Automation and IIoT
What is SCADA (supervisory control and data acquisition)?
SCADA supervises and controls industrial processes through PLCs, HMIs, alarms and historians. How SCADA works, where it sits in ISA 95 and how it differs from MES.
Quick answer
SCADA (supervisory control and data acquisition) is the software and hardware that lets operators monitor and control industrial processes from a central point. It gathers data from PLCs and remote terminal units, shows it on HMI screens, raises alarms, stores history and sends setpoints and commands back to the equipment.
Updated 30 October 2026. Written by the Ajinkya Technologies engineering team, reviewed by Amey Kadle.
SCADA explained
A SCADA system has four main parts: field controllers (PLCs and remote terminal units) that run the actual control logic; a communication network using industrial protocols; servers that collect data, manage alarms and store history in a historian; and HMI clients where operators watch and act. In ISA 95 terms it sits at level 2, supervising the control layer below it.
SCADA is about the process in real time: is the pump running, is the tank level in range, which alarm needs attention now. It is not designed to manage production orders, materials, quality records or labour. That is the job of an MES at level 3, which takes production orders from the ERP and tracks what was made, with what, by whom and how well. In many plants SCADA and MES exchange data continuously: SCADA provides counts, states and process values; MES provides orders, recipes and context.
Because SCADA can change physical equipment, its security matters more than most IT systems. Guidance such as NIST SP 800-82 and the ISA/IEC 62443 series recommends segmenting OT networks into zones, controlling every connection between them, and treating remote access with particular care.
Key concepts
- Field controllers, network, servers, HMI clients
- Alarms, trends and a historian
- ISA 95 level 2, supervising control
- Process focus, not orders or materials
- OT security: zones and controlled conduits
Questions
What is the difference between SCADA and MES?
SCADA supervises the process in real time: states, values and alarms. MES manages production execution: orders, materials, quality, labour and performance, and links the shop floor to ERP.
What is the difference between SCADA and a PLC?
A PLC runs control logic for a machine or process. SCADA supervises many PLCs, shows their data on screens, handles alarms and stores history.
Is SCADA the same as DCS?
They overlap. A DCS (distributed control system) is an integrated control system common in continuous process plants; SCADA is typically used for supervising PLC based or geographically spread systems.
References
How we help with SCADA
We integrate SCADA systems with MES and ERP, read their data through OPC UA, MQTT or Modbus without changing control logic, and build HMI and SCADA screens for system integrators.
Interactive 3D demo with simulated data: cut the network and watch the edge store and replay.
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