## Dead Time Is The “How Much Delay” Variable

Step 3 of our controller design and tuning recipe is to approximate the often complex behavior contained in our dynamic process test data with a simple first order plus dead time (FOPDT) dynamic model. In this article we focus on process dead time, Өp, and seek to understand what it is, how it is computed, […]

## Process Time Constant is The “How Fast” Variable

Step 3 of our controller design and tuning recipe is to approximate the often complex behavior contained in our dynamic process test data with a simple first order plus dead time (FOPDT) dynamic model. In this article we focus on process time constant, Tp, and seek to understand what it is, how it is computed, […]

## Process Gain Is The “How Far” Variable

Step 3 of our controller design and tuning recipe is to approximate the often complex behavior contained in our dynamic process test data with a simple first order plus dead time (FOPDT) dynamic model. In this article we focus on process gain, Kp, and seek to understand what it is, how it is computed, and […]

## Step Test Data From the Heat Exchanger Process

A previous article presented the first order plus dead time (FOPDT) dynamic model and discussed how this model, when used to approximate the controller output (CO) to process variable (PV) behavior of proper data from our process, yields the all-important model parameters: ▪ process gain, Kp (tells the direction and how far PV will travel) […]

## Sample Time Impacts Controller Performance

There are two sample times, T, used in process controller design and tuning. One is the control loop sample time that specifies how often the controller samples the measured process variable (PV) and then computes and transmits a new controller output (CO) signal. The other is the rate at which CO and PV data are […]

## Process Data, Dynamic Modeling and a Recipe for Profitable Control

It is best practice to follow a formal procedure or “recipe” when designing and tuning a PID (proportional-integral-derivative) controller. A recipe-based approach is the fastest method for moving a controller into operation. And perhaps most important, the performance of the controller will be superior to a controller tuned using a guess-and-test or trial-and-error method.

## The Components of a Control Loop

Components of a Control Loop A controller seeks to maintain the measured process variable (PV) at set point (SP) in spite of unmeasured disturbances (D). The major components of a control system include a sensor, a controller and a final control element. To design and implement a controller, we must:  1) have identified a process […]

## Motivation and Terminology of Automatic Process Control

Automatic control systems enable us to operate our processes in a safe and profitable manner. Consider, as on this site, processes with streams comprised of gases, liquids, powders, slurries and melts. Control systems achieve this “safe and profitable” objective by continually measuring process variables such as temperature, pressure, level, flow and concentration – and taking […]