will work as a rheostat (Wiki). Honestly speaking I seriously doubt that the part in question in your device is really a rheostat; I'd bet that it's a potentiometer connected as a rheostat.

At this point it would be great to get more details about your control module and the part in question; preferably with photos.

Edited January 7, 20215 yr by SergeyPe

If you use a varistor/rheostat, you need to know the load resistance in order to select a device range that will produce the desired range of output voltages across the device's resistance range.  If the load resistance varies, so too will the output voltage, as it's a function of Ohm's law. 

With the potentiometer (voltage divider) config, you can vary the output voltage from zero to the full supply voltage without much regard to the load resistance.

In practice, for very high-impedance, low current control circuits like a flight control axis, the simpler rheostat config can often be used, as the load resistance (the A-D converter) remains effectively constant and is relatively very large as compared to the rheostat's resistance.  It sounds like that's how your device is presently configured.  The key to replacing the stock transducer is to find a pot with a max resistance similar to your present device, and connect one lead to the wiper, the other to the appropriate end of the resistive element (depending on which direction of movement you need to increase the resistance/decrease the voltage).  Most of the ones I've played with used 0-100K Ohm pots.  A smaller range can also work, but with some loss of resolution.  And make sure it's a *linear* pot--the ones commonly used in audio volume control circuits are logarithmic scale devices...that won't work well as a joystick axis transducer.