EL3122 by Beckhoff

The EL3122 is a two-channel analog input module produced by Beckhoff as part of the EL EtherCAT Terminals series. Designed for DIN-rail installation inside decentralized control cabinets, the terminal digitizes process currents from field transmitters and forwards the data to an EtherCAT controller in real time. By converting 4-20 mA signals into 16-bit values, it facilitates precise monitoring of pressure, flow, and level loops in industrial automation.

Each channel is electrically isolated, and the terminal offers a total of 2 differential inputs referenced to a common ground path. The 16-bit sigma-delta converter provides a digital resolution of 16 bits, allowing the PLC to detect small changes in loop current. The accepted signal amplitude covers the industry-standard range of 4-20 mA, while an internal resistance of 85 ? develops the corresponding voltage drop inside the device. Absolute linearity is maintained within <±0.3% FS, limiting scaling errors during calibration. Transient disturbances are attenuated by an input filter set to 5 kHz, while the simultaneous sampling architecture and Distributed Clocks feature keep both channels aligned with sub-microsecond timing. At the field wiring point, the module can conduct up to 40 mA without overloading the contacts.

The input stage tolerates a common-mode offset of up to 10 V maximum, enabling reliable operation near high-power drives. The operating temperature range extends from -25 to +60 °C, and the housing can withstand storage temperatures as low as -40 °C. Protection against accidental contact is provided by the IP20 enclosure, and the 12 mm-wide body mounts on a 35 mm DIN rail according to EN 60715. Internal electronics draw a typical current of 170 mA from the E-bus, allowing several terminals to be daisy-chained without exceeding the EtherCAT coupler's power budget. Process data are transferred to the controller image as a 2 × 16-bit value accompanied by channel status information.