Logarithm Function Generated by Parallel Resistors
Daniel Steinmeyer · IEEE Transactions on Computers · 1969
Placing a fixed resistor in parallel with an adjustable resistor will cause the resistance of the combination to vary as the logarithm of the setting of the adjustable resistor over a limited range. Calculated compromises between accuracy and range cover ±0.1 percent over a 2.5:1 range to ±10 percent over a 175:1 range. A table of intermediate values is given.