What is a PID Controller?

In this video and article, you will learn about PIDs. Specifically, what they are and when do we use them with automation and PLCs.

Today you will learn about PIDs. Specifically, what they are and when do we use them with automation and PLCs.

So what is a PID controller? PID is an acronym that stands for Proportional, Integral, Derivative.

If you need to keep something constant, like a temperature for example, then this is the way to do it.

Essentially, PID Controller uses a control loop feedback to ensure the output wanted is what you will get.

Simply, you put a setting in the controller and it will keep the output constant based on feedback from some input, typically some kind of sensor.

Something you probably encounter every day that is essentially PID control is your cruise control in your vehicle.

First, you get to the speed that you want to be going. Then you set your cruise control. The cruise control sends output signals to your throttle to regulate the speed.

A speed sensor provides your control loop feedback to tell the cruise if the car should speed up or slow down, or how much more or less throttle to provide.

A common standalone type that we use in manufacturing and industry, is a “Temperature Controller PID”.

These controllers are pretty simple to use and setup, plus they do a great job at controlling temperatures of a variety of equipment.

For our example, we will look at a PID controller that controls the temperature of heat tracing on process piping.

First, we need to enter a set point, 200 degrees Fahrenheit for our example.

Now the controller will give a signal to the output to start heating up the heat tracing.

The control loop feedback is in the form of a thermocouple to read the temperature. For our example, the PID controller can work as on-off control for the heat tracing.

Along with the set point of 200 degrees, we will set the controller at a couple of degrees above and below 200 as well.

When the thermocouple reads 202 degrees it will turn the heat tracing off.

When it reads 198 degrees it will turn it back on.

This is the simplest form of PID control.

We also have the option of setting up a PID controller with a PLC. Instead of the standalone unit, we can use the input and output cards already on our PLC.

The process variable, or control loop feedback, would be wired to our input card and programmed into the PID. Our output being controlled is wired to our output card.

The PID in the PLC can do all of the math and make the decisions based on the variables and set points.

No matter which way you decide to set it up, a PID is an excellent choice for an automated process.

In summary, A PID controller is a Proportional, Integral, Derivative controller. It can keep an automated process like temperature, pressure, or flow, constant, for you automatically.

PIDs use a control loop feedback or process variable to monitor where the output should be. These usually come in the form of sensors and meters.

PIDs come in many different forms including standalone units and PLC programming.

We can use our input and output cards along with programming software to set up a PID.

I hope this article really helped you get a grasp of how to use a PID.

Thanks again for reading. Leave your questions and comments and we’ll chat with you soon! 

Happy learning,

The RealPars Team

By Kevin Cope

By Kevin Cope

Instrument Mechanic

Posted on Dec 10, 2018

By Kevin Cope

Instrument Mechanic

Posted on Dec 10, 2018

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