ControlEngineer

I have one question about loop control as I attach two pictures. There are two types of control; the single loop control and the multi loop control. In the single-loop control there are two valves which should be controlled; the one is the heating valve, the other is humid valve. In the multi-loop control there are three valves which should be controlled; the one is the heating valve, the other is the humid valve and the third is the cooling valve. how can I control the valve in these each cases and what is the exact different between single loop control and multi loop control? Thanks.