EL3021 by Beckhoff

The EL3021 analog input terminal is produced by Beckhoff and belongs to the EL EtherCAT Terminals series. This compact module occupies a single slot on an EtherCAT I/O strand and converts voltage signals from field devices into a format the controller can process. By capturing a differential measurement on one channel, it allows PLCs and IPCs to supervise pressure transmitters, position encoders, or other analog sensors without long analog cable runs, supporting precise, distributed data acquisition in industrial automation environments.

The terminal accepts one differential input referenced to ground, and reliable operation is maintained when the sensor's common-mode voltage stays within 10 V. Internal circuitry resolves each sample to 12 bits, giving a 0.024% step size over the full span. Conversion is paced by the hardware, with a new value available every 0.625 ms. An analog filter with a 1 kHz cutoff attenuates unwanted high-frequency energy before digitization. Acquisition occurs simultaneously with any other channels present in the EtherCAT node. The total measuring deviation does not exceed ±0.3% of full scale, so most standard field signals can be recorded without calibration.

The EL3021 typically draws 130 mA from the EtherCAT E-bus, a value to consider when assembling high-density terminal strings. Its input path presents 85 ? plus the forward voltage of a protection diode, which limits inrush current while maintaining accuracy. Up to 40 mA can be sourced at the input terminal for sensor excitation, and the adjacent shield contact supports 100 mA to conduct interference currents to ground. Digital data arrive in the controller as a process image that dedicates 2 bytes to status bits and 2 bytes to the measured value, simplifying mapping in the PLC task. The housing carries an IP20 rating, which provides protection against finger contact but does not protect against water. Installation must therefore occur inside a suitable control cabinet or enclosure.