Difference Between DCS and PLCs

Programmable Logic Controllers (PLCs) are suited for smaller-scale operations because Distributed Control Systems (DCS can have a larger geographical spread. DCS and PLCs are becoming increasingly similar as their advances try to eliminate the disadvantages of each system. 

Are you trying to determine the difference between PLCs and DCS? Are you weighing the pros and cons of each type of automation control? Keep reading to learn more about the differences, disadvantages, and benefits of each type of automation control.

This AI Automation blog post will spell out the differences between PLCs and DCS. You’ll be prepared to talk to your automation contractor about what type of Industrial Control System (ICS) and automation technologies are best for your company’s needs. 

If you’re still on the fence about automating your company’s processes, learn more about the Pros and Cons of Industrial Automation.

Distributed Control System vs. Programmable Logic Controllers

Distributed Control Systems (DCS) are most widely used for continuous processes, but Programmable Logic Controllers (PLCs) are more commonly used for discrete processes. As the technology of both control systems improves, the technologies become more similar than different.

What is a Distributed Control System (DCS)?

A distributed Control System (DCS) is a connection of central processing units (CPUs) that monitor and control automated processes. DCS was designed to replace DDC (Direct Digital Control). DCS hardware and software is usually sold as a package and has limited flexibility.

What is a Programmable Logic Controller (PLC)?

A Programmable Logic Controller (PLC) is an industrial computer that receives inputs and is programmed to dictate the response. PLCs are paired with custom sensors and equipment to tailor the programming to the needs of the automated process. 

Differences Between DCS and PLCs

Distributed Control Systems (DCS) have the ability to manage larger operations than Programmable Logic Controllers (PLCs). PLCs are capable of faster processing times and are more customizable when compared to DCS.

Similarities between DCS and PLCs

Newer PLCs are becoming more powerful and sophisticated to gain some of the advantages of DCS, including reliability. DCS is becoming more nimble and adaptable to gain some of the advantages of PLCs. With time, the similarities are increasing, and the differences are decreasing.

PLC Benefits and Disadvantages

Programmable Logic Controllers (PLCs) are an integral part of of automation and industrial control systems because of their flexibility and ease of programming. They have the disadvantage of not being able to control processes in a decentralized way like DCS.

Many automated processes that rely on DCS still rely on PLCs are local points in the system, so using these technologies doesn’t have to be exclusively one or the other. Find a reliable PLC programmer for customized advice.

Here are lists of the pros and cons of using PLCs:

PLC Benefits and Advantages

  • PLCs have more flexible programming than alternatives because PLCs are blank slates that can be connected to custom sensors and programmed to perform needed tasks.
  • PLCs are much more efficient than the relays they replaced.
  • PLCs can be connected to customized sensors.

PLC Drawbacks and Disadvantages

  • PLCs can be less reliable than DCS because they have fewer redundancies.
  • PLCs have a limited geographical area of effectiveness.
  • You have to write and define the functions of the PLC yourself.

Keep reading to learn more about the pros and cons of PLCs here.

DCS Benefits and Disadvantages

Distributed Control Systems (DCS) are more reliable than PLCs because of the built-in redundancies and decentralized capabilities. However, the whole system has to be configured, including hardware and software, so DCS is less flexible and more expensive than PLCs.

Here are lists of the pros and cons of using DCS:

DCS Benefits and Advantages

  • The decentralized design of DCS allows for processes to be controlled and monitored over a larger geographical area than PLCs.
  • DCS is designed with redundancies so that if one central processing unit (CPU) fails, it doesn’t disrupt the entire process.
  • DCS can be used in combination with PLCs to reap the benefits of both technologies where needed.
  • DCS comes with some predefined functions and function blocks.
  • DCS has the option of using higher-level programming languages.

DCS Drawbacks and Disadvantages

  • DCS systems are less customizable than PLC systems because the hardware and software have to be ordered as a preconfigured package with particular sensors.
  • DCS is more expensive than PLCs.
  • DCS has a slower response time than PLCs because of the complexity of the programming, increased processing loads, and wider geographical spread.

PLC Programming Services

Whether you want to use DCS or PLCs, it’s important to find a reliable contractor to install or update your systems. AI Automation offers industrial automation services like PLC programming in Fresno, Stockton, Modesto, and the surrounding areas in California.

Contact Access Industrial Automation online or by calling (209)-577-1491.

Frequently Asked Questions

Which one is faster: PLC or DCS?

Programmable Logic Controllers (PLCs) have a faster response time to inputs than Distributed Control Systems (DCS). However, some proponents of DCS would say that the overall efficiency of using DCS is better than with PLC.

What are the drawbacks of DCS?

The drawbacks of DCS include the decreased processing speed. The DCS is slower to respond because of the complex processes required to operate the system. DCS tends to be less customizable than PLCs, and the DCS software and hardware packages are more expensive.

Can you connect PLCs to DCS?

Programmable Logic Controllers (PLCs) can be connected to Distributed Control Systems (DCS) where needed using communication protocols.

What languages does DCS use?

Distributed Control Systems (DCS) use the following programming languages: ladder logic (also called ladder diagram), instruction list, structured text, sequential function list, and functional block diagram. DCS may also use a more complex language called continuous function chart. 

What languages do PLCs use?

Programmable Logic Controllers (PLCs) use low-level programming languages like ladder diagram (also called ladder logic), instruction list, sequential function list, functional block diagram, and structured text.

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