Abstract: A control system for maintaining the liquid levels in a plurality of reservoirs connected in series includes one or more nested control modules. The nested control module, one for each reservoir, includes a proportional only level controller in electrical communication with the respective level sensor of each respective reservoir and is adapted to produce an output that becomes a set point for one or more respective PID flow controllers adapted to control the respective outflows of said respective reservoirs. The control system results in maintaining liquid levels in the reservoirs while substantially eliminating flow and level oscillations.

Abstract: A control system for maintaining the liquid levels in a plurality of reservoirs connected in series includes a parenthetical control module and one or more nested control modules. The parenthetical control module includes a proportional only level controller in electrical communication with the level sensor of said last reservoir (VOUT) in the series and is adapted to produce an output signal that becomes a set point for one or more PID flow controllers controlling the inflow (FIN) into the first reservoir (V1) in the series. The nested control module, one for each reservoir upstream of said last reservoir (VOUT), includes a proportional only level controller in electrical communication with the respective level sensor of each respective upstream reservoir and is adapted to produce an output that becomes a set point for one or more PID flow controllers adapted to control the respective outflows of said respective upstream reservoirs.