By Guest Blogger Andrew Green
SCADA systems are easily classified as one of the greatest data acquisition methods to have ever been invented. The ability to gather data from various distances, translate to a user-friendly format, and combine the points into a viable action plan is extraordinary. Ultimately, SCADA enables anyone to measure process performance and adjust as necessary based on those measurements.
Unfortunately, the term is enough to instill fear into anyone who does not feel intimately familiar with its role in the process. There is also a common misconception that "SCADA" refers to anything electrical or controls related. In reality, SCADA systems can be fairly complex with thousands of data points or as simple as a single remote terminal unit (RTU) pulling data and feeding it back to a computer. In a typical SCADA system, there are a few common components of which to be aware.
- Field Instrumentation: The field instruments need to be calibrated and verified on a regular basis. Most organizations and municipalities require these to be completed on an annual basis. A field instrument can be a sensor, flowmeter, or anything else that monitors the process.
- RTU/PLC: An RTU and programmable logic controller (PLC) can be one in the same or separate components. The RTU collects data from the field instrument and feeds it back (either wirelessly or through hard-wires) to the central SCADA computer. The PLC is what actually controls the field instruments. For example, a flowmeter measures higher than normal flow. The RTU sends the data (through the SCADA system) to the PLC which automatically turns off the pump or changes its speed.
- HMI: HMI stands for "human machine interface". These typically take the form of a touchscreen on a control panel or several screens on a computer. The HMI exists to take the data that has been collected and make it into a legible and understandable picture. HMIs can control PLCs, view data from RTUs, and send the data to other devices like tablets or smartphones.
- SCADA Computer: Walk into an industrial facility and find the "control room". All of the screens are showing the data fed through the SCADA computer. The computer is the actual processor of the data. Some RTUs and PLCs have processors built right in to interface with the HMI. But for instances where the data needs to be viewed from an area removed from the process, another computer is made part of the system to make the data viewable to operators, managers, etc. Once the picture is painted, the users know what actions to take as a result of the data.
"SCADA" should not be a term that confuses, but comforts. The data is gathered, processed, and acted upon. The SCADA system tells users when there is an issue with the process and gives visibility to key performance indicators. The ability to take the data and act accordingly is not just the value proposition of the system, it's what makes SCADA such a great addition to countless processes throughout the world.
Great input except for one missing item, clarification of the term SCADA . Nowhere in the blog is it defined (Supervisory Control And Data Acquisition). Such terms should always be defined at least once in the text.
David--Thanks for catching that important omission. We'll do better with future posts on this subject.