PLC & PID Control: What’s Right for Your Industrial Automation Process

A common misconception that arises from time to time is a misunderstanding of the relationship and function of Programmable Logic Controllers, or PLC, and Proportional Integral Derivative Controllers, PID controllers.

These two systems will monitor and control industrial automation; however, it is often assumed that both systems can perform the same function. Although this is true in some instances, the output quality can differ significantly where precision and quality control are required.

So, what’s the difference between a PLC & a PID controller?
 

PLC: Programmable Logic Controllers

Programmable Logic Controllers are typically found as an overseeing control system within an industrial automated process.

Programmable Logic Controllers (PLCs) are fundamentally designed to be discrete control systems comprised of a limited number of states for inputs and outputs. For the most part, PLCs effectively operate under a set of on and off states.

There are often two different types found in operation:

• Fixed/Integrated/Compact PLC
• Modular PLC

Fixed/Integrated/Compact PLCs often have a fixed range of input/output options. The Modular PLC allows users to add or reduce the range of input/outputs as needed.

Generally speaking, PLC controllers commonly manage larger industrial automated systems. For example, a bottling plant oversees many tasks, including filling bottles, applying labels, and packaging into boxes. Each stage of the plant provides a yes or no response to the PLC, allowing or disallowing the process to progress to the succeeding stage.

PID: Proportional Integral Derivative Controllers

Proportional Integral Derivative controllers take a far more granular approach, focusing on a specific segment within a process to ensure a consistent result. PID controllers do this by taking feedback from sensors, such as thermocouples, and adjusting the process to ensure the programmed setpoint parameters are met with each batch.

Take a biscuit factory, for example. Biscuit production lines often require precise temperature requirements for food regulation and quality control.

For the perfect biscuit, precise temperature control is key. 

An undercooked biscuit may leave for a softer centre, often leading to the biscuit crumbling at the packaging phase. Crumbling isn’t a problem for one or two biscuits, but entire product batches of biscuits crumbling would likely have a significant impact on dissatisfied customers.

However, at the opposite end of the spectrum, an overcooked biscuit can negatively affect the end customer. The biscuit may be too hard or rigid for the customer to consume, or even discolouration from caramelisation can be off-putting.

It’s not that biscuit customers are fickle; it’s that a good-quality biscuit is created within the harmony of precise temperature control provided by PID loop controllers!

For consistent quality control, a biscuit production tunnel oven will require pairs of thermocouple probes installed on each baking zone. The probes will continuously communicate the zone temperature to the PID controller, which will self-adjust the oven temperature settings to match the programmed setpoints.

To learn more, visit our range of  Proportional Integral Derivative Controllers, here. 

To learn more about Watlow Thermal Control Solutions.

To learn more about Eurotherm Process Control Solutions.

The Right Tool for the Right Task

As mentioned above, PLC and PID control systems have been known to perform the same task occasionally but with wavering results, impacting resources, time management, and the end user.

However, as technology has advanced, industrial automation process technologies have begun integrating aspects of both control systems into the same device. Some PLCs provide users with limited PID loop control, and other PID controllers provide users with limited PLC control. 

In this instance, ADM Systems can use a process automation controller, or PAC for short, to cater to users with such needs.

Process Automation Controllers 

The Process Automation Controller may provide the ideal combination of PLC functionality and high-accuracy PID Loop Control. It also includes coverage with redundant central processor units, CPU, various programming languages, and the ability to incorporate advanced control strategies.

To learn more, visit our Eurotherm PAC T2750.

Let us help you find the right tool!

Investing in the right PLC and PID control system can make all the difference in creating quality in your production, saving materials and time, and providing customers with a consistent and reliable output.

But we know it can still be tricky to decide where and which options best suit your production needs. Don’t worry; the experienced ADM Instrument Engineering team is here to help.

Call the team on 1300 236 467 or send an enquiry via our contact page.