Difference between RTU & PLC and also SCADA VS HMI
- Thread starter ivanlch
- Start date
BASIC ELECTRICAL TEC
Member
An RTU would be a dedicated type of controller that will be designed for a very specific function, and not 're-programmable' for other uses. IE a pump controller monitoring output pressure and reservoir level, where there may be two analog inputs (pressure and level), one analog output (pump speed reference), 4 discrete inputs (local/remote switch and failsaife inputs), 4 discrete outputs (start pump, local indicators).
'SCADA = System Control And Data Acquisition' is more of a broad description of what a system will be required to do. And an HMI (simple as a selector switch panel, complex as a multi-page touchscreen display) would be one part of a SCADA which is controlling, monitoring, accepting operator inputs, collecting system data, storing data in a historian.
And SCADA usually refers to a larger, plat-wide or area-wide, system possibly comprising several PLC's and HMI.
'SCADA = System Control And Data Acquisition' is more of a broad description of what a system will be required to do. And an HMI (simple as a selector switch panel, complex as a multi-page touchscreen display) would be one part of a SCADA which is controlling, monitoring, accepting operator inputs, collecting system data, storing data in a historian.
And SCADA usually refers to a larger, plat-wide or area-wide, system possibly comprising several PLC's and HMI.
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A book that I read states that SCADA consist of a HMI, PLC and RTU.
Can SCADA exist if a system only consist of HMI and PLC? Can PLC act like RTU?
RTU is Remote Terminal Unit - this can be stand alone or remote I/O off a PLC.
HMI is Human Machine Interface - this can be SCADA or colour touch screen or mouse or keyboard - other things too of course.
HMI and SCADA can be the same thing as above.
PAC is just a more powerful PLC - many of the newer PLCs fit into the PAC marketing hype rubbish.
By the way, Citect has a 'disk PLC' for manipulating data - not sure about other SCADA packages.
HMI is Human Machine Interface - this can be SCADA or colour touch screen or mouse or keyboard - other things too of course.
HMI and SCADA can be the same thing as above.
PAC is just a more powerful PLC - many of the newer PLCs fit into the PAC marketing hype rubbish.
By the way, Citect has a 'disk PLC' for manipulating data - not sure about other SCADA packages.
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System Control and Data Aquisition (scada) can be done, to a limited extent, on a HMI screen.
but, A HMI does not have the storage capacity of a PC or Server.
So Scada is popular for that purpose.
As you Progress,in the automation industry, the equipment you need is dependant on what system the customer wants or needs
but, A HMI does not have the storage capacity of a PC or Server.
So Scada is popular for that purpose.
As you Progress,in the automation industry, the equipment you need is dependant on what system the customer wants or needs
BASIC ELECTRICAL TEC
Member
Ahh yes, I apologize, and concur.
What's in a name? Every bus, car, van or truck is in essence an automobile, it's mobile and it is doing it on itself, without being pulled or pushed. But not every automobile is a bus, or a truck or a van or a car. A lot depends on the person using the word...
Kind regards,
Kind regards,
micky
Lifetime Supporting Member
Pretty much sums it up.
PeterW
Member
Not quite true, the RTU's I see are used in the oil and gas industry and are programmable (SCADAPack for example). These are made for distributed control, ie pumping stations distributed across a wide area. These are like 'brick' style PLC's with I/O included and would have built in calculation software for oil and gas flow rates etc. Also include ports for radio communications.
I've noticed since coming across to Canada from the UK that the Canadian engineers refer to HMI's all the time, whether they mean HMI's or SCADA. Whereas in the UK, a HMI was usually a small purpose built operator interface, like panel mate, OP70's etc and SCADA is usually a PC system with capabilities of a large database etc, like InTouch and WinCC.
originally HMI refered to a screen type control, touch or keypad.
Now it means everything.
- a panel full of buttons and lights is a 'Human Machine Interface'
So now you need to ask the customer "What do You want?"
often they dont know.
Now it means everything.
- a panel full of buttons and lights is a 'Human Machine Interface'
So now you need to ask the customer "What do You want?"
often they dont know.
Terminology gets confusing because it doesn't adhere to any hard and fast rules. I had a helluva time explaining to the plant manager the difference between PLC programming software, and the PLC program. Technically they are both "programs" but we don't refer to them that way. You just have to take things in the context in which they are used.
saultgeorge
Lifetime Supporting Member
ivanlch I worked for a large water utility out west. We of course had a SCADA system at the main campus and at the lake treatment plant. Every site, whether a well, pumping station or a reclaimed water pumping station, had an RTU and a PLC. We called them a Remote Telemetry Unit. They had a processor that interfaced with the radio signal from SCADA and then passed commands to small relays that gave inputs to the PLC. Any data that you could get from the PLC (Analog, Digital status, etc.) would be transmitted back to SCADA. We had a whole shop (department) called Telemetry who built and maintained these units plus a couple of SCADA programmers and a couple of radio guys. That's how I see the differences.
harryting
Lifetime Supporting Member
2013, yall.
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