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I notice that the mechanical life of some trimpot potentiometers specified in unit "cycles". But what "cycle" exactly mean?

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  • \$\begingroup\$ Link to datasheet? \$\endgroup\$
    – Transistor
    Sep 10, 2017 at 12:01
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    \$\begingroup\$ I would assume a cycle means rotating the wiper from one end to the other and back. But, I don't have a reference to back it up so no answer. \$\endgroup\$
    – JRE
    Sep 10, 2017 at 12:12
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    \$\begingroup\$ A cycle means "one move forth and back" on whichever strip of the potentiometer used. Most potentiometers aren't trimmed back and forth the whole strip but the thing is still broken as soon any spot on the used part has reached the limit. \$\endgroup\$
    – Janka
    Sep 10, 2017 at 12:41
  • \$\begingroup\$ @Janka - Since you believed my answer was misleading, I've deleted it as I don't want to mislead anyone. I hope someone can provide a better one. \$\endgroup\$
    – SamGibson
    Sep 10, 2017 at 13:26
  • \$\begingroup\$ I had hoped you would add some more information instead – did not downvote. \$\endgroup\$
    – Janka
    Sep 10, 2017 at 14:08

2 Answers 2

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Test condition most certainly is moving forth-and-back the whole strip because that's the way the wiper has most wear.

But for any application, a cycle means "one move forth and back" on whichever strip of the potentiometer used. Most potentiometers aren't trimmed back and forth the whole strip but the thing is still broken as soon any spot on the used part has reached the wear limit.

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    \$\begingroup\$ "the thing is still broken as soon as any spot on the used part has reached the limit" Its not like the pots count turns and break exactly at n cycles. The limits are generally minimum cycles. The devices aren't guaranteed to work past that number but they very likely will continue to work but could soon fail. Its unclear if by "wear limit" you mean the datasheet number or the point where an individual device fails. If the former, you are wrong, if the latter, its a bit of a tautology. \$\endgroup\$
    – Matt
    Sep 10, 2017 at 22:19
  • \$\begingroup\$ I'm not focusing on the individual devices vs. the whole lot but on the moving of the wiper. It doesn't matter how far the wiper is moved. One broken spot means the device is broken. \$\endgroup\$
    – Janka
    Sep 10, 2017 at 22:48
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From a Vishay application note on potentiometers and trimmers:

2.6 - Rotational life

The minimum number of cycles of operations obtainable under specified operating conditions while product remains functional. A cycle is defined as the travel of the moving contact on the resistance element, and back on 90 % of the effective electrical travel.

Note: the test conditions may vary from manufacturer to manufacturer.

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