Beckhoff EL5042 EtherCAT Encoder Terminal

The Beckhoff EL5042 is an EtherCAT terminal with a two-channel encoder interface supporting BiSS-C (unidirectional) and SSI (Synchronous Serial Interface) protocols. This module enables direct connection of absolute encoders with BiSS-C or SSI interfaces, including both singleturn and multiturn encoders, to an EtherCAT network. The EL5042 acts as a BiSS-C master, transmitting clock signals to the encoder and receiving data over a serial interface. It is ideal for high-precision position feedback in motion control, robotics, and positioning applications.

Technical Specifications

The EL5042 features two independent encoder channels. Encoder operating voltage: external 5 V (supplied via optional ZK1090 cable) or 9 V (generated from the power contacts). The total current for both encoders is 0.5 A. The terminal supports unidirectional BiSS-C protocol (data transmission triggered by master clock) and SSI protocol (compatible with standard SSI encoders). Data transmission is clocked by the EtherCAT master. The terminal is designed to work with encoders from various manufacturers. Key specifications include: E-bus current consumption typical: 250 mA (depending on encoder load). The module is compliant with the CANopen over EtherCAT (CoE) protocol. The EL5042 is designed for use with Beckhoff EK1100 or EK1501 EtherCAT couplers. Operating temperature range: 0°C to 55°C. Storage temperature: -25°C to 85°C. Protection rating: IP20. Dimensions: 12 mm (W) × 100 mm (H) × 68 mm (D). The terminal mounts on a 35 mm DIN rail.

Key Features

• 2 encoder channels (BiSS-C unidirectional, SSI)

• Supports singleturn and multiturn absolute encoders

• BiSS-C master function (unidirectional)

• SSI (Synchronous Serial Interface) support

• Selectable encoder supply voltage: 5 V (external) or 9 V (internal)

• Total encoder supply current: 0.5 A

• Clock transmission triggered by master clock

• Timeout detection for end of data transmission

• Compatible with Beckhoff ZK1090 series cable sets for encoder connection

• Integrated status LEDs for each channel

• Configuration via CoE (CANopen over EtherCAT)

BiSS-C and SSI Protocol Support

The EL5042 supports the unidirectional BiSS-C protocol, which is a high-speed serial interface commonly used with absolute encoders for motion control. Data transmission is triggered by the master clock (generated by the EL5042). The end of data transmission is identified with a timeout. This protocol allows the reading of singleturn position (position within one revolution), multiturn position (number of revolutions), and encoder status/error bits. The module also supports the widely used SSI protocol, enabling connection of legacy SSI encoders. The EL5042 can be configured via CoE objects to match the encoder's data format (number of data bits, code type, baud rate). Supported baud rates are determined by the encoder requirements and the EtherCAT cycle time.

EtherCAT Integration

The EL5042 communicates with the Beckhoff EtherCAT system via the E-bus interface. It supports distributed clocks for precise synchronization of position data with the EtherCAT cycle. Configuration is performed in TwinCAT engineering environment, which automatically detects the terminal and assigns process data objects. The user selects the encoder type (SSI or BiSS-C) and configures the data format (e.g., 25-bit singleturn + 12-bit multiturn). The EL5042 then reads the position value and presents it as a 32-bit integer value in the process image. Diagnostic information (encoder error, data validity) is also available. The module supports both position and velocity data from encoders that provide velocity information.

Applications

The EL5042 is used in applications requiring precise absolute position feedback, including machine tools (spindle and feed axes), robotic systems (joint angle feedback), linear and rotary positioning stages, packaging machinery (cut-to-length registration), and printing presses (paper tension control). The SSI support allows connection of cost-effective SSI encoders, while BiSS-C support provides high-speed, high-resolution feedback for advanced motion control applications. The two-channel configuration allows a single terminal to serve two axes, reducing hardware cost and panel space.

Installation and Wiring

Install the EL5042 in an EtherCAT terminal strand by attaching it to the right side of an EtherCAT coupler (e.g., EK1100) or to an existing terminal. Use the double slot and key connection system for side-by-side mounting. Connect the BiSS-C or SSI encoder to the terminals using Beckhoff ZK1090 series cables (ZK1090-9191-xxxx or similar) or custom wiring. Pinout for the encoder connection: Data+, Data-, Clock+, Clock- (for BiSS-C and differential SSI). For single-ended SSI signals, appropriate wiring adaptations may be required. The EL5042 provides encoder power on the terminals (5 V or 9 V). The terminal automatically detects the presence of encoders and signals any wiring errors via the status LEDs. The module must be installed in a control cabinet with adequate clearance for heat dissipation.

Configuration and Diagnostics

Configuration of the EL5042 is performed via CoE (CANopen over EtherCAT) objects in TwinCAT. Key parameters include: encoder protocol (BiSS-C or SSI), data length (bits), position format (Gray code or binary), baud rate, sampling rate, and encoder supply voltage selection. The module provides diagnostic information including wire break detection, invalid data detection, and encoder communication errors. Status LEDs: green (run) for power and E-bus communication, and per-channel LEDs for encoder activity and errors. The TwinCAT System Manager displays real-time position data and diagnostic information for each channel.

Product Comparison

Beckhoff offers several encoder interface terminals. The EL5042 supports BiSS-C (unidirectional) and SSI, whereas EL5001 and EL5002 support SSI only. The EL5001 has one channel, while the EL5002 has two channels (SSI only). The EL5042 is the only 2-channel terminal that supports BiSS-C unidirectional. For BiSS-C bidirectional communication (with data feedback), other terminals are required. The encoder operating voltage for the EL5042 is 5 V or 9 V, whereas some other terminals provide 24 V encoder supply directly from the power contacts.

Environmental and Compliance

The EL5042 is CE and UL certified. It is RoHS compliant. Operating temperature: 0°C to 55°C. Storage temperature: -25°C to 85°C. Humidity: 5-95% non-condensing. Vibration resistance: 2g (10-55 Hz). Protection rating: IP20. The terminal must be installed in a control cabinet.

Conclusion

The Beckhoff EL5042 EtherCAT terminal provides a compact, high-performance interface for BiSS-C and SSI absolute encoders. Its two independent channels, flexible configuration, and direct integration into the EtherCAT system make it an excellent choice for precision position feedback in motion control applications.