What are the differences and connections between the forward and reverse actions of a regulator and those of a valve positioner?
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RT for help: What are the differences and connections between the forward/reverse action of a modulator and that of a valve positioner?
In my understanding, the positive or negative action of a regulator refers to the signal that the regulator sends to the control valve based on the difference between the data provided by the system and the data measured on-site; if the difference is positive, it’s positive action, and if it’s negative, it’s negative action. As for the positive or negative action of a positioner, it relates to the control valve – positive action of a positioner generally means that the valve opens, that is, it operates in response to air pressure or for emergency shutdown purposes, while negative action means that the valve closes under normal conditions but opens in emergency situations. Anyway, it is the data from the regulator that is sent to the positioner, which then uses this information or signal to control the action of the control valve. This is my understanding; I hope it can be supplemented
The forward and reverse action of the positioner corresponds to the air-open and air-close operation of the control valve you have selected. In other words, it is designed to achieve negative feedback for the valve as a whole. The positive and negative actions of the regulator are designed to provide negative feedback for the entire control loop; it is only when the regulator is set to automatic mode that the effects of these positive and negative actions become apparent.
The positive and negative action of a valve positioner is determined by whether the control valve operates in open or closed mode; the positive and negative action of a regulator is determined by the characteristics of various components in the control loop. It is necessary to ensure that the control loop meets the required control specifications, such as enabling negative feedback control.
The entire circuit forms a closed-loop negative feedback system; both the regulator and the valve’s reactive actions take place within this closed loop, being part of it