If we take a closer look at the architecture of SCADA it becomes clear, that it contains much more than just HMI’s.
SCADA System Architecture with several HMI’s in a network A SCADA system can have many HMI’s to control and monitor different parts of a plant. Because where the HMI is just the screen or the interface itself, SCADA is an application or a whole system behind all those screens. But now you will often have a touch screen either at the machine or in a control room.īut if all these screen are called HMI, what is SCADA exactly then? Back in the days an HMI was really just a bunch of push buttons and control lamps. They are the interface between the operator and the machine. SCADA system with PI&D for controlling and monitoringĪll these screens are essentially HMI’s or human-machine interfaces. Most important is it, that the operator understands the different parts of the SCADA system and what they control/monitor. a P&ID (piping and instrumentation diagram). More than often multiple screens where an operator can both control and monitor all relevant components in a unit, machine or even a whole plant. What a SCADA system physically will look like is a screen. Especially the latter is how you will often see SCADA systems in use. The SCADA basics is really about exchange of information and the ability to control and monitor. Like an order for example.Īgain, the SCADA system is the meeting and connection point between information and operation. Information that has to do with business and planning. But at the same time also to send and receive information from the MES or ERP system above. The job of SCADA is really to control and monitor all this OT. SCADA System in the Automation Pyramid from ISA-95 (IEC 62264-3)īelow the SCADA system is all the operational technology like PLC’s, sensors etc. Right where IT (information technology) meets OT (operational technology). SCADA systems are placed right in the middle of the automation pyramid. And at the bottom you have all the operational systems. At the top you have all the information systems for handling business, planning and logistics.
The automation pyramid is a concept published in ISA-95 and IEC 62264-3, in an attempt to describe how different systems work together. SCADA systems are located at the monitoring and supervising level in the automation pyramid. A good way to make an understanding, of what a SCADA system is and where it can be used, is to see it in relation to the automation pyramid. It is widely used in factories to monitor and control production lines and machines. It's down there with CompactBlock IO as far as pricing goes and has a very interesting mix of I/O on board.SCADA stands for Supervisory Control and Data Acquisition and is a system for monitoring and controlling and as the name implies, data acquisition. One of the least expensive is not easily found, the Bulletin 100 DeviceNet DSA (DeviceNet Starter Auxiliary, aka DNY module) which looks like it's intended to be used to retrofit a non-DeviceNet starter but it's best use seems to be as a low density DeviceNet IO card that includes DeviceLogix capability. AB has a couple drives, IO cards, and starters which have this capability.
This is the most interesting option as essentially you bury function block logic inside a drive or an IO card directly. The PLC becomes sort of a "supervisor" function while the servo drive usually runs a motion control program. These were essentially created specifically for the purpose. Especially useful for discrete manufacturing machinery. These give you millisecond or submillisecond timing based on position feedback sensors. Programmable Limit Switches (PLS's) from Gemco or AMCI. There are basically 3 methods that I've used: 1. If you want faster, then you have to go to the hardware level. This is as fast as it gets but the input (only 1) must be hardwired to the PLC. If you want truly "fast" responses at the PLC-level, look into the PII (an interrupt in the processor settings).