Overview
What are Text Displays?
Industrial text displays are character-based Operator Interface Terminals (OIT) used to monitor machine status, view diagnostic codes, and adjust process parameters. Unlike complex graphic touchscreens, these devices focus on high-readability alphanumeric data. They typically utilize LCD, LED, or Vacuum Fluorescent Display (VFD) technology and are paired with physical function keys or numeric keypads. Because they lack the overhead of high-resolution operating systems, text displays offer near-instant boot times and exceptional longevity in electrically noisy environments.
Main Manufacturers
While many manufacturers have transitioned to full-color graphic HMIs, several industry leaders continue to provide and support robust text-based interfaces for specialized and legacy applications:
- Siemens: Known for the SIMATIC OP (Operator Panel) and TD (Text Display) series.
- Allen-Bradley / Rockwell Automation: Featuring the PanelView Component and legacy PanelView 300/550 lines.
- Schneider Electric / Magelis: Providing compact XBTN and XBTR small panels.
- Mitsubishi Electric: Supporting the GOT1000 and legacy FX series text displays.
- Red Lion: A leader in protocol-converting text displays and large LED plant floor displays.
Typical Applications
Text displays are favored in applications where "at-a-glance" data is required without the need for complex visualization. Common use cases include:
- Pump Control & Water Treatment: Displaying flow rates, tank levels, and pressure setpoints.
- Conveyor Systems: Monitoring motor speeds and fault codes (e.g., E-Stop or Jam detected).
- HVAC Systems: Setpoint adjustment and sensor feedback in commercial buildings.
- Material Handling: Simple operator instructions for picking or sorting tasks.
- OEM Machinery: Providing a cost-effective diagnostic port for field service technicians.
Selection Guide
When sourcing a replacement or specifying a new text display, prioritize the following technical specifications:
- Character Matrix: Define the required lines and characters (e.g., 2 lines x 20 characters vs. 4 lines x 40 characters).
- Input Type: Choose between function keys (F1-F8), numeric keypads for setpoint entry, or simple read-only displays.
- Connectivity: Ensure the hardware supports your PLC’s port (RS-232/485) and protocol (Modbus, Profibus, or proprietary links like Allen-Bradley DH-485).
- Environmental Rating: Confirm the unit meets IP65 or NEMA 4X standards if it will be exposed to liquids or fine dust.
- Backlighting: For low-light environments, LED-backlit LCDs offer the longest service life compared to older CCFL technology.
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Frequently asked questions
What is the difference between an HMI text display and a graphic panel?
A text display is an HMI designed primarily for alphanumeric status messages and data entry via a tactile keypad. Unlike graphic touchscreens, text displays use character-based LCD or VFD screens (e.g., 2x16 or 4x20 characters) and offer higher durability in high-vibration or extreme temperature environments.
What communication protocols do text displays typically use?
Most industrial text displays support RS-232, RS-422, or RS-485 serial communication using protocols like Modbus RTU, DF1, or PPI. Modern units may also feature Ethernet ports for Modbus TCP or EtherNet/IP connectivity.
How do I select a replacement for an obsolete text display?
Check the cut-out dimensions, supply voltage (typically 24V DC), and communication protocol compatibility. If the original software is unavailable, you may need a universal display (like those from Red Lion or Beijer) that supports the existing PLC driver.
Can text displays be used in harsh washdown environments?
Yes, industrial text displays are often rated NEMA 4/4X or IP65/66 on the front face, making them resistant to dust, moisture, and washdown procedures, which is why they are preferred in food processing and outdoor applications.
How are messages programmed into a text display?
Text displays are programmed using manufacturer-specific software, such as Allen-Bradley PanelBuilder1200/32, Siemens STEP 7 (for integrated displays), or dedicated configuration tools for third-party serial displays. Many allow for 'canned messages' triggered by PLC register values.