Is this pot log or lin ?

Well, I need a 100k pot for my mid-boost module (or whatever the reason !). Hey, I found 2 pots in my box. Let see : are they log or lin ?

For sure, they have a code : 100k A for one and 100k B for the other.

Well, well … are these code related to US, Europe, Japan pot ? Are they “old” code or “new” code ? Where the hell is the log pot ?

Most pots have 270 degrees of rotation from one extreme to the other (3/4 turn).

Here are how log and lin pots react (resistance change) when we turn (example of a 100k pot as Y axis, where X axis represents the rotation in degrees)

potentiometer log linSo, it is quite simple to distinguish a log and a lin pot using a simple ohmmeter …

ohmmeter potentiometer

First, let’s use a marker …

potentiometer and markerRotate (for instance anti-clockwise) to an extreme and mark it as it had a knob :

potentiometer marked knob

Take the first pot and measure the resistance :

potentiometer 100k(it’s a 100k pot ;-) )

Then rotate to mid-position and measure again.

Here is the result for a lin pot :

100k lin potentiometer half course(Half course ≈ 50k)

And here is the result for a log pot :

100k log potentiometer half course(Half course ≈ 87k)

These results are consistent with the curves … I know now which pot is log and which is lin !

potentiometer lin log  half course

Hope this helps …

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