Equipment used where flammable gases, vapors, mists, or combustible dusts may be present requires careful control of potential ignition sources.
One approach used in these environments is intrinsic safety. Rather than relying only on an enclosure or physical barrier, intrinsic-safety design limits the electrical and thermal energy available in relevant circuits so that the equipment cannot ignite the surrounding explosive atmosphere under the applicable operating and fault conditions.
For OEM engineers, this is an important system-level consideration. The LCD is only one component within the finished equipment, and the complete product must be evaluated according to the applicable standards, protection method, and certification requirements.
Focus LCDs supplies display modules for OEM equipment used in demanding and hazardous environments. We do not represent our LCD modules themselves as intrinsically safe or independently certified for intrinsic-safety applications.
What Is Intrinsic Safety?
Intrinsic safety is a protection method used for electrical equipment operating in potentially explosive atmospheres.
The principle is based on controlling the amount of electrical and thermal energy that could be released by the circuit.
IEC 60079-11 defines requirements for intrinsically safe apparatus and associated apparatus connected to intrinsically safe circuits. The standard applies to electrical circuits designed so that they are incapable of causing ignition of the surrounding explosive atmosphere under the conditions addressed by the standard.
For an OEM, this means intrinsic safety must be considered as part of the complete electrical system, not as a feature that can simply be added to one component.
Why Is Intrinsic Safety a System-Level Requirement?
An LCD does not operate independently.
The display subsystem may include:
- The LCD module
- Backlight
- Backlight driver
- Display controller
- Touchscreen electronics
- FPC cables
- Connectors
- PCB or PCBA
- Power conversion circuitry
- Batteries or power supplies
- Communication interfaces
All of these can affect the electrical characteristics of the complete system.
A display with low power consumption may be helpful in an intrinsically safe design, but low power alone does not make the LCD or finished equipment intrinsically safe.
The OEM must evaluate how electrical energy is supplied, stored, converted, and transmitted throughout the product.
How Does the LCD Affect an Intrinsically Safe Design?
The display can influence several areas of the system design.
Power Consumption
Power is one of the first considerations.
The display itself, backlight, controller, touchscreen, and associated electronics all contribute to the system’s total power requirements.
In applications where available electrical energy must be tightly controlled, engineers may prefer display configurations that reduce unnecessary power consumption.
This can influence decisions involving:
- Display technology
- Backlight brightness
- Backlight duty cycle
- Controller selection
- Touchscreen electronics
- Power-conversion circuitry
The appropriate configuration depends on the complete system rather than the LCD alone.
Backlight Considerations
The backlight can represent a significant portion of the power consumed by an LCD assembly.
For equipment with strict power limitations, engineers should determine how much illumination is actually required for the intended environment rather than automatically specifying maximum brightness.
Important considerations can include:
- Required luminance
- Available electrical power
- Backlight current
- Duty cycle
- Ambient lighting
- Viewing conditions
- Power-control strategy
A reflective or transflective monochrome LCD may reduce dependence on a backlight in some applications because ambient light can contribute to readability.
The correct approach depends on the equipment and operating environment.
Electrical Interfaces and Supporting Electronics
The interface between the display and the rest of the product also deserves careful consideration.
Depending on the LCD, the system may use:
- SPI
- I2C
- Parallel interfaces
- RGB
- LVDS
- MIPI DSI
- MCU interfaces
- Other control signals
The interface itself, controller circuitry, level shifting, power conversion, and supporting electronics can all affect the electrical design.
When equipment is being developed for an intrinsic-safety application, engineers should evaluate the complete display interface rather than looking only at the LCD panel’s nominal power requirement.
Stored Energy Matters
Energy can be stored in electrical components even when the average operating power appears low.
Capacitors, inductive elements, power-conversion circuits, and other components can store or release energy.
This is one reason intrinsic-safety analysis goes beyond simply measuring normal operating current.
The complete electrical design must be evaluated according to the applicable protection requirements and fault conditions.
Focus LCDs can provide information about the display module and help engineers evaluate display options, but determination of intrinsic-safety compliance belongs with the OEM and the appropriate certification or conformity-assessment professionals.
Intrinsic Safety Is Not the Same as Ruggedization
This distinction is important.
A display can be rugged without being intrinsically safe.
Features such as:
- Impact-resistant cover glass
- Environmental sealing
- Wide operating temperature
- Optical bonding
- Moisture resistance
- Dust protection
- Mechanical reinforcement
may improve a product’s suitability for demanding environments, but none of these characteristics automatically establishes intrinsic safety.
Likewise, a product designed for intrinsic safety may still need separate mechanical or environmental protection depending on where and how it will be used.
These requirements should be evaluated independently.
Moisture and Environmental Protection
Moisture, dust, chemicals, and other environmental contaminants can affect the reliability of electronic equipment.
The enclosure, seals, gaskets, cover glass, adhesives, and mechanical design may therefore be important parts of a product intended for industrial or hazardous environments.
However, environmental sealing should not be confused with intrinsic safety.
An enclosure that protects an LCD from moisture or dust does not by itself establish that the electrical system is incapable of creating an ignition source.
Both electrical safety and environmental protection may need to be addressed in the final equipment design.
Temperature Considerations
Temperature can affect both LCD performance and the surrounding electronics.
Every display has documented operating and storage temperature limits. Engineers should select a display appropriate for the expected environment and evaluate how the complete product manages heat.
However, a wide-temperature LCD should not be described as intrinsically safe simply because it can operate in extreme temperatures.
The OEM may need to consider:
- Ambient temperature
- Internal heat generation
- Surface temperatures
- Backlight heat
- Controller electronics
- Power circuitry
- Enclosure design
These factors should be reviewed as part of the overall equipment design.
For additional information about LCD temperature performance, see our LCDs with special temperature ranges article.
Why Adding a Heater Can Affect the Design
Some equipment operating in very cold environments may use heating elements to maintain acceptable internal temperatures.
A heater introduces additional electrical power and thermal energy into the system.
For equipment being developed around intrinsic-safety requirements, that additional energy must be considered as part of the overall design.
This does not mean heaters can never be used. It means they should not be added without considering their effect on the applicable electrical and thermal requirements.
Where practical, selecting an LCD whose documented operating range already supports the expected environment can reduce additional system complexity.
Touchscreens and Cover Glass
Touchscreens and cover glass can also influence the display assembly.
A touchscreen may add:
- Controller electronics
- FPC cables
- Connectors
- Additional power consumption
- Cover materials
- Adhesives
These components become part of the larger system that the OEM must evaluate.
Focus LCDs can integrate resistive or capacitive touchscreens, custom cover glass, optical bonding, adhesives, and other components into an LCD assembly when appropriate for the application.
Early coordination can help ensure these requirements are considered before the equipment design becomes fixed.
Monochrome LCDs for Low-Power Applications
Monochrome LCDs may be useful in applications where power consumption is an important design constraint.
Because Focus LCDs can customize monochrome displays at the glass level, engineers can specify characteristics such as:
- Dimensions
- Shape
- Resolution
- Segment layout
- Viewing mode
- Backlight
- Connector or FPC configuration
- Other assembly requirements
A custom segment or graphic monochrome LCD may allow an OEM to create the required user interface without using a more complex display architecture than the application requires.
That can be helpful in low-power designs, although the suitability of any particular configuration must still be evaluated as part of the complete equipment.
TFT Displays in Hazardous-Environment Equipment
TFT displays can also be incorporated into equipment intended for demanding environments.
TFT projects are customized differently from monochrome LCDs.
Focus LCDs does not modify the TFT glass itself. Instead, customization can be applied to components surrounding the TFT panel, including:
- Custom FPC cables
- Backlights
- Resistive or capacitive touchscreens
- Cover glass
- Optical bonding
- Adhesives
- Custom PCBs or PCBA when incorporated into the LCD assembly
The power and complexity of the complete TFT subsystem should be considered when the equipment has strict electrical-energy requirements.
More information is available on our custom display solutions page.
Who Determines Whether Equipment Is Intrinsically Safe?
The OEM responsible for the finished equipment must establish the applicable hazardous-environment requirements and work with qualified certification or conformity-assessment professionals when required.
The display supplier should provide accurate technical information about the display and its associated components.
Focus LCDs’ role is to help the engineering team select or customize the display portion of the system.
We do not certify the customer’s finished product, and the use of a Focus LCD does not by itself establish intrinsic-safety compliance.
Questions to Consider When Selecting an LCD
When a display will be incorporated into equipment with intrinsic-safety requirements, useful questions include:
- What electrical power is available to the display subsystem?
- Is a backlight required continuously?
- What brightness is actually necessary?
- Which controller and interface will be used?
- Are power-conversion circuits required?
- Will a touchscreen add electronics or power requirements?
- What operating temperature range is required?
- Are heaters or other thermal-control components planned?
- What mechanical or environmental protection is required?
- How long is the equipment expected to remain in production?
- Which display characteristics will be difficult to change after qualification?
Addressing these questions early can help the OEM evaluate the display alongside the rest of the electrical and mechanical design.
Plan the Display Early in an Intrinsically Safe Design
For equipment being developed around intrinsic-safety requirements, the display should be selected early enough for its electrical and mechanical characteristics to be considered in the overall architecture.
Waiting until the enclosure, power system, PCB, and certification strategy have already been established can unnecessarily limit display options.
Focus LCDs works with OEM engineering teams to evaluate display technology, power requirements, backlights, interfaces, touchscreens, cover glass, customization, and lifecycle needs.
Contact our engineering support team to discuss the display requirements for equipment intended for a demanding or hazardous environment.
Reference
IEC, IEC 60079-11:2023, Explosive atmospheres – Part 11: Equipment protection by intrinsic safety “i.”
