When building a Raspberry Pi or other embedded measurement system, the display is often treated as a secondary component. In practice, choosing the wrong LCD can create problems with readability, system compatibility, temperature performance, or long-term operation.
For a measurement instrument, I usually recommend looking at the display from the system level rather than choosing one based only on screen size.
Start with the Information You Need to Display
The first question should be: what will the operator actually see?
A simple measurement device may only need to show:
- Numerical readings
- Units
- Status indicators
- Basic menus
- Warning messages
A more advanced system may need to display several measurement channels, graphs, waveforms, historical values, or a more complex graphical interface.
This directly affects the required resolution and screen size.
For example, a small display may be perfectly adequate for a compact temperature or voltage monitoring device. If the interface needs to show multiple graphs and detailed data at the same time, a larger and higher-resolution LCD may provide a much better user experience.
Screen Size Should Match the Equipment
It is tempting to select the largest display that fits the budget, but this is not always the best approach.
The physical enclosure, viewing distance, mounting position, and amount of information on the interface should all be considered together.
For a compact embedded instrument, a smaller TFT LCD module can help keep the overall enclosure size under control. For a production-line testing system, a larger display may make detailed information easier to read from a normal working distance.
The display should therefore be selected together with the mechanical design rather than treated as an independent component.
Resolution Is Important for Measurement Data
Measurement interfaces often contain small numbers, decimal values, units, tolerance limits, and graphs.
If the resolution is too low, the interface can become crowded. Increasing resolution can improve the definition of text and graphical elements, but the system processor and display controller also need to support the selected resolution.
For an embedded project, I would check:
- Native LCD resolution
- Processor or SBC display capability
- Graphics performance
- Interface bandwidth
- UI complexity
A higher resolution is useful when the application genuinely needs more detail. It is not automatically better for every measurement instrument.
Brightness Depends on the Installation Environment
Brightness should be selected according to the actual environment.
An LCD used inside a laboratory or factory with controlled lighting normally has different requirements from one installed near a factory entrance, window, or semi-outdoor monitoring cabinet.
For brighter environments, engineers may need to consider:
- Backlight brightness
- Contrast
- Anti-glare treatment
- Optical bonding
- Sunlight readability
The goal is not simply to select the brightest LCD available. Excessive brightness can increase power consumption and may not provide meaningful benefits in a controlled indoor environment.
Don’t Ignore Operating Temperature
Temperature is particularly important for equipment that may operate outside a controlled office environment.
Industrial measurement equipment can be installed in factories, workshops, warehouses, outdoor cabinets, or other locations where the ambient temperature changes considerably.
Temperature can affect LCD characteristics such as response time, contrast, backlight performance, and long-term reliability.
For this reason, the LCD’s specified operating temperature range should be compared with the actual environmental requirements of the equipment.
If the equipment may experience low or high temperatures, selecting a display with a wider temperature range can reduce the risk of display performance problems during operation.
Check the Interface Before Ordering
One of the easiest mistakes to make is selecting an LCD based on size and resolution without checking the interface.
Common interfaces for TFT LCD modules include RGB, LVDS, MIPI and eDP. The correct choice depends on the processor, controller, resolution, cable requirements and system architecture.
For an embedded measurement project, I would verify:
- Processor/SBC display output
- LCD interface type
- Resolution supported by the hardware
- Cable length
- Connector type
- Signal integrity requirements
- EMI considerations
This is especially important when integrating a custom LCD into an existing controller board. A display with attractive specifications may still be unsuitable if its interface cannot be directly supported by the system.
Viewing Angle Can Matter More Than Expected
If the operator always looks directly at the display, standard viewing characteristics may be sufficient.
However, measurement equipment installed on a production line or shared workstation may be viewed from different angles.
In those cases, a wider viewing angle can make numerical values and graphs easier to read without requiring the operator to stand directly in front of the panel.
IPS-based LCD technology can be worth considering when viewing consistency is important.
Touch Panel or Physical Controls?
Some measurement systems use buttons, rotary controls, or keyboards, while others use a touch panel interface.
A touch panel can simplify menu navigation and provide a more flexible interface, but it also introduces additional integration requirements.
When considering a touch panel, engineers should evaluate:
- Glove operation requirements
- Protective glass
- Surface durability
- Controller compatibility
- Touch interface
- Environmental conditions
For equipment that will mainly display information and use physical controls, adding touch may not be necessary. For systems with complex menus and configuration screens, touch interaction can be useful.
Reliability Should Be Considered Early
For a prototype, it may be easy to focus on getting the display working quickly.
For a production product, however, display reliability should be considered during the initial component-selection stage.
Important factors include:
- Operating temperature
- Backlight lifetime
- Interface stability
- Mechanical integration
- Continuous operating requirements
- Availability of replacement units
A display that works well on a development bench may not necessarily be the best choice for equipment expected to operate continuously in a factory environment.
A Practical Selection Checklist
Before finalizing an LCD for an industrial measurement project, I would make a short specification checklist:
- What information needs to be displayed?
- What screen size fits the enclosure?
- What resolution does the UI require?
- How bright is the installation environment?
- What operating temperature range is required?
- Which interface does the controller support?
- What viewing angle is needed?
- Is a touch panel necessary?
- Will the equipment operate continuously?
- Is the selected LCD available for long-term production?
These questions can eliminate many compatibility problems before the hardware reaches the prototype stage.
I also found this detailed reference useful when comparing these factors: LCD display selection guide for industrial measurement equipment.
For anyone working on a Raspberry Pi-based measurement instrument or another embedded HMI, I would be interested to hear which LCD interface and screen size you have found easiest to integrate.