Regulator on DCS
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How can one quickly determine whether a regulator is positive or negative acting?
By observing the input and output, it is possible to determine quickly whether there is a positive effect: when the deviation increases, that is, when the input increases, the output also increases; whereas in a negative effect, the output decreases as the input increases.
By observing the input and output, it is possible to determine quickly whether there is a positive effect: when the deviation increases, that is, when the input increases, the output also increases; whereas in a negative effect, the output decreases as the input increases.
Ensure negative feedback for a single loop. For example, in a single-loop flow system, when the valve opening increases, the flow rate increases; in such a case, the regulator should be selected with reverse action. If, on the other hand, the flow rate decreases as the valve opening increases, then a regulator with positive action should be used
The set value can be adjusted for observation. When the set value is increased (which means the deviation suddenly increases), by observing the PV values, an increase in the input results in an increase in the output (an increase in the valve opening), which is known as direct action; whereas an increase in the input leads to a decrease in the output, which is known as reverse action.