also DCS comes with it's SCADA always. The automotive industry is still one of the largest users of PLCs. 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. Accomplishing this with PLC-based systems at this time can be approximated with loosely coupled software add-ons. Logic means the discrete / sequence function is usually handled by the relay. of I/O with less cost. 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. Most systems can answer yes to these questions, so you need to quantify these characteristics to make solid decisions. A DCS is likely to be more reliable as well, ensuring the continuous operation of a process or system. The time and cost of integration is significant over the life of a system and should be examined as part of the analysis. The first name on the team sheet, your DCS is dependable, hardworking and controls the whole outfit. 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. The material on this site may not be reproduced, distributed, transmitted, cached or otherwise used, except with the prior written permission of WTWH Media. 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. of I/O, then PLC is better from cost view. A DCS or distributed control system is similar to a PLC in that it has rugged computer controllers however the DCS contains multiple autonomous controllers that are distributed throughout a system, also used for automating processes. Programmable Logic Controller (PLC) also known as Industrial Computer is the major component in the industrial automation sector. PLC specialist Mart n Hilbers talks about the differences between a PLC-SCADA control system and a DCS configuration. 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. LINAK launches the world’s first electric linear actuator with IO-Link. Today with open technologies, DCS systems are competitively priced with PLCs. 1. DCS versus PLC. If the vendor tells you this can only be done by taking a training course on their product, don’t walk…run away from this supplier. Using same data base server you can edit in logic as well as on graphics screen. DCS is mainly used as a control system and will feature different processes which can be made up of merged PLC’s. Difference Between PLC & DCS Difference between PLC & DCS :- To perform advanced regulative management on a plant-wide scale, DCSs contain the integral infrastructure. This feature we can not achieved in PLC. The big advantage was that programmable logic controllers could be reconfigured with software programming rather than rewiring control panels. 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. 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. 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. if DCS stopped, all system is stopped. The everyday use of our smart phones, iPads, and electronic games decreases the cost of increased computing power. The PLC control and DCS control system is not a logical level concept. The DCS from its inception has been designed for configuration as opposed to PLCs which started with a general programming model. The difference between distributed control systems (DCSs) and programmable logic controllers (PLCs) can be boiled down to a simple football metaphor. 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 Either way, you go, hopefully, this article has shed some light on both the similarities and differences between … As part of this process you might think about how open architectures have changed the game. 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. DCS configuration uses standard control objects that are automatically linked to the appropriate faceplate, simplifying configuration and leading to standardization. One thing is clear, process users are getting more options to consider. Computer-based process control systems before the TDC 2000 were mainly data collection and alarm systems with controlled done by pneumatic loop controllers and standalone electronic PID controllers. But as far as concern about the functionlity of DCs and PLC both are same. When is encoder resolution specified in bits, and what does that tell us? The main difference between Programmable Logic Controller (PLC) and Distributed Control System (DCS) are: The number of I/O in the system. 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. In a nutshell, a PLC or programmable logic controller is a ruggedized computer used for automating processes. Protocols, like OPC, have eased interactions between the two control systems. It was the first system to use microprocessors to perform direct digital control of processes as an integrated part of the system. If you produce chemicals, you speak DCS. Last visit: 1/7/2021. Does the system reduce engineering time for my applications? The need to connect to multiple industrial networks is a necessity and virtually all process plants utilize multiple discrete and process industrial networks including DeviceNet, Profibus, PROFINET, EtherNet/IP, Modbus TCP, HART, and Foundation Fieldbus. 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. Ideally the plant process control system has efficient and cost effective multiprotocol interfaces for all PLC protocols. Advantage SCADA. A PLC is a digital computer used to control electromechanical processes, usually in an industrial environment. Superior speed makes PLCs a much better alternative for applications involving quick production startup mistreatment distinct I/O. DCS is dealing with very large no. ... 3 Comments on “ The Difference Between PLCs and Computers ” Richard says: January 28, … 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. 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. Many process control systems require redundancy for I/O, controllers, networks, and HMI servers at various levels. Joined: 9/27/2006. The majority of process plants today have both DCSs and PLCs installed for controls. DCSs were traditionally used to control large processes, while PLC systems were used to control machines. Of course, the difference in performance between … PLC is mainly used as a controller of processes and mainly comes as a standalone program. 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. At the same time, the DCS hybridized to incorporate PLCs and PCs to control certain functions and to provide reporting services. 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. As you can see, there are a lot of similarities between the two systems. This can be accomplished with a demonstration system provided by vendors, including controller hardware. Following this logic, the decision is between the new PLC-based DCS and traditional DCS offerings. Posts: 10313. Many agree that the beginning of the DCS started with the introduction of the Honeywell TDC 2000 in 1975. The idea of using a PLC-based system rather than a DCS has become a philosophical and technical debate in the industry. It sure looks like the PLC vendors who advocate a single control architecture for process plants are essentially creating a DCS system built around their hardware and software components. These days, there is probably no single factory in the word that d… He responded by rephrasing the question, noting the real question should be what distinguishes their PLC-based DCS from other DCS systems. If you manufacture plastic widgets, you speak PLC. 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. DCS and PLC have been pillar for control of process plant for quite some time now with advancement in technology. are connected to controllers, which are connected to the process DCS backbone. Advantage DCS. The best way to think about DCS and PLC is like this: in the majority of cases, a PLC controls a machine and a DCS controls a plant. Distributed Control Systems (DCS) have been the primary solution for process automation but now many PLC vendors are pursuing these applications arguing that a single integrated architecture based on PLCs and/or PACs (Programmable Automation Controllers) is the best approach to total plant automation. PLC-based control systems began to function like a mini-DCS. Both DCS and PLC can be configured or reconfigured. 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. The level of controller redundancy for higher level process applications is new to PLC suppliers and they continue to add options for redundancy. 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 … 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. DCS is a relatively large system while the PLC is a small system. 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. This distinction between the DCS and SIS, led to separate markets for both types of systems with separate suppliers for both, initially. 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. 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. There are plants where PLCs or DCSs control all of the plant functions but at this point these are the exceptions. PLCs on skid mounted and packaged systems for process plants are creating control and automation problems. Difference Between PLC & DCS Cont…  Generally, PLCs are stand alone and perform a particular task, where a DCS is a network of PLCs that communicate in some … Does the system support the enterprise software interfaces I need now? In principle, PLC can form DCS. 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 system realizes the function and coordination of any device, and the PLC device only realizes the functions of … DCS backbone networks are typically standard Ethernet hardware but use their own closed,high-performance protocols and natively support redundancy. In turn, there are DCS vendors that have introduced PLC and PAC products as offerings. Typically, their interfaced … It means PLC is a sub system of a large system called DCS. Concerned about safety? PLCs were originally designed to replace relay control systems and their low relevant cost made them ideally suited for production automation and machinery. In my opinion, this is not a rational engineering approach when configuring plant systems for performance and reliability. (SAP, Oracle, etc.). For instance, PLCs are faster and can handle more complex control. Your DCS is your captain. 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. This is driven by increased unit volume production of processors and related components. 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 suppliers have been developing new configuration software to provide this level of integration. A Programmable logic controller(PLC) is simply a special purpose computing device designed for use in industrial control systems and other systems where the reliability of the system is high. Currently there are two main stream types of control systems – PLC-SCADA and Distributed Control Systems (DCS). Slower processes usually need coordination across varied production units. DCS, or Data Control System, is process oriented, as it focuses more on the processes in each step of the operation. Does the system support interfaces to my legacy systems. PLCs are adding these functions with their push into process control. 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. 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”. To sum up this post, the difference between the PLC and SCADA is as follows. This distributed architecture was revolutionary with digital communication between distributed controllers, workstations and other computing elements. WTWH Media LLC and its licensors. The premise is this offers the best of both worlds. The most significant difference between the two is their general design. These interfaced subsystems generally require more field engineering to configure and maintain than the other plant controls. Rating: (2169) Hello Viana; I would say: Less and less difference every day, now. Real-time software modeling and control optimization is an emerging function being provided to achieve higher efficiencies by DCS suppliers. 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. 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. All rights reserved. Consider that mobile phone shipments in 2010 were 1.39 billion, up 18.5% from the 1.17 billion units shipped in 2009. This included primarily digital I/O (On/Off) and analog I/O (continuous measurement). At the time they were introduced (in the late '70s, and 1980s) DCS (Distributed Control Systems) were developped for continuous or batch process control of large processes: rafineries, steel mills, and such. You might want to try your own search, though. Integration with the enterprise is becoming very important to improve operations and maximize asset management. Well, I think DCS - Distributed Control Systems - is a control device that has higher capabilities compared to an ordinary PLC. 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. "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. ... PLCs may also take the form of a computer or a small single module. Need an open communication architecture? if the system has less No. In DCS systems, the process networks (Foundation Fieldbus, HART) and PLC-oriented networks (DeviceNet, Profibus, Modbus, etc.) In this article the term PLC will include PAC. It can be seen from the name: PLC is named after function, and DCS is named after architecture. DCS is mainly used to handle anolog IO's and PLC's for digitaly . SCADA is a system that relies on computers, software and communication media to remotely monitor and control devices in a control system, usually large-scale. C'mon over to where you can learn PLC programming faster and easier than you ever thought possible! 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. 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. Major worthy advantage of DCS is having centralised database server. The controls and automation on a skid become part of the plant just as much as site installed controls and automation. These PLC vendors are continually demonstrating how their software is like a DCS. Now a days you cannot really tell the difference between a PLC or a DCS. What is a PLC? 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. I suggest, rather than accepting a suppliers definition of a single unified architecture, that you create a definition for your operations. ifference between PLC,DCS & SCADAIn the past the strength and weakness of both the automation technologies were well understood. 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.) These other protocol interfaces are typically accomplished with third party interfaces where the software configuration is more cumbersome. The DCS supervises the entire process, much like the conductor in an orchestra. 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. Check out our free e-newsletters to read more great articles.. ©2020, a subsidiary of ISA, A subsidiary of the International Society of Automation. Does the system reduce process control configuration time? Although PLCs have become more powerful, they are still based on “loose” component architectures allowing functions to be easily added with hardware and software. Does the system support the industrial network interfaces I need now and in the future? 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 … This investment upfront can save a large amount of money and lost production time over the life of a system. The DCSs generally control and manage the core processes (food, pharmaceutical, refining, etc.). 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.