Attach is a circuit I built in Multisim 9 to emulate the log
The key component for this circuit is the voltage control
resistor which you can find this in the basic virtual library. The DC source on the far left is to emulate
the wiper position.The other DC source is
to emulate the pot resistance, in this example 10V represent a 10K pot.Basically, the wiper DC source feed into a
non-linear control voltage source which contains log (VIN) equation.From
the non-linear source it controls one side on the pot.The other side is control by the Adder which
is 10V-output of the non-linear source.If you use an ohm meter should measure the resistance on the other side.