Recent advancements in industrial automation have led to the development of more powerful and more flexible control systems, which are easier to program, configure and communicate with. Modern industrial controllers are characterized by higher processing power and better interconnectivity in comparison to traditional controllers.

Today, many industrial control applications utilize Human Machine Interfaces (HMIs) and Industrial Personal Computers (IPCs) to acquire raw data, process, visualize or store the processed data. You’ll often find both HMI and IPC on the factory floor, and it is almost impossible to distinguish them at first glance; as they resemble each other in physical appearance. Even many plant operators usually call an IPC an HMI, which adds to potential confusion.

However, there are technical and functional differences between an IPC and an HMI that go beyond their outward physical design. These differences include processing and connectivity capabilities, feature set, levels of software flexibility for modification purposes or functionality addition, and overall performance. This quick read article explores the basics of IPCs and HMIs, as well as the main differences and similarities between the two.

What is an Industrial PC(IPC)?

Think of an Industrial PC in terms of your laptop or desktop computer; as they basically have the same technical characteristics and features including a Microprocessor (CPU), storage media, RAM type, interface ports, overall performance…etc. An IPC has similar software functionalities as a normal PC; as you can install software packages and perform all programming tasks as you do on your laptop. However, the programming functions of Industrial PCs are similar to those of Programmable Logic Controllers (PLCs). Though IPC controllers have more memory and better processors than PLCs and even some Programmable Automation Controllers (PACs), as they run on PC platforms.

But unlike a normal PC, an IPC is a ruggedized PC system, which is well-suited for use on the factory floor. Industrial PCs are specifically designed to withstand harsh industrial environments characterized by extremes of temperatures, humidity, power surges, and mechanical shocks or vibration. Their rugged nature also protects them from excessive dust, moisture, debris, or fire damages. Industrial PCs were first developed in the 1990s, with automation providers designing a control software that emulated a PLC environment but running on standard PCs. These first attempts of using normal PCs for industrial automation were often unreliable, as the PC controllers were subject to problems of an unstable host OS (Operating System) and high failure rates of the non-industrialized PC hardware.

Since then, there have been numerous advances in IPC technology including the use of more stable Operating Systems, hardened industrial PCs, with some manufacturers developing customized IPC systems with real-time kernels for specific automation tasks. The real-time kernel allows the automation environment to be separated from the OS environment and it takes priority over the Operating System for control tasks, such as Input/Output interfacing.

Features of Industrial PCs 

IPCs used in the automation field are characterized by the following features: 

A) Wider Range of Operating Temperatures: Appropriately deployed Industrial PCs are rated to operate in environments with up to 60°C temperatures, and in some extreme applications, they can work reliably in temperatures of up to 85°C. Also, even though cold settings are not usually taken into account when selecting controllers, some IPCs are built to work in automation systems operating in subzero temperatures. 

B) Durable Metal Frame and Enclosure Construction: This is a critical feature that ensures the operability of IPCs even in tough environments. The enclosure and frame design also determine the type of mounting required for the IPC. 

C) Better Resistance to Vibration and Overall Mechanical Endurance: IPCs are normally mounted on shock absorbers, which provide cushioning and mechanical isolation. For this reason, IPCs are being widely used in applications with high levels of vibration, such as in Laser-Guided Vehicles (LGV) and mobile equipment. They are growing in popularity in systems operating outdoors, in which shock resistance is paramount, in case of unexpected collisions. 

D) Isolation from Electromagnetic Interference (EMI) or RFI: The electrical design of Industrial PCs provides proper isolation assurance and is compliant with internationally recognized electrical standards such as the NEMA (National Electrical Manufacturers Association) standards. During installation, IPCs are also properly grounded with better electromagnetic shielding, to counter Electromagnetic Interferences (EMI) and high radio frequencies (Radio Frequency Interference-RFI). Hence, IPC systems can operate reliably in environments with high levels of EMI or RFI, such as those with large motors or high voltage lines; with little to no impact on the system’s integrity for data transmission or communication issues caused by interferences. 

E) Better Voltage Surge Protection: Voltage spikes, transients, surges, and electrical noise on AC power lines are very common on the plant floor. For this reason, IPCs are equipped with better voltage surge protectors. 

F) Higher Level of IP Rating: Industrial PCs are characterized by a higher rating of Ingress Protection (IP), compared to normal PCs. A high IP rating provides protection against contaminants such as tools, moisture, and dirt; with IP65 being the standard on all IPC displays for water and dust resistance. 

G) Better Protection against Humidity and Dirt: Humidity and dust accumulation can affect the internal components of any PC. But with the advanced cooling fans and ventilation systems used in factory floors, IPCs can operate well even in humid and dusty conditions with little or no maintenance. As ventilation systems allow consistent airflow inside the IPC chassis, and special filters are also provided to keep out dust and similar contaminants. So, you can comfortably use an IPC in facilities with high concentrations of dust like in paper mills, as long as the facility is well ventilated. 

Applications supported by an IPC 

Basically, IPCs are used in all typical industrial segments to perform various functions including: 

  • Data acquisition for automatic machine-tool control, Statistical Process Control, and Gauging applications. 
  • As stand-alone or networked controllers for monitoring, data collection and control tasks. 
  • Motion control and handling equipment. 
  • In cell manufacturing as cell controllers. 
  • General industrial automation tasks like in smart factories. 

What is an HMI? 

A Human-Machine Interface (HMI) is software and hardware through which a human operator interacts with a controller. Allowing the operator to monitor the state of a machine or process under control, change the control objective by modifying the control settings, and manually override the automated control operations in case of an emergency. The HMI software is normally driven by the selected hardware such as Operator Interface Terminal (OIT), PC-based or in-built PC. That’s why HMI technology is sometimes referred to as Operator Terminal (OT), Local Operator Interface (LOI), or Operator Interface Terminal (OIT), or Man-Machine Interface (MMI). Often, selecting the best hardware simplifies the development of the HMI software.

The HMI software enables human operators to manage and control industrial machinery and processes through a computer-based Graphical User Interface (GUI), which provides visualization capabilities. Available HMI software is classified into two basic types namely Machine Level and Supervisory Level. The Machine Level software is in-built in machine-level devices within the plant facility itself.

While the Supervisory level HMI software is designed for the plant’s control room and is also used in SCADA (Supervisory Control and Data Acquisition) systems- a process control application that gathers data from input devices within the plant floor and transmits the information to a centralized computer for processing. The HMI software is mostly designed for either machine-level or supervisory level control applications, but there are some applications that use both types of HMI software. Though these dual-HMI software applications tend to be more expensive, they eliminate system redundancies thus reducing long-term costs.

Common Applications of HMI 

Technically, the term HMI can be applied to any screen(hardware) which allows users to interact with a machine, system, or control devices, but in most cases, HMI is used in the context of industrial automation. Industries that are currently using HMI technology include Energy, Oil and Gas, Transportation, Food & Beverage, Manufacturing, Water and Waste Water, Recycling, and many more. Hence, almost all industrial organizations utilize HMI technology, to perform the following tasks.

  • HMIs are purpose-built pieces of hardware communicate with Programmable Logic Controllers (PLCs) and Input/Output devices via predefined communication protocols. The HMI then displays the gathered information and data for users to view, you can think of it as a monitor for the PLC. In this aspect, HMI screens can be used to perform standalone control functions like monitoring and tracking, or more complex operations such as switching machines off, depending on how the HMI software is implemented. For example, in an industrial setup, HMIs can be used to monitor inputs and outputs from machines, visually display control data, track production time, tags and trends, and oversee Key Performance Indicators (KPIs).
  • HMI can be used to optimize industrial processes like increasing production speed, by digitizing and centralizing controller data for an operator. Hence, by leveraging HMI technology, operators can analyze information displayed in charts, graphs, or digital dashboards, view and manage process alarms, and connect with MES (Manufacturing Execution Systems) and SCADA systems, all through one console. Previously, operators were required to constantly walk to the plant floor to review mechanical progress and record it on paper sheets or a whiteboard. But since PLCs can communicate real-time data directly to an HMI display, the HMI technology has now eliminated the need for the previous outdated technology; thereby reducing costly problems associated with human error or lack of information.
  • The HMI also allows system integrators, operators, or control system engineers to configure control algorithms or control setpoints and parameters in the PLC controller. The HMI then displays historical and process status information, which the aforementioned roles can use to review and monitor processes, diagnose problems, send control commands, as well as establish and adjust the set parameters in the controller. Just like how you interact with your air-conditioning system to check and control temperature, a plant-floor operator can also use an HMI to check and control the temperature variations of an industrial process like metal curing.

What Distinguishes an Industrial PC(IPC) from an HMI? 

A) Processors: Industrial Computers are equipped with higher performance processors (CPUs) such as Intel Core i- Processor Series and more Gigabytes of RAM since they operate on PC platforms. For this reason, they have more processing power, more mass storage space, and more system memory (RAM) than traditional HMI. HMIs mostly utilize slower CPUs, as they do not need a lot of “reserve” processing power to accommodate other software packages or control tasks; this is because they are either designed for Machine Level only or for Supervisory Level only tasks. Most HMI manufacturers have to balance the needed performance with the manufacturing costs, so as to get an acceptable compromise in the HMI hardware design to accomplish the task at hand.

B) Operating Software (OS): Industrial PCs (IPCs) run on an open Operating System (OS), which allows you to install any type of software you may need from any vendor. Also, when changing or upgrading your IPC hardware you’ll not be required to rewrite your software, as all IPCs utilize a common Windows-based OS. However, the biggest advantage of IPC systems (the open OS) is also their greatest potential disadvantage. As their open operating system leaves them vulnerable to malware, viruses, or ransomware; if a malicious software or virus was to find its way into the IPC via the internet or USB stick. Hence, good IPC hardware and software protection must be in place, and it should be regularly reviewed and updated. That’s why Windows 7 OS is no longer recommended for new IPCs as it is no longer receiving security fixes, patches, or updates from Microsoft. Although older IPC systems may still run-on Windows 7 OS, which would make them highly vulnerable to the aforementioned security threats; if left connected to the internet without proper and reliable protection such as additional hardware firewalls.

On the other hand, HMIs are usually proprietary with closed, small foot Operating Systems. This means that HMI hardware is only compatible with the HMI design software specified by the manufacturer. Typically, most of the HMI design software packages you will find in the market are not compatible with each other. So, a given HMI is only designed to work with select PLCs and other devices from the same vendor. A strategy that locks HMI users into one manufacturer. While a captive audience is certainly advantageous for the HMI manufacturer, it may be disadvantageous for the HMI user.

For example, third-party connectivity can be a challenge with HMI, especially because not all PLCs and communication protocols are seamlessly compatible with every HMI firmware. Also, you cannot install any additional software packages on HMI, as HMI manufacturers lock the OS at the factory providing only the runtime for the visualization software. The advantage of using only one HMI design software is that you cannot introduce malware or viruses to the HMI OS that easily, as with IPCs. Also, an HMI does not require a formal shutdown like an IPC.

C) Display Screens: IPCs have larger display screens that allow more information or data to be displayed at one single instance while providing a wider view for the operator checking the data. Whereas, traditional HMIs often cover display screens of smaller sizes from about 4 inches to 12 inches, although HMI manufacturers are now providing larger screens for use in high-end applications only. 

D) Communication Interfaces: IPCs provide plentiful communication interfaces such as multiple USBs, dual Ethernet ports, and/or serial ports which allow more hardware connections and assist in future-proofing applications much more easily compared to traditional HMI. Also, IPCs are Windows-based and PC-based visualization tools that provide greater flexibility, enabling integration with other communication protocols and applications compatible with the operating system. However, this flexibility is not achievable with traditional HMIs, as they rely on specific communication protocols and application software. Older versions of HMI software used specific serial communication protocols such as DeviceNet, MODBUS RTU, or PROFIBUS. Whereas new versions of HMI utilize specific Ethernet-based communication protocols such as EtherNet/IP, OPC DA/UA, Modbus TCP, PROFINET, and many more.

E) Technology Upgrades: As technology advances, there will always be a need to expand the hardware. Hardware expansion in IPCs is much easier and more cost-effective than in HMIs. As with HMI, you cannot transfer HMI visualization projects from one vendor to the other if there’s a need to expand the hardware. In such a case, to move your HMI project, you will be required to recreate the visualization application you’re using from scratch. That in turn would increase the development time and costs, not forgetting that this will complicate the support aspect once the automation system is deployed. 

What are the Similarities between IPC and HMI? 

  • Some of the latest versions of HMI such as the HTML5 web panel have significantly tried to blur the line between IPCs and HMIs, as they no longer rely on specific PLC models or communication protocols for connectivity. Instead, they utilize the open HTML5 protocol which allows them to easily connect to a web server via an IP address, the same way a web browser on an IPC would connect to a website. With this connection, the HMI web panels are not only capable of connecting to different PLCs, but also to other devices having integrated web servers. A good example is the HMI display of diagnostic or configuration page in an IIoT-enabled Variable Frequency Drive (VFD). 
  • Both Industrial PCs (IPCs) and Human-Machine Interfaces (HMIs) are industrial hardware, designed for harsh industrial environments. Also, their rugged nature provides more mechanical protection against extreme heat, mechanical shock, or vibration.
  • Often, HMIs range from physical control panels with indicator lights and buttons to industrial PCs running a dedicated HMI software with color graphics display. Hence, a typical industrial PC can serve as an HMI, when it is dedicated to running HMI design software. The IPC with the HMI software can then be mounted on the control panel the same way an HMI hardware is mounted. 


At first glance, IPCs and HMIs may look the same in physical appearance, but they have fundamental differences in performance, processing capabilities, and software flexibility. They both have specific advantages and disadvantages, but the two are widely used in industrial automation systems. Therefore, depending on the specific needs of your application, you can determine whether an IPC or an HMI will be the best fit, based on factors such as performance, screen size, and feature set.

Note, the more features you add to an HMI system, the closer it edges the performance capabilities, visualization concept, and feature set of an IPC-based system, as with HTML5 web panel HMI. For more information or to discuss which PLC Control and Instrumentation solution might be best for your application, please visit our website here, or contact us at sales@dosupply.com or 1-800-730-0292.

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