Problem
The purpose of the arrangement shown in FIGURE is to mix the two liquid products A and B in a fixed mass ratio. Product A, which is itself a mixture, is a 'wild' flow, whilst product B, a pure compound, is controlled. As the mixture leaves the tank the transmitter ρTX measures its density.
(a) Complete the diagram to show how the arrangement could be controlled by the method of 'variable ratio control'.
(b) Identify which transmitter provides 'feedforward'.
(c) Describe how the control system responds to a disturbance caused by a variation in the density of product A.
