So i ordered this cheap 100 ohm ten turn pot from ebay: Potentiometer

The problem is that it doesn't work as a normal pot (or it is broken).

When i check resistance from pin 2 to pin 3, everything is working fine, i can turn the wiper and the resistance is changing, however, if i check from pin 2 to pin 1, it shows 100 Ohms resistance all the time, no matter how much i turn the wiper. Is it supposed to do that or have i wired it wrong? Thanks!

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  • \$\begingroup\$ Have you tried measuring the resistance between pins 1 and 3? \$\endgroup\$ – John Dvorak Sep 8 '16 at 4:29
  • \$\begingroup\$ @JanDvorak Yes, everything is working fine there. When i turn the pot half the way it shows 50 ohms. \$\endgroup\$ – Xane Sep 8 '16 at 4:30
  • \$\begingroup\$ So, is the pot working just fine except the pins seem mislabeled? \$\endgroup\$ – John Dvorak Sep 8 '16 at 4:31
  • \$\begingroup\$ No.. I mean, if i check one of my other pots i have laying around. Resistance from pin 1 - 2, and from pin 2 - 3 should react the same way. It should not show the max resistance of the pot all the time right? \$\endgroup\$ – Xane Sep 8 '16 at 4:32
  • \$\begingroup\$ In a 'normal' pot, you'd have variable resistance between pins 1-2 and 2-3, and the full resistance between pins 1-3. So apparently this does just what it's supposed to, with only the difference of the order of pins. \$\endgroup\$ – chamod Sep 8 '16 at 4:57

Your pot is probably fine, but the terminal numbering is confusing you. Hopefully this image will make it clear:-

enter image description here

  • \$\begingroup\$ Why should the pins be numbered like that? \$\endgroup\$ – John Dvorak Sep 8 '16 at 5:10
  • \$\begingroup\$ I just tried it! and you where right.. I feel so stupid.. damn ebay stuff who labeles things weird xD Thank you very much Bruce!! :D \$\endgroup\$ – Xane Sep 8 '16 at 5:15
  • 1
    \$\begingroup\$ datasheet confirms: mouser.com/ds/2/54/590-776468.pdf \$\endgroup\$ – Wesley Lee Sep 8 '16 at 5:16
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    \$\begingroup\$ The convention is to number from one end of the track to the other, with the wiper connection on pin 2. But physically this pot has its track spiraling around the inside wall of the body with the wiper in the center, so the wiper connection has to come out the back end rather than between other two terminals. i2.wp.com/www.scienceprog.com/wp-content/uploads/2014/07/… \$\endgroup\$ – Bruce Abbott Sep 8 '16 at 5:22
  • \$\begingroup\$ This is my first time using multi-turn pots, Thank you for the detailed explination! Learned something new hehe \$\endgroup\$ – Xane Sep 8 '16 at 5:24

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