Potentiometer Joystick
This is the classic proportional control lever that measures lever angle with a wiper sliding over a resistive track. It is a cheap and simple solution; however, because the track and wiper rub against each other, it wears over time, and in the worn region the signal starts to jump and the center point drifts.
The construction is simple: a fixed voltage is applied across the two ends of the resistive track, and the voltage taken from the center terminal varies proportionally with lever angle. The signal produced is generally between 0-5 V or 0-10 V.
- The most common fault is track wear in the most-used region; as the lever passes that point the motion cuts out for an instant or jumps.
- Dust and moisture change the resistance on the track, so the signal becomes noisy; a small amount of filtering in the controller is essential.
- To distinguish a broken wire, values approaching the ends of the supply range are interpreted as a fault.
Diagnosis in the field is easy: sweep the lever slowly end to end while measuring the signal, and if you see a jump or dropout the track is worn. Because service life expectancy is low on machinery with heavy vibration and dust, switching to levers with non-contact sensing is the safer choice in critical applications.
Where this term is used: The Importance of Hydraulic Control: Why Should It Be Commanded by an Electronic Signal?