#### Re: Risetime calculator (in tekwiki)

Albert Otten

On Sun, Jan 19, 2020 at 07:54 PM, Roy Thistle wrote:

Hi Albert:
Though it has been mentioned... I think because the pot scales are marked off,
linearly... one needs to use log tapered pots (math won't change, unless you
add in the function(s) necessary to express resistance as a function of shaft
rotation.)
Best wishes and regards
Roy
I'm not sure I understand what you mean Roy. The x in my story is linear in the rotation angle, linear but rescaled to run from 0 (fully ccw) to 1 (fully cw). Of course you can avoid the angle in the expressions when you call the pot parts say R1 (top) and R2 (bottom), with R2 = R - R1. Then in the expressions x has to be replaced by R1/R. You end up with quadratic expressions in R1/R. So the scale has to be linear function of R1/R, otherwise you would not get a quadratic function in the scale reading. The easiest way to draw the markings is linear in angle, which only applies when the pots are linear.

Albert

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