Process Engineering Division – Instrumentation and Automation Section – Daily Topics – Topic No. 2020-12-29

Actuator forward and reverse actions, namely air-open and air-close； Positive or reverse orientation of the valve core: in the correct orientation, the valve core moves and the flow capacity increases; in the reverse orientation, the flow capacity decreases ； Taken together, if the actuator is in the positive position and the valve core is also in the positive position, then the entire valve operates in the positive direction; if the actuator is in the negative position while the valve core is still in the positive position, then the entire valve operates in the negative direction; if the actuator is in the positive position but the valve core is in the negative position, then the entire valve operates in the negative direction; finally, if the actuator is in the negative position and the valve core is also in the negative position, then the entire valve operates in the positive direction.

Actuator forward and reverse actions, namely air-open and air-close； Positive or reverse orientation of the valve core: in the correct orientation, the valve core moves and the flow capacity increases; in the reverse orientation, the flow capacity decreases ； Taken together, if the actuator is in the positive position and the valve core is also in the positive position, then the entire valve operates in the positive direction; if the actuator is in the negative position while the valve core is still in the positive position, then the entire valve operates in the negative direction; if the actuator is in the positive position but the valve core is in the negative position, then the entire valve operates in the negative direction; finally, if the actuator is in the negative position and the valve core is also in the negative position, then the entire valve operates in the positive direction.

The positive or negative nature of the regulator can be determined based on the controlled object and negative feedback: when PV > SV, MV needs to be increased, which indicates that the controlled object is negative and the regulator is positive, resulting in negative feedback; when PV > SV, MV needs to be decreased, which indicates that the controlled object is positive and the regulator is negative, also resulting in negative feedback.

My simple understanding: Positive effect: When the regulator’s output increases, the parameters of the controlled object also rise. Reaction: When the regulator output increases, the parameters of the controlled object decrease.

A regulator is a controller that compares the measured values of process parameters with set values; once a deviation is detected, it generates an output signal in accordance with certain control rules to actuate an actuator and eliminate that deviation, thereby keeping the parameter within close to the set value or causing it to change according to a predetermined pattern. When the controlled parameter (i.e., the signal sent by the transmitter) increases, and the output of the regulator also increases, this is referred to as positive action; whereas when the controlled parameter increases, the output of the regulator decreases, which is known as negative action. Or, when the controlled parameter (i.e., the signal sent by the transmitter) decreases, the output of the regulator also decreases; this is known as direct action. When the controlled parameter (i.e., the signal sent by the transmitter) decreases, the output of the regulator increases; this is known as reverse action.

When the controlled parameter (i.e., the signal sent by the transmitter) increases, and the output of the regulator also increases, this is referred to as positive action; whereas when the controlled parameter increases, the output of the regulator decreases, which is known as negative action.

This post was last edited by Ku Liang Zhi Le on 2020-12-29 at 10:49. The purpose of properly setting the forward and reverse actions of the controller is to ensure that negative feedback is established in the circuit. There are two definitions for the forward and reverse actions of a controller: one is the instrument definition, and the other is the system definition. Definition of the instrument for the controller’s positive and negative reactions: The system definition for the controller’s positive and negative reactions is E=R-Z; it differs from the instrument definition by a negative sign. Some manufacturers have recognized this issue and unified the two definitions into a system-defined one; for example, in Siemens’ PCS7 system, the forward and reverse operation of the controller are defined based on the system standards.

Positive action of the regulator: When the controlled variable is higher than the set value, the output signal of the regulator increases, which is known as positive action. Regulator reaction: When the controlled variable is above the set value, the regulator’s output signal decreases, which is known as a reaction.

Positive action regulator: As the controller input signal increases, the output also increases； A regulator in which the output decreases as the input signal increases is called a negative feedback regulator.

A regulator is a controller that compares the measured values of process parameters with set values; once a deviation is detected, it generates an output signal in accordance with certain control rules to actuate an actuator and eliminate that deviation, thereby keeping the parameter within close to the set value or causing it to change according to a predetermined pattern. When the controlled parameter (i.e., the signal sent by the transmitter) increases, and the output of the regulator also increases, this is referred to as positive action; whereas when the controlled parameter increases, the output of the regulator decreases, which is known as negative action. Or, when the controlled parameter (i.e., the signal sent by the transmitter) decreases, the output of the regulator also decreases; this is known as direct action. When the controlled parameter (i.e., the signal sent by the transmitter) decreases, the output of the regulator increases; this is known as reverse action.