dual potentiometer wired in parallel

Question

I'm trying to understand if those two circuits are 100% equivalent.

I mean, if I use a dual gang 100K linear potentiometer, and wire it like VR1A-VR1B, do I get a single potentiometer exactly like VR2 (50K linear)? is the same true with the presence of R1/R2, as shown on the picture?

Trevor_G · Answer 1 · 2017-04-26T17:03:33.800

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Electrically yes they are. The ganged one can withstand a lot more power than the single, but that would not be an issue with the subsequent resistor values shown.

Mechanically though it would reduce wiper noise. That is, the effect of dead spots as the wiper moves across the resistor. Often heard as a LOUD crackle on audio systems as you adjust the volume. However, in parallel with 120K you would still see a significant voltage change when one or the other was on a dead spot.

edited Apr 26 '17 at 17:03

answered Apr 26 '17 at 16:57

Trevor_G

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Another related effect: Its easier to deal with dead spots because you can always generate the same total parallel resistance with an unlimited number of related wiper positions. – Cort Ammon Apr 26 '17 at 17:55

Spehro Pefhany · Accepted Answer · 2017-04-26T17:41:16.177

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Pretty close. Probably the CRV (contact resistance variation) will be reduced in the ganged version, and power dissipation capability may be different for different constructions, but those are minor points.

With the given circuit the maximum power dissipation is negligible compared to the capability of most any pot you can think of unless the loose end of that 120K resistor gets connected to some absurdly high voltage.

CRV reduction would be more of a factor on a low resistance cermet pot where it is typically specified as the larger of a percentage of element resistance or a certain number of ohms.

edited Apr 26 '17 at 17:41

answered Apr 26 '17 at 14:58

Spehro Pefhany

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The CRV shouldn't be reduced in this wiring, they're perfectly parallel. – Oskar Skog Apr 26 '17 at 17:03
@OskarSkog If the CRV limit is expressed as a percentage of element resistance then it should be similar, as you say. – Spehro Pefhany Apr 26 '17 at 17:24

score 3 · Answer 3 · answered Apr 26 '17 at 14:27

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Short answer, yes. Potentiometers act exactly like resistors, so ask yourself, if you put resistors in place of the pot, would the equivalence hold?

answered Apr 26 '17 at 14:27

Hearth

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Resistors with the values x*p and x*(1-p), where p is the position in the range 0...1 and x is the resistance of the potentiometer. – Oskar Skog Apr 26 '17 at 17:02

dual potentiometer wired in parallel

3 Answers3