ifference between PLC,DCS & SCADAIn the past the strength and weakness of both the automation technologies were well understood. Does the system support the industrial network interfaces I need now and in the future? if DCS stopped, all system is stopped. Does the system reduce engineering time for my applications? 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 … 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”. In turn, there are DCS vendors that have introduced PLC and PAC products as offerings. When is encoder resolution specified in bits, and what does that tell us? Joined: 9/27/2006. 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. 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. 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. The controls and automation on a skid become part of the plant just as much as site installed controls and automation. Does the system support the enterprise software interfaces I need now? 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. A PLC is a digital computer used to control electromechanical processes, usually in an industrial environment. 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. As you can see, there are a lot of similarities between the two systems. Typically, their interfaced … Following this logic, the decision is between the new PLC-based DCS and traditional DCS offerings. 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. 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. Most systems can answer yes to these questions, so you need to quantify these characteristics to make solid decisions. 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. 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. PLC specialist Mart n Hilbers talks about the differences between a PLC-SCADA control system and a DCS configuration. Both DCS and PLC can be configured or reconfigured. 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. This can be accomplished with a demonstration system provided by vendors, including controller hardware. Advantage DCS. DCS versus PLC. It can be seen from the name: PLC is named after function, and DCS is named after architecture. 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