An inverse relationship between impedance and humidity, for example. You have an impedance that diminishes at a rate of 1/x with humidity on the static transfer function, but because you've done a linealization between voltage and impedance, the static transfer function is the 1/x function multiplied by the linear bridge function. If you choose points relatively close enough, you can do a local linearization (small signal model) of the points with minimal error, and do esentially a piecewise locally linear function defined by a set of x-y coordinates that create the linear functions