d(rc)/d(pos) = k d(pos).
The constant k is expressed in terms of the rangeability, i.e., the ratio between the maximum and the minimum useful flow coefficient:
rangeability = exp(k) = rc(1.0)/rc(0.0).
The theoretical characteristic has a non-zero opening when pos = 0; the implemented characteristic is modified so that the valve closes linearly when pos < delta.
function equalPercentage extends baseFun; input Real rangeability = 20 "Rangeability" annotation( Dialog); input Real delta = 0.01 annotation( Dialog); end equalPercentage;