R. STAHL 200020670200 ET-125-RS422 Open HMI Panel
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Product Information
The R. STAHL ET-125-RS422 (part number 200020670200) is a 10.4-inch human-machine interface panel from the Open HMI Series 100 engineered for process control and visualization in hazardous locations. Designed for direct installation in Zone 1, 2, 21, and 22 classified atmospheres, this operator interface panel provides graphical visualization, system monitoring, and alarm displays without requiring cumbersome explosion-proof housings. The terminal incorporates a bright VGA TFT display delivering 640 x 480 pixel resolution, backed by an IP65-rated front panel that protects the device from dust ingress and industrial washdown. Operating on a nominal 24 V DC supply voltage across an allowable range of 18 to 32 V DC with a rated current of 1.5 A, it is well suited for demanding processing environments.
For host connectivity and communication, the ET-125-RS422 features a primary RS-422 serial interface utilizing a standard 9-pin Sub-D connector, alongside a USB Type A service port for field maintenance. The serial port interfaces seamlessly with major programmable logic controllers, supporting Modbus RTU master/slave communications and direct drivers for Siemens S7, Rockwell Automation, and Schneider Electric automation platforms. Commissioning a replacement terminal requires loading the runtime screen project and parameter sets via non-volatile Flash memory or CompactFlash storage using SPS-Plus WIN engineering software. A replacement unit cannot operate without this project transfer and protocol configuration, and ABC Industrial Parts can assist technical teams with preparing spare units and restoring operational files.
System health and operational state are monitored through a combination of hardware LEDs and software diagnostic functions. Front-panel status indicators include a POWER / RUN indicator to verify power supply and runtime status, as well as a COM / TX / RX indicator to confirm active serial communications on the RS-422 line. Diagnostics can also be run using the boot self-test sequence, the on-screen setup menu, runtime error displays, or SPS-Plus WIN diagnostic mode. When the power LED remains unlit despite verifying the 18 to 32 V DC power source and wiring, an internal component fault is indicated that cannot be serviced in the field. In such instances, sourcing a tested replacement unit or arranging repair through ABC Industrial Parts offers the most efficient solution to restore machine visualization.
Technical Specifications
| Manufacturer | R. STAHL |
| Part Number | 200020670200 |
| Model / Type | ET-125-RS422 |
| Product Family | Open HMI Series 100 |
| Component Type | HMI Panel |
| Display Size | 10.4 inch |
| Display Resolution | 640 x 480 pixels |
| Display Type | VGA TFT |
| Hazardous Area Certification | Zone 1, 2, 21, 22 |
| Nominal Supply Voltage | 24 V DC |
| Supply Voltage Range | 18 - 32 V DC |
| Rated Current | 1.5 A |
| Ingress Protection Rating | IP65 (front) |
| Primary Serial Interface | RS-422 |
| Serial Port Connector | Sub-D 9-pin |
| Service Interface | USB Type A |
Programming and Configuration
Project development, screen design, and parameter management for the R. STAHL ET-125-RS422 are performed using SPS-Plus WIN engineering software. The software allows control engineers to build custom visualization projects, configure alarm messaging, and establish communication parameters tailored to the host controller.
To safeguard project integrity against unexpected power interruptions, the ET-125-RS422 relies on non-volatile Flash memory for permanent storage of screens, parameter sets, and system files. Additional storage support is available via CompactFlash memory cards, enabling quick project uploads, downloads, and backups during field maintenance or replacement tasks.
Communication and System Integration
The ET-125-RS422 provides a built-in RS-422 serial port accessed through a standard 9-pin Sub-D connector. This interface allows reliable high-speed serial communications across long distance runs typical of chemical, petrochemical, oil and gas, and pharmaceutical processing plants.
The operator terminal supports Modbus RTU in both master and slave roles, ensuring compatibility with standard industrial networks. It also features controller drivers to establish direct serial communications with major PLC systems, including Siemens S7, Rockwell Automation, and Schneider Electric platforms. A USB Type A service port is available on the panel to simplify local maintenance and file transfer operations.
Diagnostics and Status Indication
The R. STAHL ET-125-RS422 offers comprehensive diagnostic mechanisms to monitor unit health and serial communications. During startup, the terminal executes an automated boot self-test sequence. Operational statuses and fieldbus communications are further monitored via the on-screen system setup menu, runtime status codes displayed directly on visualization screens, and dedicated diagnostic tools in SPS-Plus WIN.
Status LED Indicators
| LED | Color/Status | Meaning |
|---|---|---|
| POWER / RUN | Indicates system operating voltage presence and runtime operation status; unlit indicates loss of power or internal hardware fault | |
| COM / TX / RX | Indicates active communication traffic over the RS-422 serial line |
Replacement and Spare Part Considerations
When replacing an existing R. STAHL ET-125-RS422 (part number 200020670200), verify that the target environment matches the unit's Zone 1, 2, 21, or 22 hazardous area classifications. Ensure that the incoming power line delivers a steady DC voltage within the permissible 18 to 32 V DC operating window (24 V DC nominal).
A replacement terminal will not operate on the machine out of the box without project initialization. Maintenance technicians must restore the project file and parameters using SPS-Plus WIN or an existing CompactFlash backup card. Confirm that the serial interface configuration, baud rates, and PLC driver settings on the replacement match the original HMI node to re-establish RS-422 communication without error.
Frequently Asked Questions
Which software is used to program the R. STAHL ET-125-RS422?
The terminal is configured and programmed using R. STAHL SPS-Plus WIN engineering software, which handles screen development, project uploads, downloads, and communication driver settings.
Can the ET-125-RS422 be installed directly in hazardous areas?
Yes, the ET-125-RS422 is certified for direct installation in Zone 1, 2, 21, and 22 hazardous environments without requiring an additional heavy explosion-proof housing.
What communication interfaces are built into the ET-125-RS422?
The terminal features a primary RS-422 serial interface using a Sub-D 9-pin connector for PLC communications, as well as a USB Type A service port for maintenance.
Which PLCs and protocols are supported by this panel?
The ET-125-RS422 supports Modbus RTU master/slave protocols as well as serial drivers for Siemens S7, Rockwell Automation, and Schneider Electric PLCs.
What should I check if the POWER / RUN LED remains unlit?
First check the external power supply and wiring to ensure the input voltage is within the 18 to 32 V DC range. If incoming power is verified but the LED stays unlit, an internal hardware failure is present and the panel requires repair or replacement.
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Data backup and recovery
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Specific firmware and hardware versions
If you are working with specific hardware or firmware versions that are no longer available from the manufacturer, ABC Industrial Parts is your partner. When making your enquiry, clearly state which versions you need, we will then look at the possibilities of supplying those versions, so that your installations continue to function optimally.
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