HMI hardware variations often feature compact control electronics integrated with ruggedized display screens or touchscreens. These displays may include liquid-crystal display (LCD) options with tempered glass and cast-aluminum frames or high-definition backlit light-emitting diode (LED) screens, showcasing the diversity in HMI hardware variations.

In particular, HMI hardware variations designed for outdoor use or indoor plant applications exposed to oil, dirt, and machining byproducts come equipped with fully sealed enclosures, highlighting the adaptability of HMI hardware to various industrial environments.


Among the HMI hardware variations, resistive touchscreen displays stand out as a popular choice, providing operators with an intuitive interface for machine interaction. These systems use thin-film transistor (TFT) liquid crystal displays (LCDs) in one of two variations. In short, resistive touchscreen technology senses physical flexing of the touch surface.

The screen has two transparent, conductive layers with a uniform resistance. These layers are very close together but do not touch until pressure is applied — like when an operator uses a finger or stylus.

This pressure causes the two layers to connect, the outer layer flexes into the inner layer at that location and that in turn causes electricity conduction that’s detected by the screen’s onboard electronics.

Such HMI hardware variations are especially useful in environments like packaging or healthcare, where operators often wear gloves. With resistive touchscreens, there’s no need to remove these gloves, making it easier and more efficient to use the HMI.

Maple Systems offers HMIs, HMIs with local IO, and Industrial Panel PCs with Resistive touchscreen technology (ranging from 4.3” to 21.5”).

Screen of the HMI5100Bv2

The wide-screen HMI5100Bv2 provides a high-quality unit for applications requiring straight-forward HMI functionality at a great price. Paired with our free software, this operator interface is an exceptional value. 

Screen of the OMI6808B

With a solid state platform and fanless cooling system, this 8” resistive touchscreen IPC is ideal for space-constrained applications. The OMI6808B provides a high-quality option for applications requiring UL and a Windows® Operating System. 


Capacitive touchscreen displays represent another significant HMI hardware variation, leveraging thin-film-transistor (TFT) technology to offer enhanced interactivity similar to that found in many of today’s consumer smartphones. This technology is now increasingly common in industrial HMI systems due to its affordability and the industry’s growing preference over resistive touchscreens.

There are two different types of thin-film-transistor (TFT) liquid- crystal (LCD) capacitive touchscreen options for industrial HMIs. Their adoption has expanded HMI use in industries needing bezel- free designs, mostly because they help machinery meet cleanliness and sterility requirements. In addition, capacitive touchscreens extend field life — because they don’t use on-display pressure points to form the circuit, so they’re not vulnerable to the wear and decreased sensitivity some resistive displays exhibit over time.

  1. Surface Capacitive Touchscreens: An established technology, these screens feature a transparent, conductive layer, often referred to as the electrode film, positioned right beneath an insulator layer. A small voltage applied across this conductive layer generates a consistent electrostatic field. When a conductive object—such as a user’s finger or a stylus—makes contact with the insulator’s outer surface, it causes a localized drop in voltage within the electrode layer at the point of contact. This change is detected by the HMI, allowing for direct, reliable touch interactions. Surface capacitive touchscreens are valued in HMIs for their durability and dependable touch response, making them ideal for a variety of industrial applications.
  2. Projected Capacitive Touchscreens (PCT): Representing a more sophisticated advancement, PCT screens support complex multi-gesture functions, including swiping, zooming, and pinching. This technology employs a similar conductor layer to that used in surface capacitive screens but adds a crucial element—a secondary electrode layer, with its rows of electrodes set at right angles to those in the first layer. This configuration creates a precise grid of intersecting electrodes. Touching the screen with a conductive object disturbs this grid’s voltage, allowing the HMI to accurately detect and interpret various gestures. PCT screens are favored for enabling enhanced gesture recognition, significantly improving the user experience in more advanced HMI applications.

These capacitive touchscreen technologies offer tailored advantages for HMIs, from the robust, straightforward interaction provided by surface capacitive screens to the sophisticated, gesture-responsive functionality of PCT displays. This adaptability ensures that regardless of the industrial environment or application, there’s a capacitive touchscreen solution that can meet the unique demands of any HMI system.

Maple Systems offers HMIs, Industrial Panel PCs, and Industrial Monitors with Capacitive touchscreen technology (ranging from 15.6” to 21.5”).

HMI Screen of the cMT3152Xv2

The cMT3152Xv2 features a powerful CPU, remote access capabilities, IIoT functionality, and our most advanced feature set, making this capacitive touch panel a powerful solution for your application.

HMI Screen of the PC1317APH

This sunlight readable fanless industrial computer features a 17” capacitive touchscreen, steel chassis, aluminum heatsink, and the option of VESA or panel mount making it extremely rugged and versatile.


The advanced functionality of Projected Capacitive Touchscreen (PCT) technology enhances user interaction with industrial HMIs. It allows users to fully utilize the graphical elements on the screen. For example, executing a comprehensive five-finger pinch can instantly return the user to the HMI home screen. Similarly, a three-finger swipe facilitates smooth navigation through menus, diminishing the dependence on home screen icons for navigation. Moreover, swiping upward from the bottom of the display grants easy access to a global settings menu, significantly streamlining user interaction.

Additionally, PCT-based HMIs elevate the user experience with haptic feedback mechanisms. These mechanisms, through vibrations and pulses, provide instinctive confirmation of touch commands to operators. This feature proves invaluable in enhancing operational precision and user satisfaction.

Moreover, advancements in material science have enhanced capacitive touchscreens with solid glass, improving their durability, chemical resistance, resolution, and clarity. Unlike resistive touchscreens, capacitive screens withstand wear, impact, and harsh cleaning agents better, ensuring greater durability and reliability over time.

Considering this, the widespread use and intuitiveness of capacitive touchscreen technology in consumer electronics have made its operation universally familiar. This familiarity, along with the touchscreens’ inherent intuitiveness, greatly reduces the learning curve for using these HMIs. As a result, they are favored in a wide range of industrial applications.


A novel development among HMI hardware variations is the emergence of devices without built-in screens, often referred to as headless or virtual HMIs, reflecting a shift towards more flexible and integrated control solutions. These devices, often described as headless, faceless, or virtual HMIs, and sometimes as DIN-rail HMI modules, represent a paradigm shift towards more adaptable and integrated control mechanisms. They are especially suited for scenarios that demand remote access or specialized user interfaces, eliminating the necessity for conventional screens.

Headless HMIs and Industrial Box PCs can connect to the internet via Wi-Fi. This connectivity allows for data exchange with authorized smartphones and tablets. However, this feature requires user-friendly GUIs. These interfaces must combine diagrams, schematics, and text to present machine data effectively. The more tailored these GUIs are, the more helpful they become.

Example of a headless HMI options from Maple Systems:

This headless HMI provides a high-quality option for applications requiring straight-forward HMI functionality without a touchscreen. The cMT-SVR-100 is tailored for remote accessibility, monitor PLC operations, gather data, and remotely access your control system via the cMT Viewer App on your smart phone, tablet, laptop, or PC.


Besides that, headless HMIs offer flexible display solutions. They can connect to large, commercially available industrial monitors using a standard HDMI cable. This setup is ideal when management wishes to display important data on a large screen for plant personnel. It helps share information about production throughput or machine alerts efficiently. 

Furthermore, headless HMIs can integrate with industrial PC-based controls. This integration ensures relevant data reaches those who need it, allowing multiple users (including maintenance technicians, supervisors, operators, and company owners) to access specific machine information tailored to their roles. This approach not only enhances operational efficiency but also supports a more informed decision-making process, demonstrating the flexibility of HMI hardware variations.

Example of an industrial monitor options from Maple Systems:

This fanless extended temperature Industrial Monitor features a high-brightness/sunlight readable (1000 nits) projected capacitive touchscreen and is a great value.


Headless HMIs offer several compelling advantages. Firstly, they are notably cost-effective. With prices for standard models falling below a thousand dollars, they stand as a financially smarter choice compared to traditional HMI setups that may feature seldom-used screens.

Secondly, these innovative devices empower machine operators with the capability to manage multiple machines at once. By utilizing a mobile device, operators can seamlessly monitor and control machinery as needed. This not only introduces a new level of operational flexibility but also significantly boosts efficiency.

An additional advantage is the mobility it grants maintenance personnel. Unlike traditional HMIs, which are fixed in one location, headless HMIs allow maintenance staff to move freely around the facility. This mobility is crucial for efficiently diagnosing and troubleshooting large machinery issues, such as sensor, switch, motor, or other component malfunctions, without the need to constantly run back and forth between different parts of the production line.


Open Source HMIs, particularly those integrated with Industrial PCs, have become a fundamental part of modern control systems. It’s fascinating to note how design engineers now often equate HMIs with self-contained Industrial PCs. These systems, typically fanless and running on operating systems like Linux or Windows, are built on a single circuit board. Their complexity and the inclusion of extensive electronics and software make them more expensive than some alternatives.

Yet, over the past twenty years, these systems have become standard. They combine HMI features with PC-based control on one microprocessor. Recently, Industrial PCs got upgrades. They now have dual and quad-core processors (1 and 1.6-GHz). This boosts system integration but keeps HMI and control tasks separate. This setup is great for complex motion and automation jobs.

These PC-based HMIs embody a versatile design philosophy, allowing for the expansion of system functionalities as needed. This guide will later delve into how such systems not only manage machine control but also integrate digital and analog I/O for comprehensive automation and enterprise-level system management.

The evolution of control functions within HMI technology mirrors the foundational structure of traditional PCs, centralized around a processor and an operating system managing various resources, including visual display capabilities. Integrating a PC for industrial display management introduces no extra costs, thanks to the streamlined production of flat-format PC components. This approach results in an efficient, cost-effective solution combining touchscreen interface and control electronics in a single package.

Additionally, Industrial PCs improve system reliability. They do this with better fault and diagnostic communications. They also adjust machine functions for maintenance and offer strong network connectivity. The broad use of Industrial PCs shows their importance. These PCs combine touchscreen interfaces with control electronics, aiding complex industrial tasks.

Maple Systems offers Industrial Panel PCs in sizes ranging from 7.0” to 21.5”. You can pair one of our Industrial Box PC with one of our Industrial Monitors for maximum flexibility.


As technology advances, it’s easy to get caught up in the latest trends in Human Machine Interface (HMI) hardware. However, traditional forms of HMI, like Operator Interface Terminals (OITs), still play a crucial role in industrial and commercial settings. Particularly for newer engineers, the ubiquity of touchscreen interfaces in both our professional and personal lives might obscure the importance of traditional industrial touchscreen HMI formats.

OITs serve as a noteworthy option, often considered alongside other HMI technologies. Characterized by their durable aluminum enclosures, these devices are equipped with an alphanumeric keypad and a compact, rectangular display. The display, typically an LCD or VFD, presents information in bright monochrome, capable of displaying a few lines of text or numerical data relevant to machine operations.

Despite their simple appearance, OITs pack a punch in functionality, relying on modest internal processing power. They connect to external controls, like PLCs, for enhanced capabilities, bridging simple interfaces with complex machinery operations. Communication is primarily facilitated through an RS-232 connection, allowing for both programming inputs and manual control through the keypad, often using straightforward ASCII text for ease of use.

The choice between Liquid Crystal Display (LCD) and Vacuum Fluorescent Display (VFD) in Operator Interface Terminals (OITs) hinges on the specific operational environment and visibility requirements.

Backlit LCD OITs are particularly suited for normal lighting conditions, offering ruggedness and reliability across a wide range of temperatures, from -10°C to 65°C. These displays can come in 2 or 4-line configurations, accompanied by a 6 to 24-key keypad. They also feature a custom slide-in legends option for easy customization according to specific application needs. Designed to be durable, LCD OITs are also Class I, Division 2 certified, making them safe for use in certain hazardous environments.

On the other hand, VFD OITs shine in scenarios where a crisp, high-contrast display is essential. They have inherent light-emitting qualities, making them superior in low-light conditions. This ensures the display stays clear and readable, no matter the ambient lighting. Like LCDs, VFD OITs operate within the same temperature range. They feature similar display lines, keypads, and customization options. Additionally, they meet Class I, Division 2 safety standards.

Both technologies offer their unique advantages, making them suitable for a variety of industrial settings. Whether the priority is visibility in variable lighting conditions or reliability across temperature extremes, there’s an OIT configuration that meets the need.

In conclusion, Operator Interface Terminals continue to be an invaluable component in the vast landscape of HMI technologies. Their straightforward design and reliable functionality ensure that they remain a vital tool in industrial settings, complementing more advanced systems. For professionals entering the field, understanding the role and capabilities of OITs is essential for grasping the full spectrum of HMI solutions available today.

Examples of OIT from Maple Systems with LCD or VFD displays, and programmable keys.

This OIT features a 2-line by 20-character LCD display and a customizable membrane keypad with 24 programmable keys for tailored control and clear information presentation.

This OIT showcases a 4-line by 20-character VFD display for enhanced visibility, complemented by a customizable membrane keypad with 16 programmable keys.