Answer / carl_ellis

Gain, ti and td are PID proportional control tuning terms/constants. PID controllers use PID tuning constants to calculate an output based on the error signal; final control elements (valves) do not do a PID calculation so valves are not involved with gain, ti and td. The controller is typically in the control room, the valve is somewhere out in the process.

A PID controller calculates the expected valve/damper position from the error signal and the tuning constants, the result of which is an output control signal ranging from 0-100%.

A valve positioner or valve I/P receives that control signal from a controller (4-20mA, Profibus) and supplies air or electric power to the actuator to achieve the correct position demanded by the control signal.

Ti is the term for reset or integration. It is used when the process itself is not an integrating process. Level, pressure, and pH are usually integrating processes. Sometimes temperature is an integrating process, sometimes not. When the process is non-self regulating/integrating process, the ti term is not used in the PID calculation.

Flow and temperature processes typically use the ti term for PID calculation.

An exception to the rule of PID being done in a separate controller is Foundation Fieldbus (FF), which allows function block PID execution in FF devices. In a case where PID control is executed in an FF valve positioner, then a valve would use the PID tuning constants.

What is cut off relay? And why use in PLC and DCS?

0 Answers  

---

In which principle Woodward Governor 505 work in power plant? What are the input of Woodward governor 505

1 Answers  

---

what is interface level and how it is calibrate?

0 Answers  

---

what is basic working principle of Governer in power plant?

3 Answers  

---

how can we calibrate RADAR LEVEL transmitter 0% to 100%

3 Answers   Chevron Phillips, Honeywell,

---

---

Rtd sensor how to calibrate

5 Answers   Sepam Group,

---

how to check diode wheather it is working or not by using multimeter?

3 Answers  

---

WHAT IS THE CAM POSITION IN CONTROL VALVE POSITIONER ? WHY IT IS USED?

0 Answers  

---

How flow control valve is working with pnuematic positioner and I/P convreter from command is given from remote

1 Answers   Ecil, GAIL,

---

what is dry leg and what is wet leg?

3 Answers  

---

How to interfacing microcontroller with a DC motor

0 Answers   JJ Tech,

---

control modes

1 Answers   Vedanta,

---