Initially, to control the manufacturing processes, industries used relays. The relay control panels need to be regularly replaced, consume a lot of power and it was difficult to figure out the problems related to it. To solve these issues, Programmable Logic Controller (PLC) and Supervisory Control And Data Acquisition (SCADA) were introduced.
What is PLC?
PLC (Programmable Logic Controller) is a digital computer generally used for the automation of various electro-mechanical processes in industries. These controllers are specially designed to survive in rough situations and shielded from heat, cold, dust, and moisture etc. PLC consists of a microprocessor which is programmed using the computer languages such as Ladder diagram (LD), Sequential function charts (SFCs), Function block diagram (FBD), etc.
The PLC receives information from connected sensors or input devices, processes the data, and provokes output based on pre-programmed parameters.
Depending upon the inputs and outputs, a PLC can monitor and record run-time data such as productivity of machine or operating temperature, automatically start and stop processes, trigger alarms if a machine malfunctions, and more. Programmable Logic Controllers are an adjustable and long-lasting, control solution, adaptable to almost any application.
What is SCADA?
Generally, SCADA system is classified into two parts:
- Clint layer
The Clint layer which feeds the main machine interaction.
- Data server layer
The data server layer which handles most of the process data.
SCADA (Supervisory Control And Data Acquisition) is a category of software application program for process control, the collection of data in real time from remote locations in order to control apparatus and conditions. SCADA is used in power plants as well as in oil and gas refining, telecommunications, transportation, water supply and many more.
SCADA systems include hardware and software components. The hardware collects and feeds data into a computer that has SCADA software installed. The computer then processes this data and displays it in a timely manner. SCADA also records and monitors all events into a file stored on a hard disk or sends them to a printer. SCADA applications warn when conditions become hazardous by sounding alarms.
Difference Between PLC and SCADA
|
PLC |
SCADA |
| Sub-systems are usually located within a limited factory or plant-centric area. | Geographically distributed field sites.
|
| Communications are usually performed using Local Area Network (LAN) technologies. | The communication system can be set up for a long distance |
| Usually, employ greater degrees of closed-loop control than SCADA systems.
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It is mainly designed to handle long distance communication challenges like delays and data loss generated by the various communication media used. |
