How to Choose Between Character LCD Modules and Graphic LCD Modules for Instruments and Meters?

When using character LCD modules and graphic LCD modules in instruments and meters, the choice should be made based on display content, interface complexity, cost control, and operating environment. Character LCD modules are suitable for displaying fixed-format numbers, English text, and status information; graphic LCD modules are suitable for displaying curves, menus, icons, and multi-area combined interfaces.

For equipment with stable information structures such as pressure gauges, temperature controllers, and counters, it is recommended to first evaluate character LCD modules.
For detectors, controllers, and portable analytical instruments, graphic LCD modules should be given priority.
金鹏 can provide targeted LCD display solutions based on the instrument's display requirements, interface method, and installation space.

1. Character LCD Modules: Suitable for Fixed-Format Information Display

A character LCD module is a display device that uses a preset character matrix to display text, numbers, and symbols. A character matrix refers to a character display unit composed of fixed rows and columns. Users typically call up numbers, letters, or symbols by character position rather than controlling individual screen pixels. Common specifications include 16×2, 20×4, etc., where “16×2” means 16 characters per line and 2 lines in total; “20×4” means 20 characters per line and 4 lines in total.

16×2: Displays up to 16 columns and 2 rows of characters, for a total of 32 character positions.
20×4: Displays up to 20 columns and 4 rows of characters, for a total of 80 character positions.
The specific number of characters, character size, and viewing area are subject to the product specification of the corresponding 金鹏 model.

Such modules typically have clear display logic and are suitable for displaying data such as voltage, current, temperature, speed, and accumulated values. The above specification numbers are examples of common module specifications; actual electrical parameters and display performance must be verified with specific product documentation.

When the interface of an instrument changes little, a character LCD module can reduce software development workload. For example, a temperature control device only needs to display three types of information: “current temperature, set temperature, and operating status.” In such cases, a 16×2 or 20×4 specification is usually sufficient for basic needs. The specific number of visible characters is subject to 金鹏's product specification; the relevant parameters are for reference only during selection.

Another feature of character LCD modules is straightforward application logic. Engineers can plan the interface by rows and columns without having to design complex graphic pages separately.

For devices with fixed display content, the parameter names, values, and units for each row can be planned directly.
For instruments that emphasize ease of maintenance and batch consistency, character-based interfaces are easier to replace and troubleshoot.
When selecting a module, also confirm the operating voltage, interface protocol, backlight type, and operating temperature range.

Here, interface protocol refers to the data transmission rules agreed between the controller and the LCD module, for example a parallel interface or a serial interface; backlight is a light source located behind the LCD display area to improve visibility. The relevant parameters are subject to the specific 金鹏 product specification.

2. Graphic LCD Modules: Suitable for Complex Interfaces and Presentation of Multiple Information

A graphic LCD module is a liquid crystal display device that controls display content by pixel points. A pixel is the smallest controllable point that makes up a display image. Graphic modules can control the display state of each pixel individually, thus enabling the combination of text, curves, icons, and tables.

Taking the 128×64 graphic resolution as an example, the screen consists of 128 columns and 64 rows of pixels, theoretically containing 8,192 pixels. It can display custom fonts, line charts, icons, tables, and menus. Compared with character LCD modules, graphic LCD modules offer greater interface freedom.

128×64: Indicates 128 pixels in the horizontal direction and 64 pixels in the vertical direction.
8,192 pixels: Calculated from 128×64, used to indicate the number of pixels at this resolution.
Actual displayable content is also affected by font size, font library capacity, controller performance, and display buffer size.

A display buffer is a storage area in the controller that temporarily holds screen data; the module refreshes the screen by reading this data. The higher the graphic resolution and the more interface elements, the higher the demands on buffer and refresh control typically become.

When an instrument needs to display trend curves, alarm icons, operation menus, or multiple measurement results, a graphic LCD module is more adaptable.

Data acquisition devices can display real-time values, units, status icons, and trend changes on the same page.
Complex detection equipment can switch between different measurement pages through menus.
Devices with alarm functions can use icons, inverse video, or blinking to highlight abnormal states.

However, actual readability is also related to font size, contrast, viewing distance, and refresh method; the effect cannot be judged solely by resolution. Contrast is the degree of difference between bright and dark areas in an image; the more appropriate the contrast, the easier it is generally for field personnel to recognize characters and graphics.

The International Electrotechnical Commission (IEC) has specified requirements for liquid crystal display devices and related tests in the IEC 61747 series of standards; engineering selection should also refer to product datasheets and reliability test records.

If the equipment is installed in an environment with noticeable vibration, temperature differences, or dust, the temperature, damp heat, vibration, and other items should be checked in accordance with the GB/T 2423 series environmental test standards.
Relevant performance should be based on test reports, product specifications, or sample test results.
Source notes: IEC 61747 series standards, International Electrotechnical Commission (IEC), for reference on liquid crystal display devices and related test requirements; GB/T 2423 series standards, national standards, mainly for reference on environmental test items.

3. Four Criteria for Selecting Instruments and Meters

1. Consider Display Content and Software Complexity

If the interface mainly consists of numbers, units, and a few status words, a character LCD module is usually easier to implement. If Chinese prompts, icons, curves, or dynamic menus are needed, a graphic LCD module can provide more flexible interface design, but requires a supporting font library, driver, and display buffer.

Fixed numbers, English text, and status information: prioritize evaluating character LCD modules.
Chinese prompts, curves, icons, and dynamic menus: prioritize evaluating graphic LCD modules.
When dynamic refresh or multi-page switching is required, controller resources and software development workload should be evaluated in advance.

A font library is a collection of characters pre-stored in the system, used to quickly call up Chinese, English, numbers, or special symbols; if the target language or special symbols are numerous, confirm whether the module supports the required font library, or whether the controller can generate characters itself.

2. Consider Installation Space and Viewing Distance

In limited panel space, first check the viewing area, overall dimensions, and mounting holes, then compare character height and pixel resolution.

Check whether the viewing area can fully display the target content.
Check whether the overall dimensions, mounting holes, and cable routing direction match.
Confirm character height, contrast, and viewing angle based on the viewing distance between the operator and the equipment.
The final readability should not be judged solely by resolution or the number of displayable characters.

ISO 9241-11 emphasizes that the usability of a display system must be evaluated in the context of tasks, users, and the usage environment; therefore, the instrument screen should not only pursue information capacity, but also pay attention to whether field personnel can quickly read it.

Usability refers to the extent to which a user can effectively, accurately, and easily complete operations in a specific task, user group, and usage environment.
Source notes: ISO 9241-11, a standard related to human-computer interaction and usability, for reference in interface usability and usage environment evaluation.

3. Consider Controller Resources and Interface Conditions

Character LCD modules are usually suitable for control systems with limited resources, while graphic LCD modules may require more video memory, refresh control, and font resources. When selecting, confirm the parallel or serial interface, power supply range, initialization method, and whether the controller supports the target communication timing.

Confirm the type of parallel interface or serial interface.
Confirm the operating voltage, startup method, and initialization process.
Confirm whether the controller has sufficient display buffer and font library space.
Confirm whether the refresh rate meets the display requirements for curves, animations, or real-time data.

Initialization is the process in which, after the device is powered on, the controller sets the operating state of the LCD module according to a specified procedure; if the initialization timing does not match, problems such as no display, garbled characters, or unstable display may occur.

Specific electrical parameters must be subject to the documentation of the corresponding 金鹏 model; price, lifespan, and performance data are for reference only.

4. Consider Subsequent Maintenance and Mass Production

From a maintenance perspective, character LCD modules have regular interfaces, making replacement and troubleshooting relatively straightforward; graphic LCD modules facilitate future feature additions, but require stricter software version management.

Character modules are suitable for instruments with fixed interfaces and high batch consistency requirements.
Graphic modules are suitable for devices with continuously expanding functions that require multi-page or graphical displays.
Before mass production, confirm the consistency of screen display, interface connections, software versions, and mounting structure.
It is recommended to first build a prototype and at least verify display readability, environmental adaptability, and operation flow.

The National Institute of Standards and Technology (NIST) of the United States has emphasized in its usability engineering research that human-machine interfaces should be verified through real tasks, rather than relying solely on developers' subjective judgment.

Source notes: Research materials on usability engineering from the National Institute of Standards and Technology (NIST), for reference on human-machine interface task verification and usability evaluation.

4. 金鹏's Selection Recommendations for LCD Modules

For electric energy meters, temperature controllers, counters, and basic detection instruments, 金鹏 recommends starting with character LCD modules, with focus on confirming the number of characters, backlight color, viewing angle, operating temperature, and interface definition.

If the information mainly consists of numbers, units, and status words: prioritize evaluating character LCD modules.
If trend charts, complex menus, Chinese prompts, or multiple status icons are required: evaluate graphic LCD modules.
If installation space is limited: prioritize checking the overall dimensions, viewing area, mounting holes, and cable positions.
If the operating environment is complex: focus on operating temperature, damp heat, vibration, and reliability test records.
For mass production: it is recommended to complete sample testing and software interface verification before finalizing the design.

If the equipment needs to display trend charts, complex menus, Chinese prompts, or multiple status icons, graphic LCD modules can be evaluated, and the font library and software interface should be planned in advance.

In summary:

For instruments with fixed information, high cost sensitivity, and short development cycles, prioritize character LCD modules.
For instruments with continuously expanding functions and interfaces that need graphical presentation, prioritize graphic LCD modules.
When installation space, interface method, or operating environment has limitations, make the final decision based on sample testing.

金鹏 can assist in completing specification matching based on display content, structural dimensions, and control system conditions. The final model should be subject to sample testing, product specifications, and relevant standard requirements.