At 02:34 PM 11/29/2015, you wrote:
>Cheap log pots, according to my measurements, are two linear sections.    =
0
>- R/10 at half rotation and R/10 to R at full rotation.  That leads to a
>very noticeable and disturbing discontinuity around the mid point.
>I also often wonder why they are called "log" pots when their  law is
>actually exponential?

You'd normally use it as a voltage divider,

With your R0/10 at 0.5 rotation (other curves such as R0/5 @ 0.5 rotation
are available), the ideal exponential equation for the resistance R to
the CCW terminal is:

R =3D (1/80) R0 * (exp(k * a) - 1)  where  0<=3Da<1 is the pot rotation
and k =3D ln(81) ~=3D 4.39 is a constant.

So, the output ratio of R/R0 .. the voltage you'd get with a voltage divide=
r..
is (sort of) logarithmic with wiper position a:

ln((R/R0)*80) =3D k * a -1


--sp




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