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I have been using a trimmer pot (Bourns 3224W-1-104 100k 3224W 4mm 11-turn SMD Trimmer Pot) in a design. The pot does not get adjusted in production and ships with the pot set as shipped from the manufacturer. This has not caused any issues. I’ve measured the value of the pots to be around 30k ohm on a sample of 5 boards.

What I would like to know is - do these parts get shipped from the factory at a defined setting? Can one rely on this always being the same setting? Is this specified in the datasheet?

I’ve noticed one parameter in the datasheet that I’m guessing could be the specified value “ Wiper ........................50 % (Actual TR) ±10 %” but I’m not sure.

I have tried contacting Bourns but not had a response.

I assume that these devices are tested to some degree and if they follow a predetermined process, then the devices should always ship at the same predetermined value.

Thanks in advance

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2 Answers 2

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Unless there's a default specified on the datasheet, or the manufacturer answers and guarantees a default setting and tolerance, you can't rely on a specific default setting from the manufacturer. Test or manufacturing procedures could change at any time, so the default value could change as well. It's up to you if you want to take the risk that they'll always be in an acceptable range for your design based on what you've seen so far in production.

If your pots are measuring 30 k, then the 50% wiper spec on the datasheet isn't likely the default value.

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  • \$\begingroup\$ Thank you for your response John. I was stupidly not considering the fact that I was measuring in-circuit. Turns out the default resistance was around 46k which fits in with the mentioned parameter (50% +/- 10%) in the datasheet. Bourns came back to me and confirmed that the pots ship set at 50k. I’ve never had to consider this so something I have learnt from and I hope it is useful to someone else when designing in a pot. Thanks again! \$\endgroup\$
    – RoyalAce
    May 27, 2023 at 10:28
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Bournes have confirmed the statement in their datasheet:

"“ Wiper ........................50 % (Actual TR) ±10 %”"

means that the part is shipped set at 50% ±10 % of the specified resistance.

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