EL3124 by Beckhoff

The EL3124 is an analog input terminal produced by Beckhoff for its EL EtherCAT Terminals series. It digitizes low-level sensor voltages and forwards the sampled words to the EtherCAT process image, allowing a PLC to supervise four separate measurement channels through the E-bus backplane. The module fits into the compact slice format commonly used in decentralized control cabinets and supports deterministic data exchange inside time-sensitive automation cells.

This terminal provides 4 differential input channels, each converted with a resolution of 16 bits. A built-in analog front end applies a 5 kHz filter so that higher-frequency noise is attenuated before sampling. The common-mode range extends to 10 V; within that window, the converter maintains linearity without clipping relative to the internal ground reference. Protection circuitry tolerates wiring errors up to 30 V on any pin, safeguarding the bus coupler and upstream sensors during installation. The terminal updates the EtherCAT process image with four 16-bit measurement words while reporting channel diagnostics through four 8-bit status bytes. It can also synchronize conversions to Distributed Clocks for network-wide time alignment.

The input electronics draw up to 40 mA from the E-bus supply, which simplifies power distribution because no external terminal voltage is required. An IP20 housing protects the circuitry from accidental finger contact but is suitable only for clean cabinet interiors. The terminal uses multiplex sampling to connect each channel sequentially to the converter, keeping the component count low while meeting typical control-loop bandwidth requirements. Its differential inputs reduce the effects of ground loops when sensors are installed far from the control panel. This input arrangement also improves rejection of electrical interference shared by both conductors. Status data allows the controller to identify channel conditions separately from the measured process values.