In the realm of industrial automation, understanding the distinctions between various terms is crucial for optimizing operations. Terms like SCADA (Supervisory Control and Data Acquisition) and HMI (Human-Machine Interface) are often used interchangeably, yet they serve different purposes within the automation ecosystem. This blog focuses on SCADA as a widely distributed system across facilities and remote sites, while HMI is the visualization component of SCADA. Additionally, we will explore how modern SCADA systems employ organizational concepts from ISA-101 High Performance HMI to enhance functionality and user experience.

What Are SCADA and HMI?

This guide breaks down the differences between SCADA and HMI, highlighting how each uniquely contributes to improving operational efficiencies and decision-making processes in industrial settings.

Supervisory Control and Data Acquisition (SCADA)

SCADA is a comprehensive control system that oversees and manages various operations across a facility or multiple remote sites. Acting as the nerve center of industrial processes, SCADA systems gather real-time data from numerous sources, analyze it, and provide operators with a detailed overview. This high-level perspective allows for swift, informed decision-making, ensuring optimal performance and efficiency across the board. 

Human-Machine Interface (HMI)

HMI, on the other hand, serves as the graphical visualization component within a SCADA system. It allows operators to interact with the machinery and processes by providing a graphical representation of the industrial process. HMIs enable operators to monitor equipment, view data trends, and make necessary adjustments seamlessly. Essentially, HMI is the bridge between operators and the complex machinery they oversee, facilitating smooth communication and control. The levels of HMI organization, as outlined in ISA-101, ensure that the interfaces are designed for optimal performance and usability.

The Differences Between SCADA and HMI

While SCADA and HMI are integral to industrial automation, they serve distinct purposes. Let’s explore the key differences between SCADA vs. HMI.

Scope and Functionality

SCADA systems have a broad scope, overseeing entire industrial processes potentially across multiple sites or large geographic regions. They manage large volumes of real-time data from various sensors and devices, providing a comprehensive view of operations. In contrast, HMIs focus on specific tasks within a process or machine, offering a graphical interface for operators to monitor and control individual components or subsystems. HMIs are often seen as industrial panel-mounted touch screen displays, or in modern systems can be thin clients. HMI terminals can also be found in control rooms and operations centers.

Level of Control

SCADA systems offer supervisory control capabilities, allowing operators to manage entire processes and make high-level decisions based on aggregated data. They can initiate control actions, set alarms, and optimize process parameters to improve efficiency. HMIs, however, provide local control functions, enabling operators to interact directly with specific equipment or machines, adjust settings, and respond to immediate operational needs.

Complexity and Scalability

SCADA systems are designed to handle complex, distributed processes with extensive networking capabilities, supporting large-scale operations. They are highly scalable, capable of managing thousands of data points, and can integrate with enterprise-level systems. HMIs, being simpler and more focused, cater to the specific requirements of individual machines or processes. While they may lack SCADA’s scalability, they offer flexibility and ease of use for localized control tasks. 

The Role of ISA-101 in Defining SCADA and HMI

ISA-101 plays a crucial role in clarifying the distinction between SCADA and HMI by providing a structured approach to HMI design. In ISA-101, the “Operator Sphere of Influence” refers to the range of information and control an operator needs to perform their duties effectively. This concept emphasizes providing operators with access to relevant data and control capabilities that directly impact their responsibilities, without overwhelming them with extraneous information. The sphere of influence is structured across the hierarchical levels of HMI organization:

• Level 1: Process Overview – Operators can quickly scan the entire system’s status, identify major issues, and ascertain overall performance, providing a macroscopic view of the operations.
• Level 2: Area Overview – Focuses on specific sections or units of the process, allowing operators to monitor and make decisions about particular areas within their control.
• Level 3: Detailed Process Control – Offers detailed control and real-time data for specific equipment or process parts, enabling operators to interact with and manage individual components.
• Level 4: Maintenance, Diagnostics, and Configuration – Provides in-depth information for diagnostics and maintenance tasks, typically used by specialized personnel for troubleshooting and configuring system parameters.

For a deeper understanding of how ISA-101 enhances HMI designs and supports the distributed nature of SCADA systems, read our blog post Unpacking ISA-101: Beyond the Misunderstood Grayscale.

Integration With PLCs and RTUs

Both SCADA and HMI control systems interface with programmable logic controllers (PLCs) and remote terminal units (RTUs) to monitor and control industrial processes. SCADA systems typically serve as the supervisory layer, communicating with PLCs and RTUs to gather data and issue commands across distributed systems. 

HMIs are often used for local control tasks, interfacing directly with PLCs to provide operators with real-time feedback and control capabilities at the machine level.

How Do SCADA, HMI, and PLC Work Together?

SCADA and HMI work in tandem to enable efficient industrial automation processes. SCADA systems, with their supervisory capabilities, gather real-time data from various sensors and devices across the industrial environment. HMIs then process and display this data, providing a user-friendly interface for operators to monitor and control the systems. Together, they create a cohesive ecosystem where operators can access both macro- and micro-level insights.

In this relationship, PLCs play a crucial role in handling the control logic and decision-making processes within the system. They receive commands from the SCADA/HMI software and execute them by controlling actuators, motors, valves, and other devices. SCADA, HMI, and PLCs form a symbiotic relationship where SCADA gathers and processes data, HMIs provide intuitive interfaces, and PLCs execute control commands.

The Role of RTUs in SCADA/HMI Software

RTUs act as intermediaries between field devices and the central control system. They collect data from sensors, meters, and other equipment in remote locations and transmit it to the SCADA/HMI software for analysis and monitoring. RTUs also receive commands from the central system and execute control actions in the field, such as adjusting valve positions or activating pumps. This ensures real-time data acquisition and control, enabling operators to make informed decisions and optimize industrial processes efficiently.

Applications of HMI and SCADA

SCADA and HMI systems are versatile and extend across various industries, including healthcare, food and beverage, and consumer packaged goods.

Health Care

SCADA/HMI software monitors and controls parameters like temperature, humidity, pressure, and ventilation in hospital environments, ensuring optimal patient care and safety conditions. They also oversee medical equipment performance, detect faults, and trigger alerts in case of malfunctions, facilitating data logging, trend analysis, and reporting for informed decision-making.

Discover how Malisko’s comprehensive automation solutions transformed a health care optics manufacturer’s critical processes to meet regulatory compliance within record time. 

Read the full case study now!

Food and Beverage

SCADA/HMI software ensures consistent product quality, maximizes production efficiency, and maintains stringent safety standards. SCADA systems monitor and control production processes from raw material handling to final packaging, while HMI interfaces provide visual representations of the process, helping maintain optimal conditions.

Read a case study on how Malisko transformed a leading dairy producer’s separator process, enhancing yield and consistency.

Consumer Packaged Goods

SCADA/HMI software optimizes production processes, ensures product quality, and efficiently meets consumer demand. SCADA systems monitor and control various manufacturing aspects, and HMI interfaces provide operators with intuitive visualizations to monitor performance and quickly make necessary adjustments.

Read our detailed case study to discover how Malisko helped a leading laundry product manufacturer boost productivity and efficiency.

Benefits of Implementing SCADA/HMI Systems

Implementing SCADA/HMI systems offers several advantages:

1. Enhanced operational visibility with real-time data visualization.
2. Increased efficiency through automation and better data management.
3. Improved safety with continuous monitoring and alarms.
4. Advanced data analytics for trend forecasting, diagnostics, and process optimization.
5. Remote control and monitoring capabilities for faster issue responses.
6. Scalability to meet changing operational needs.
7. Cost reduction through optimized resource usage and reduced manual interventions.

Partner With Malisko to Maximize Efficiency

Leveraging SCADA/HMI systems’ collaborative capabilities can provide numerous benefits. However, deploying and maintaining these systems requires specialized expertise. At Malisko, we specialize in providing high-quality HMI/SCADA consulting services tailored to meet your unique automation needs. Let us help your business streamline productivity and improve efficiency with our expertise in modernizing plant floor controls and implementing process automation systems.

Contact us online today to start a conversation about what we can do for you.