Beckhoff EL1904 TwinSAFE Digital Input Terminal
A four-channel 24 V DC fail-safe input terminal for potential-free safety sensors in an EtherCAT I/O station.
Technical Summary
EL1904 is a Beckhoff TwinSAFE input terminal that transfers safety sensor states to a TwinSAFE Logic-capable component through Safety over EtherCAT. It accepts potential-free contacts and supports channel-specific safety evaluation.
The safety parameters are supplied by the TwinSAFE logic when the application starts. Replacement therefore depends on a validated safety project, correct wiring and a completed commissioning test rather than on terminal exchange alone.
Specifications
| Manufacturer | Beckhoff |
|---|---|
| Model | EL1904 |
| Connection Technology | 1-/2-wire |
| Fail-Safe Inputs | 4 |
| Input Supply | 24 V DC |
| Protocol | TwinSAFE / Safety over EtherCAT |
| Typical Response Time | 4 ms |
| E-bus Current Consumption | Typically 200 mA |
| Safety Capability | Cat. 4 / PL e and SIL 3 |
| Installation Position | Horizontal |
| Protection Rating | IP20 |
| Mounting | 35 mm DIN rail |
Features
- Cross-circuit detection supports supervised safety-input wiring.
- One-channel or two-channel evaluation can be selected within the validated safety configuration.
- Individual channel testing can be enabled to suit the connected sensors.
- Transferred safety parameters simplify like-for-like service replacement after the project is restarted.
Compatibility
- Use with a Beckhoff EtherCAT station and TwinSAFE Logic-capable component.
- Connect only sensors and circuits covered by the validated machine safety design.
- Supply the terminal from a compliant 24 V DC SELV/PELV source and preserve the intended power-contact arrangement.
Replacement
- Save and verify the TwinSAFE project before disturbing the terminal.
- Record terminal position, wiring, serial number and safety-device channels.
- After exchange, reload the safety parameters and complete the required commissioning validation before release.
FAQ
Can EL1904 be replaced without changing the TwinSAFE project?
A like-for-like hardware exchange can receive its parameters from the TwinSAFE logic, but the safety project and terminal assignment must still be verified and the machine safety function retested.
What sensors are appropriate for EL1904?
Use potential-free safety contacts and connection methods covered by the validated safety circuit, including the required one- or two-channel evaluation.
How should EL1904 cross-circuit detection affect field wiring?
Route and configure the channels so the configured test pulses and diagnostic behavior remain valid for the sensor and cable architecture.
What information is needed when quoting EL1904 for an existing machine?
Provide the terminal position, TwinSAFE project version, sensor type, wiring diagram, current terminal revision and any diagnostic message.
Can a standard digital input terminal replace EL1904?
No. A standard terminal does not provide the certified TwinSAFE input path or the validated safety behavior required by the application.
What must be documented after EL1904 replacement?
Record the new serial number, project checksum, parameter transfer, wiring inspection and completed safety-function validation.
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