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For example, I have a 10k ohm (linear) Thumbwheel Potentiometer. This POT will produce values from 0 to 10k when reading its resistance.

Positive Shift

  • How do I shift resistance range values by X ohms in the positive direction? E.g. a 10k POT will yield a new range of: 10 to 10,010 ohm, shifted by 10 ohms?

    enter image description here

Since I am using an Arduino, I could programmatically scale the resistance value. But I do not want to do that.


Negative Shift

  • How do I shift resistance value range by X ohms in the negative direction? E.g. a 10k POT will yield a new range of: -10 to 9990 ohm, shifted by 10 ohms?
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    \$\begingroup\$ You mean to just add \$X\$ \$\Omega\$ to the resistance? \$\endgroup\$
    – copper.hat
    Feb 9, 2015 at 16:21
  • \$\begingroup\$ Yes, to shift the range? \$\endgroup\$
    – lucidgold
    Feb 9, 2015 at 16:56
  • \$\begingroup\$ @lucidgold, point is, is X always positive, or do you want a solution for negative X also? \$\endgroup\$
    – The Photon
    Feb 9, 2015 at 16:59
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    \$\begingroup\$ How do you intend on using a resistance of -10 ohms? \$\endgroup\$
    – Greg d'Eon
    Feb 9, 2015 at 17:51
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    \$\begingroup\$ As you have drawn the connections, you are not using the potentiometer as a variable resistance, but as a variable voltage. The analog input to the Arduino draws almost no current, causing almost no voltage drop on any resistor you put on the middle terminal, so it won't have any effect. Remember that the analog input reads voltages, not resistance. Do you want to shift the voltage by a certain amount? \$\endgroup\$
    – Austin
    Feb 9, 2015 at 23:30

1 Answer 1

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If you want to have your potentiometer going from 10k to 20k, simply hook a 10k after the potentiometer (e.g. where you get your changed Voltage).

Formula: Potentiometer range: From x to 10k+x: Add a resistor of x to the potentiometer. If you want to extend the range, then you have to use another approach.

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  • \$\begingroup\$ In other words, put it in series. \$\endgroup\$
    – Jeff Bell
    Feb 9, 2015 at 16:45
  • \$\begingroup\$ @JeffBell: Got it, is my diagram correct? \$\endgroup\$
    – lucidgold
    Feb 9, 2015 at 16:59
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    \$\begingroup\$ @lucidgold - nope. Connect it to one end or the other. If the pot is to be used with one end tied to ground, add the resistor between the pot and ground. \$\endgroup\$ Feb 9, 2015 at 17:00
  • \$\begingroup\$ @WhatRoughBeast: Alright, so this POT has 3 pins. Using the Arduino I can read the resistance value from the middle pin. You are suggesting I connect the 10ohm resistor to GND pin (from POT)? \$\endgroup\$
    – lucidgold
    Feb 9, 2015 at 17:02
  • \$\begingroup\$ If you want to lift the pot's range above ground, you put a resistor between ground and the counterclockwise terminal, not on the wiper terminal. \$\endgroup\$ Feb 9, 2015 at 17:04

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