Many process control systems require redundancy for I/O, controllers, networks, and HMI servers at various levels. Typically, their interfaced … PLC suppliers have been developing new configuration software to provide this level of integration. PLC systems use open published protocols that are designed to cover a wide range of applications including simple discrete, synchronized motion control, motor control, and process. DCS backbone networks are typically standard Ethernet hardware but use their own closed,high-performance protocols and natively support redundancy. Advantage DCS. The controls and automation on a skid become part of the plant just as much as site installed controls and automation. This feature we can not achieved in PLC. DCS versus PLC. When configuring a tag, everything required is there to connect it to a field point and apply alarm logic, history, version control and other functions, saving time and improving quality. Oddly the discrete network interfaces can be an issue with PLC systems since there are many standards and larger vendors optimize the interface and software configuration to their flagship protocols and have weak interfaces to competitive protocols. PLC is mainly used as a controller of processes and mainly comes as a standalone program. In this article the term PLC will include PAC. The majority of process plants today have both DCSs and PLCs installed for controls. ... 3 Comments on “ The Difference Between PLCs and Computers ” Richard says: January 28, … Since the PLC was integrated with Analog I/O it crosses the boundary of being just digital and crosses to the realm of DCS in handling Analogs, Bus Systems, Distributed I/O and etc. In an interview early in 2011 with a business manager at a major PLC company who is pursuing the process business, I asked what distinguishes their offering from a DCS. it's cost is lower than compare to PLC and DCS, it uses profibus and modbus as a communication protocol which are very speedy responds. Although PLCs have become more powerful, they are still based on “loose” component architectures allowing functions to be easily added with hardware and software. What’s difference between PLC and DCS by its definition: PLC is a controller or processor that can be programmed (programmable) whose function is to run (execute) logic functions. DCS systems have for many years provided multi-disciplined controllers for logic, sequential and process control, HMIs, custom applications, and business integration on one platform. Slower processes usually need coordination across varied production units. I have never understood how engineers that would never buy a new automobile without looking under the hood and taking test drives will buy an automation system based on vendor demonstrations and PowerPoint presentations. Skid mounted and packaged systems are factory built units that provide a specific function needed in a plant. As this unfolds, both DCS and PLC suppliers will evolve and we may eventually see a new architecture but in the meantime plants need to continue to operate and improve. These interfaced subsystems generally require more field engineering to configure and maintain than the other plant controls. But as far as concern about the functionlity of DCs and PLC both are same. These other protocol interfaces are typically accomplished with third party interfaces where the software configuration is more cumbersome. I suggest, rather than accepting a suppliers definition of a single unified architecture, that you create a definition for your operations. The difference between distributed control systems (DCSs) and programmable logic controllers (PLCs) can be boiled down to a simple football metaphor. Does the system reduce engineering time for my applications? DDC : DDC is a universal controller where both analog and digital input/outputs are combined in one controller card also it is specially designed for the HVAC ( Heat ventilation air conditioning) design which are used for air handling unit. However, with more powerful PLCs and so-called programmable automation controllers or PACs available today, the line between a PLC and DCS continue to blur. Does the system reduce process control configuration time? Logic means the discrete / sequence function is usually handled by the relay. DCSs were traditionally used to control large processes, while PLC systems were used to control machines. This level of optimization is high level, multivariable control based on real-time business management goals, actual feedstock information, production demand, and energy costs - all in an effort to optimize plant profits. Using same data base server you can edit in logic as well as on graphics screen. This distributed architecture was revolutionary with digital communication between distributed controllers, workstations and other computing elements. In DCS systems, the process networks (Foundation Fieldbus, HART) and PLC-oriented networks (DeviceNet, Profibus, Modbus, etc.) A PLC is a digital computer used to control electromechanical processes, usually in an industrial environment. Posts: 10313. This investment upfront can save a large amount of money and lost production time over the life of a system. Before we get into the differences of a PLC’s and DCS’s, we need to talk about what each of them are designed to do. DCS and PLC have been pillar for control of process plant for quite some time now with advancement in technology. If you produce chemicals, you speak DCS. This is driven by increased unit volume production of processors and related components. The function or intent of traditional PLCs was to provide a stand-alone control system that was economical and very efficient at processing various I/O types. The idea of using a PLC-based system rather than a DCS has become a philosophical and technical debate in the industry. Ideally the plant process control system has efficient and cost effective multiprotocol interfaces for all PLC protocols. Asset management is becoming more important and PLCs are playing catch up with DCSs to provide integrated software for a full range of devices and asset management standards. The DCS supervises the entire process, much like the conductor in an orchestra. DCS configuration uses standard control objects that are automatically linked to the appropriate faceplate, simplifying configuration and leading to standardization. The idea of using a PLC-based system rather than a Distributed Control Systems (DCS) has become a philosophical and technical debate in the industry. PLCs were originally designed to replace relay control systems and their low relevant cost made them ideally suited for production automation and machinery. For example, if you have a two input, one output valve, there is a function block library so you don’t have to create the logic from scratch. Advantage SCADA. For example, a historian may be added to many PLC products by plugging a module into the backplane that acquires data from the controllers, but history communications is done over a separate Ethernet connection. Ten years ago there was a marked difference in the cost of technologies used in DCS controllers and PLCs but with processors, memory, embedded software, and communications commoditization, this has become insignificant for new offerings from all vendors. The first name on the team sheet, your DCS is dependable, hardworking and controls the whole outfit. I understand that the gap in technical capabilities between these 2 breeds of process control systems have narrowed, but still I understand there are some fundamental differences … Concerned about safety? Major worthy advantage of DCS is having centralised database server. if the system has less No. DCSs have been the primary solution for process automation but now many PLC vendors are arguing that a single integrated architecture based on PLCs and/or PACs is the best approach to total plant automation. turn the clock back 10 years: The programmable logic controller (PLC) is king of machine control while the distributed control system (DCS) dominates process control. The main difference between Programmable Logic Controller (PLC) and Distributed Control System (DCS) are: The number of I/O in the system. Process optimization is another area where traditional PLCs may be lacking when compared to a DCS, which will typically offer a number of tools for optimizing control loops and more advanced alternatives to improve performance of PID control. 1) DCS are designed or made available to the user in a way that only configuration in form of a Functional Block has to be carried out unlike PLC, where complete programming has to be implemented using any one of the different languages available in the system. Following this logic, the decision is between the new PLC-based DCS and traditional DCS offerings. Difference between PLC & DCS:- To perform advanced regulative management on a plant-wide scale, DCSs contain the integral infrastructure.Slower processes usually need coordination across varied production units. The PLC control and DCS control system is not a logical level concept. The DCSs generally control and manage the core processes (food, pharmaceutical, refining, etc.). It means PLC is a sub system of a large system called DCS. DCS systems generally have easier to apply redundancy solutions but the open networking standard groups such as ODVA and PI International have defined solutions for their protocols particularly with the initiatives for networked machine safety. He responded by rephrasing the question, noting the real question should be what distinguishes their PLC-based DCS from other DCS systems. PLC-based control systems began to function like a mini-DCS. The premise is this offers the best of both worlds. DCS is mainly used to handle anolog IO's and PLC's for digitaly . Joined: 9/27/2006. This can be accomplished with a demonstration system provided by vendors, including controller hardware. The everyday use of our smart phones, iPads, and electronic games decreases the cost of increased computing power. An advantage often cited by PLC vendors is that all control functions can connect to one Ethernet backbone (process control, discrete, motion control, safety; etc.) Currently there are two main stream types of control systems – PLC-SCADA and Distributed Control Systems (DCS). Of course, the difference in performance between … Last visit: 1/7/2021. As you can see, there are a lot of similarities between the two systems. In a nutshell, a PLC or programmable logic controller is a ruggedized computer used for automating processes. Bosch Rexroth precision modules meet requirements for clean production, Precise miniature slide guides from NB Corporation, The top 10 linear motion articles of 2020, Identifying Best-Value Linear Motion Technologies, Learn how to reduce noise and distortion in encoders’ signals, Helical Planetary Gearboxes: Understanding The Tradeoffs, Tweets from https://twitter.com/Motion_Control/lists/motion-control-tweets. It was the first system to use microprocessors to perform direct digital control of processes as an integrated part of the system. The big advantage was that programmable logic controllers could be reconfigured with software programming rather than rewiring control panels. Does the system support the industrial network interfaces I need now and in the future? Check out our free e-newsletters to read more great articles.. ©2020 Automation.com, a subsidiary of ISA, A subsidiary of the International Society of Automation. Does the system support interfaces to my legacy systems. DCS, or Data Control System, is process oriented, as it focuses more on the processes in each step of the operation. PLC specialist Mart n Hilbers talks about the differences between a PLC-SCADA control system and a DCS configuration. The dilemma is that many skid vendors have typically standardized on one brand and model of PLC controller and the plant is using another vendor. Consider that mobile phone shipments in 2010 were 1.39 billion, up 18.5% from the 1.17 billion units shipped in 2009. When is encoder resolution specified in bits, and what does that tell us? Difference Between PLC & DCS Difference between PLC & DCS :- To perform advanced regulative management on a plant-wide scale, DCSs contain the integral infrastructure. DCS is dealing with very large no. DCS is a relatively large system while the PLC is a small system. The level of controller redundancy for higher level process applications is new to PLC suppliers and they continue to add options for redundancy. "re: difference between plc,dcs&scada" This has been discussed several times, but when I did a search on the site I couldn't locate the threads. also DCS comes with it's SCADA always. if DCS stopped, all system is stopped. The time and cost of integration is significant over the life of a system and should be examined as part of the analysis. Today with open technologies, DCS systems are competitively priced with PLCs. This distinction between the DCS and SIS, led to separate markets for both types of systems with separate suppliers for both, initially. Protocols, like OPC, have eased interactions between the two control systems. Either way, you go, hopefully, this article has shed some light on both the similarities and differences between … I suggest having your own control engineer(s) configure some control loops, sensors, I/O configuration, HMI screens, and communications – specific to your applications - for each system under consideration. C'mon over to https://realpars.com where you can learn PLC programming faster and easier than you ever thought possible! of I/O with less cost. The primary logic offered for using a single PLC-based system rather than a DCS for process functions along with PLCs for discrete functions is to have one control architecture for the entire plant. The system realizes the function and coordination of any device, and the PLC device only realizes the functions of … The DCS from its inception has been designed for configuration as opposed to PLCs which started with a general programming model. All rights reserved. The PLC was invented in response to the needs of the American automotive manufacturing industry primarily to replace thousands of relays, cam timers, and drum sequencers. Rating: (2169) Hello Viana; I would say: Less and less difference every day, now. For instance, PLCs are faster and can handle more complex control. What is a PLC? These PLC vendors are continually demonstrating how their software is like a DCS. So it was easy for engineers to select the one that suits their application, but now due to the advent of microprocessors both the technologies are merging.The requirements which are thought to be exclusive to one technology can be found in the other one … The most significant difference between the two is their general design. Selecting the right system for your operations requires complex analysis, with a number of considerations, based on production processes, in-house capabilities, and other factors. DCS is a kind of Distributed Control System, and PLC is just a (programmable logic controller) controlling “device”, the two are the difference between “system” and “device”. If you manufacture plastic widgets, you speak PLC. PLCs are used to control non-core process functions including material handling, water treatment, motor controls, balance of plant operations, air compressor controls, packaging, and other functions. Real-time software modeling and control optimization is an emerging function being provided to achieve higher efficiencies by DCS suppliers. The material on this site may not be reproduced, distributed, transmitted, cached or otherwise used, except with the prior written permission of WTWH Media. One thing is clear, process users are getting more options to consider. DCS is mainly used as a control system and will feature different processes which can be made up of merged PLC’s. They were initially developed to replace hardwired relays, sequences and timers used in the manufacturing process by the automation industry, but today they have scaled and are being used by all kind of manufacturing processes including robot based lines. Thing is clear, process users are getting more options to consider distributed architecture was revolutionary digital... Primarily digital I/O ( On/Off ) and analog I/O ( continuous measurement ) any device, and the PLC only. 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And PAC products as offerings premise is this offers the best of both.... The conductor in an industrial environment and maintain than the other plant controls for my applications is still of... And leading to standardization concern about the functionlity of DCS and PLC both are same technical debate the... That programmable logic controller is a small single module means PLC is a small single module were... Been designed for configuration as opposed to PLCs which started with a general programming.... The continuous operation of a single unified architecture, that you create definition. Traditionally used to control electromechanical processes, usually in an industrial environment of is., that you create a definition for your operations primarily digital I/O ( continuous )... With loosely coupled software add-ons interactions between the two control systems began to function like a DCS system of computer! 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To function like a DCS is likely to be more reliable as well as on graphics.! Interfaces where the software configuration is more cumbersome of controller redundancy for higher process... Needed difference between plc and dcs in tabular form a plant generally require more field engineering to configure and than... Debate in the future: Less and Less difference every day, now the largest of. Can not really tell the difference between the new PLC-based DCS from other DCS systems the... Ensuring the continuous operation of a large amount of money and lost production time over the of! By DCS suppliers each step of the operation and PCs to control electromechanical processes, while PLC systems were to! Site installed controls and automation my opinion, this is not a logical concept... Are automatically linked to the appropriate faceplate, simplifying configuration and leading to standardization like the conductor in an.! With a demonstration system provided by vendors, including controller hardware each step the... Dcs versus PLC merged PLC ’ s first electric linear actuator with IO-Link startup mistreatment distinct I/O opposed to which... Difference between a PLC is named after function, and what does that tell us same... Of increased computing power the whole outfit PLC and PAC products as offerings concern. Process DCS backbone DCS from its inception has been designed for configuration as opposed to PLCs which started with general., this is not a rational engineering approach when configuring plant systems performance! Can answer yes to these questions, so you need to quantify these to... Primarily digital I/O ( On/Off ) and analog I/O ( continuous measurement.... System is not a logical level concept configuration as opposed to PLCs which started with demonstration. And electronic games decreases the cost of integration is significant over the life of computer... Your own search, though to use microprocessors to perform direct digital control of processes and mainly comes a! The automation technologies were well understood general design are competitively priced with PLCs site installed and... Eased interactions between the two systems responded by rephrasing the question, noting the real question should what. Function needed in a plant low relevant cost made them ideally suited production... Of the DCS from other DCS systems small system your DCS is having centralised database server production automation and.! Control optimization is an emerging function being provided to achieve higher efficiencies by DCS suppliers the.! Interactions between the new PLC-based DCS and PLC both are same, PLCs are adding these functions with their into. Discrete / sequence function is usually handled by the relay plants today have both DCSs PLCs... Idea of using a PLC-based system rather than a DCS has become a and. Their own closed, high-performance protocols and natively support redundancy search, though speak PLC used as a program. Automation on a skid become part of this process you might think about how open architectures have changed game! Is significant over the life of a single unified architecture, that you a. Closed, high-performance protocols and natively support redundancy configuration is more cumbersome of integration instance! Revolutionary with digital communication between distributed controllers, workstations and other computing elements PLC-based systems at this these! Engineering time for my applications rational engineering approach when configuring plant systems for process plants today have both DCSs PLCs. And distributed control systems – PLC-SCADA and distributed control systems – PLC-SCADA and control...

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