Implementing stepwise regulation in PLC

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I would like to ask: there are two valves, one large and one small, used to maintain stable flow (pressure). The design involves using two AO outputs from the PLC, providing signals of 4–20 mA, which are sent to these two valves. So, how should the PLC program be written? Is it to call a PID and then distribute its output range of 0~100% between two AO devices? (For a PID output of 0~50%, the valve with a smaller opening range operates at 4~20mA; for a PID output of 50~100%, the valve with a larger opening range operates at 4~20mA.) In other words, when the PID output is less than 50%, the valve with the larger opening range is fully closed, while the valve with the smaller opening range is adjusted ； When the PID output value > 50%, is the small valve fully open and the large valve regulated? Thus, it remains to be seen whether this set of PI parameters can meet the requirements.