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What is HMI? Understanding Human Machine Interface (HMI)

When you are new to the world of industrial control, you hear a lot of confusing and complex concepts, one of which is Human Machine Interface or HMI. This post will clarify the concepts and fundamentals of industrial HMIs.

Let’s dive right in and understand what HMI is.

HMI+PLC System

Table of Contents

HMI Definition

In an industrial environment, a Human Machine Interface (HMI) is a means for the operator to interact with a machine, process, or system and control it from a central screen. Controlling a system from a central display can be found in almost every automatic system like car control, washing machine, airplanes, and many more.

The term HMI is mainly used, but you can find different terms like:

  • GUI – Graphical User Interface
  • MMI – Man-Machine Interface
  • LOI – Local Operator Interface
  • OT – Operator Terminal
  • OIT – Operator Interface Terminal
  • SCADA – Many people are confused about the difference between HMI and SCADA;

In this blog post, we will clarify the difference.


Operators, managers, and control engineers on the factory floor use HMIs to display complex process data as valuable and simple information.

The HMIs helps the staff monitor machinery to ensure it’s working correctly and is easy to understand. Visual displays give meaning and context to data ranging from tank levels, pressure and vibration sensors, motor, and valve information, and much more.

Advanced HMIs enable managers and engineers to do much more than control processes. Using historical and trending data, they can improve product quality and make systems more efficient and robust.

Not all HMIs are created the same; HMI solutions can come in various forms, from standalone terminals to advanced touchscreens, multitouch-enabled control panels, push buttons, computers with keyboards, mobile devices, or a tablet. A factory may have one central SCADA or numerous distributed HMIs connected through the network.

HMI History

The evolution of HMIs is parallel to the computer advancement that started in the 1960s and was called command-line interfaces. There was a significant need to interact more efficiently with the production machines in the industrial environment. Therefore, an electrical HMI was used, also known as the electric synoptic panels.

Lamps indicate changes in the process and push buttons to activate the equipment.

Those panels take a lot of effort to build and more to make changes once they are ready. It also includes a lot of unnecessary complexity in the maintenance of the system.

Synoptic Panel

In the 1990s, Microsoft introduced the Windows operating system, and then HMI design began to integrate graphical displays so that you could change the design of a graphic part with a few clicks of a button.

Uses of HMI – Features and Benefits

Usually, HMIs communicate with a PLC (Programmable Logic Controller) and field sensors to receive and display information for the operator. HMI screens can be very simple, from single function (monitoring) to more complex operations, like managing batch operations and changing production speed or recipe.

HMIs aim to optimize the process by leveraging the information displayed in graphs, charts, dashboards, and alarms.

Some of the uses of HMIs on the plant floor are highlighted below:

  • Visualization – A high-performance HMI can give enhanced visibility into the process. It enables monitoring the system performance from a single dashboard (which can also be done remotely). These capabilities help to improve productivity by responding to alerts more quickly.
  • Control – push buttons on the screen enable the operator to control the system, activate pumps, start the process, or manually open a valve.
  • Communicate with the field controllers and sensors.
  • Communication with higher systems like ERP, SCADA, and MES systems.
  • Track data history, trends, KPIs, and production time.
  • Monitor Alarms – Alarms are an important use of the HMI. The operator can be informed of a problem and directed to the location of the issue.

HMIs provide several benefits to the operators in the factory, including:

  • Efficiency: HMI provides insight into real-time data and can be used to monitor production, which can be adjusted on demand. Visualization can dramatically help identify spots where you can improve the efficiency of your operations, especially when combined with data analytics.
  • Improved downtime: With alerts on a central dashboard, you can quickly respond to or recognize a problem before it affects the system.
  • Improved usability: HMIs displays and data visualization can be developed to make it easier for the users to interact with the system.
  • Unified system: You can control all equipment from the same platform, making it easier for operators to learn how to control equipment. You can also view all your data in one location, helping you get a clear overview of your entire facility. Additionally, all users get real-time updates, so your team is always on the same page.
  • Enhanced Security: An intuitive HMI control means fewer errors. Control commands can be enabled only for supervisors to increase security and quality.
  • Robustness: A robust HMI requires no moving parts in harsh conditions. Industrial HMIs can withstand those conditions better than keyboards, mouses, and computers. This way, the equipment will work more reliably and last longer.
  • Flexible: With an HMI display, process changes do not require rewiring a control panel. Instead, users can update the software. HMI developers can also easily create custom dashboards based on their needs and preferences to increase efficiency.

HMIs come in various forms, from built-in screens on machines, to computer monitors, to tablets. Regardless of their form, the purpose is to provide insight into system performance and progress.

The complexity of the HMI application varies according to the complexity of the controlled system. It also varies according to how the HMI is developed, if the developer follows the recommended HMI developing guidelines (like color codes etc.), or his preferences.

Users of HMI

The most common job roles using HMIs daily are:

  • Supervisors – Directly supervise and coordinate production activities on the factory floor and its workers, such as operators, also in charge of a higher level of security regarding the HMI operation.
  • Control engineers (control system engineers) – Developing the HMI application according to the definition of the supervisors. Also, make changes to the application whenever needed.
  • Operators – operators are the end-users of the HMI. They are responsible for the machine/process/system. They must monitor the HMI data, diagnose problems, and make decisions accordingly.

Operators, managers, and supervisors on the factory floor rely on HMIs to provide useful information about the factory process.


The HMI’s setting, displays, and alarms are developed by a control engineer with the help of brand and model-specific software provided by the HMI manufacturer.

HMIs are used in every industrial factory, plant, and organization to interact with their machines and optimize their industrial processes.

Industries using HMI include:

  • Food and beverage
  • Energy
  • Automotive
  • Manufacturing
  • Pharmaceuticals
  • Oil and gas
  • Power
  • Recycling
  • Transportation
  • Water 
  • Wastewater
  • building


SCADA and HMI are related and sometimes referred to in the same context since they are both parts of a more comprehensive industrial control system. Nevertheless, they offer different features and intentions. While HMIs primarily focus on retrieving information and visual presentations of local systems/processes, SCADA (Supervisory Control and Data Acquisition), on the other hand, has more significant data collection and control of several sub-systems like an entire production line or factory.

SCADA System

HMI’s historical data collection and record or the ability to connect to databases are minimal. On the contrary, SCADA systems are designed especially for those purposes.

HMI and SCADA are confused because of their similarities and the fact that they work together. An HMI can be part of a SCADA system or standalone system.

The SCADA system is a factory or plant’s central overall control system that regulates all the complex operations, while the HMI is one of its components.

You can get more information in the post The difference between HMI and SCADA.

HMI Design Fundamentals for High-Performance

Control engineers who design and implement the HMI application and the operators who are the end-users of the HMI are more demanding of a high-performance HMI.

High-performance HMI is a method of HMI design fundamentals that helps ensure fast, compelling interaction. By only drawing attention to the interface’s most necessary or critical indicators, this design technique allows the operators to see and respond to problems quickly and efficiently. High-performance HMI is simple, clean, and purposely cleared of many graphics and unnecessary drawings that can confuse or take attention from alarms or essential indicators.

Features like color, size, and placement are designed by the guidelines set for high-performance HMI to optimize the user experience.

Todays and future HMI

Today’s HMIs are very advanced; besides the visualization and the alarms, they also support database connection and historical data collecting capabilities. And even more advanced features like email/SMS alerts and remote monitoring.

The industrial protocols supported by almost every HMI manufacturer are very diverse and stable.

New trends in HMI:

  • High-performance development – HMI application design method aims to draw user attention to only the most essential elements. This helps the operator see and respond to issues more quickly and easily.
  • Data Analytics: Unlike SCADA systems that are specialized in data storage and analytics, HMIs are usually more limited. That said, today, HMIs can store historical data and present graphs and trends.
  • Cloud-based: The big HMI/SCADA brands support cloud-based applications with the help of edge computing to send data from the field to the cloud. There are a lot of security issues to solve to transfer data and information most securely.
  • Remote monitoring – today’s HMI enables remote monitoring that allows the user to monitor a system and respond no matter his location.
  • Edge capabilities: Edge HMIs started to pop up in the last few years. Concerning the cloud-based applications, the Edge HMIs send data from local HMIs to the cloud. This enables local control from the field and remote monitoring from the cloud.
  • IIOT – with the growth in device quantity in a control network, more IoT approaches have been taken. HMIs can collect and save more data and become a part of the IIoT network. For this reason, The use in IoT protocols are more widely used (MQTT, REST .etc)
  • Mobile devices – developing with the thought of responsive design. Web-based HMI
  • Security- Cyber security plays a big part in any control system today. The threats are real, and organizations face security issues every day. Every software and hardware has to be configured with maximum security. HMI security is mainly built into the system, but more devices like firewalls are needed. Also, the HMI application development has to consider security, like creating users and groups with password protection and implementing in-app limitations and privileges by users or groups.
  • AR – Augmented Reality
  • VR – Virtual Reality

HMI software Fundamentals

All HMI applications consist on:

  • Displays
  • Tags
  • OPC/ Driver connections
  • Alarms

HMI Brands

Giant companies are manufacturing and developing HMI and SCADA systems. Their HMI capabilities are very similar to each other. The leading brands in the market are:

  • Rockwell Automation – FactoryTalk View Machine Edition and Site Edition
  • Siemens – WinCC Flexible, WinCC Unified, WinCC (TIA Portal)
  • Inductive Automation – Ignition
  • Wonderware – System platform
  • GE – Cimplicity
  • Mitsubishi- GT Designer


You wanted to understand Human Machine Interface (HMI), and now you understand!

We discussed the fundamentals of HMIs, including the HMI definition, history, and uses. The difference between HMI and SCADA, and finally, the bright future of HMIs.

The next step for you is to dive into HMI programming.

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