PLC vs SCADA vs DCS (Detailed Response)
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- เผยแพร่เมื่อ 2 ส.ค. 2020
- In this video, Walker Reynolds shares a detailed response to the differences between SCADA PLC and DCS. This is a detailed response to a question in our previous video which you can watch here: • PLC vs SCADA vs DCS
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There's a lot of videos from big channels out there trying to explain these concepts. You've done the best job in my opinion giving a very practical explanation! thanks for the videos!!!
Thank you Edgardo! Would you mind if we used your comment as a testimonial for our IIoT Mini-Course?
I have watched so many videos trying to explain the difference..yours is the best! Explaining the crux in such layman terms!! Great work!!
Glad we could help!
Best explanation I've ever seen on TH-cam
Glad to help ❤️
Great diagrams. Excellent explanations. Always learning from Walker!
Thanks for watching!
Best explanation of all the videos i have encountered. Thanks a lot.
Glad it was helpful!
I was the first person who asked this question. By the way, nice explanation as always.
thank you for asking such a great question!
best explanation ever!!!! Thank you so much for this info👍
Glad it was helpful!
Thanks 👍
No problem 👍
I really Appreciated your video, Great Guidance for who are interested career in the Industry 4.0
Glad it was helpful, Sudhir!
Not sure where you're getting your information, but you are dead wrong on several items here. IF you are talking about modern DCS's, then pretty much all of those (that I know of) communicate over a dedicated Ethernet backbone. So this "blisteringly fast" BUS you refer to is nothing more than Ethernet. Same for Allen-Bradley and Siemens PLCs for sure. And in fact, MOST PLC processors are capable of reading and computing many times faster than any DCS. Some processes require millisecond response times; that's a PLC. Typical RPI on a remote I/O device in a Rockwell system is in the sub 100 ms range. Not so on a Honeywell Experion system, DeltaV or Foxboro. The only "DCS" that I'm aware of that matches a PLC in I/O and processing speed is the GE Mark VI, and it was designed specifically to run turbine generators, which need that kind of speed. The vast, vast majority of process automation only needs I/O and processing speeds in the 1/4 second range at best. You simply don't need ms speed for flow control or VFD control, certainly not motor starters or discrete valve controls unless you intend to destroy your equipment.
Another place you are misinformed is that most of those pre-written function blocks in a DCS (and PlantPAx) are designed for very common, basic automation functions such as controlling a discrete device like a dual solenoid valve or a motor starter. Sure, there are some that have been developed for very specific equipment, but those are not the "out of the box" stuff you get when you buy a DCS. You would have to purchase those separately because a lot of development time has gone into them. A pulp mill digester scheduler is a good example, or maybe a brewing scheduler.
PlantPAx process objects are nothing more than bundles of code that make it easy to connect the appropriate I/O references, set a few parameters and tada, you have a fully functioning PID controller, just like Honeywell, Emerson, ABB, or whatever can do. But these are absolutely NOT designed for a specific device like a rolling mill. And BTW, I've worked in multiple steel mills making multiple steel products. Every single one of them used Allen-Bradley and/or Siemens PLC's! Not a DCS in sight!
In reality, PLC's and DCS's are 90% the same thing nowadays. DCS's were once all built on a proprietary software platform but are pretty much all Windows based now. And almost ALL systems utilize Ethernet as their backbone. Sure, old BUS technologies still exist but only because there are still a lot of devices that require protocols like Profibus, Modbus, RS232, DeviceNet, ASi...etc, and they all absolutely SUCK. The biggest difference between a PLC and a DCS is that the HMI is an imbedded part of the DCS and not with a PLC and the speed difference, which is faster in PLC's, not DCS's.
The other big difference is scaling and price. DCS's are too expensive for small machines, which is why EVERY small machine, skid system and OEM comes with a PLC of some kind, NOT a DCS. You simply cannot buy a DCS of any kind and put it on a machine the size of a kitchen table for under $5,000. That just doesn't exist in our world.
Sorry to dump on your video but I had to point out these errors.
Consider this a free dumping ground! Thank you for your detailed comment Mark!
Thank you for the brilliant explanation sir.
I have one doubt, Now i find PLC's are coming with distributed I/O architectures. Can you please put some light on its functional difference with DCS.
Hi Satz. Thank the difference is based on the application DCS are closed and high speed, turn-key. PLCs are like legos. Thank you!
That was a terrible answer from Walker. PLC's are nothing like "Legos" and anyone who's ever worked with them knows this. In fact, you can buy scores of Lego sets that are designed to build only one thing, like an X-Wing. So I have no idea what he's even talking about. It's like he's saying a DCS comes pre-built to run your plant. Nothing could be farther from the truth. I've configured dozens of systems and have yet to see one out of the box ready to anything but light up.
When you purchase a brand new DeltaV system (for example), what do you get? You get a blank controller, blank HMI, blank stations and some I/O cards, same as any PLC. You have to build EVERYTHING yourself. Both PLC's and DCS's come with basic control blocks that you can configure to suit your needs. Both come with distributed I/O architecture. Both communicate across an Ethernet backbone. Both come with single or redundant processors and I/O structures, ring, star and linear architectures. Both offer Basic Process Control System (BPCS) and Safety Integrated System (SIS) versions. Both offer various SIL protection levels. Price and scalability are the most important features in determining which is best for your process.
What is the difference between MES and SCADA?
MES is for ordering and maintaining parts. SCADA is for observing/interacting with process data.
I search so many videos to find the answer. Only this video I can understand.
Thank you!
Best explanation ever!!
Glad you think so!
Walker, you’re great, I hope you see this. In this case I think there is a large misconception. DCS is NOT for high speed. AB PLCs are much better for high speed applications. What is faster with DCS is deployment since so much is prebuilt. DeltaV for example CANNOT handle fast things. Think of it this way- DCS grew up in the process world where things like temperature and pressure are of concern. These variables change over seconds or minutes. PLC is great for high speed printing, DCS cannot even do it the hardware can’t even handle processing that fast.
Glad to see others catch this mistake. I would like to see Walker amend his video so these misconceptions are not propagated. I've had to explain this to numerous young guys just entering the automation field and dispel the myth that one is better than the other when in fact they have each served different needs in industry for ages.
I would say that regarding deployment, DCS's have few real advantages there. Because most PLC manufacturers have incorporated functional control blocks for basic devices like valves, drives and motors, this advantage has vanished. However, some manual configuration is required to establish communications between PLC processors and that is a real advantage for a DCS, which is literally just a few clicks away from getting a bunch of controllers to communicate any of their data with one another. Not so with a PLC. This is something the PLC guys need to work on.
Thank you for clarifying Derrek.
acronym usage is killing science and technology, why not use context to lend understanding instead of dummy notes for everything which is content specific and realm specific, a person will encounter unnecessary road blocks when attempting to traverse through engineering platforms due to localized acronyms used only by people within the field. most of your videos and people like you are spent explaining how ideas fit into letter oriented boxes instead of the idea in which
your profession was designed to propagate. offering no real actionable intelligence just useless jargon, this is why russian engineering always wins the day, no matter what we do in the west we convolute it to a point of uselessness,
get to the point and let dummies catch up 🤷♂️