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Resistance Reading on variable resistor

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Newbie level 1
Oct 28, 2009
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This should be pretty simple but I put together a circuit that calls for an adjustable resistor (pot) and I was wondering if there was some way to output the current value of the POT to the user without affecting the actual value. What all would I need and how should I set it up? Thanks

Jasonb61 said:
output the current value of the POT to the user without affecting the actual value.
Sorry...I didnt understand the term. Could you please explain in detail a bit? Cheers

You could find a dual-track pot compatible with the one you're currently using, wire up one track as normal to your circuit requiring the variable resistance, and wire up the second track to a sensing circuit.

If that's not an option, would using a digital pot be viable? If you keep track of the control signals sent to the pot, you'd know on which tap the wiper was positioned, and thus be able to calculate a resistance value. It wouldn't be a direct measurement, but depending on what sort of accuracy you require it may be good enough.

Alternatively, depending on your application you may be able to stick a current sense resistor in series with the pot, measure the current through the pot, and do a quick R=V/I calculation...

On a similar vein, you may be able to sense the voltage at the wiper terminal and determine the wiper position/resistance value from that.

Alternatively alternatively, you could either try to find, or bodge one together yourself, a pot which includes some form of positioning feedback - e.g. a slotted disk/photosensor setup attached to the pot spindle - so you could detect any motion of the wiper and infer the pot position/value from that.

If all else fails and you don't need the result presented electronically, then perhaps a mechanical approach will suffice - stick a pointer on the pot spindle, stick a scale marking around the pot, and let the user read off the value manually...

Basically, there are many options (including all the ones that didn't spring to mind whilst writing the above) for determining the position/value of a pot, choosing which one to use is then down to how the pot is being used in your application, and in what form you want to present the result to the user.

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