The SCADA Node communicates in real-time with automation equipment. The SCADA node is physically connected to automation hardware via Serial, Ethernet or proprietary communications. Typical automation equipment include Programmable Logic Controllers (PLCs), Single Loop Controllers, Direct Digital Control Systems (DDC), Distributed Control Systems (DCS) and IO (input / Output) systems. The SCADA node is not a web server (usually).
The SCADA Node is the computer directly connected to a plant control system. The SCADA Node typically has a serial, Ethernet or proprietary network card communicating directly with PLCs, Controllers and IO racks. The SCADA Node also has a network connection to Clients. The SCADA Node retransmits data between the controllers and clients. In a sense, the SCADA node is a "SCADA Server".
The SCADA node can be a Blind node or have its own Local Interface (called View DAQ).
There can be an unlimited number of SCADA Nodes in the system.