Product Description:

The EL3312 thermocouple input terminal is produced by Beckhoff within the EL EtherCAT Terminals series. Designed for DIN-rail automation, the module digitizes temperature signals from field sensors and places the measured values directly on the EtherCAT I/O bus for CPU processing. In common process lines, it provides localized temperature acquisition so that controllers receive real-time data without requiring separate analog input cards.

The EL3312 handles type K, type J, and other standard thermocouples through its two channels, each of which uses a two-wire connection technique that simplifies terminal strip layout. A dedicated cold-junction sensor helps maintain accuracy; the overall conversion error remains within ±2.0 °C, and thermal drift is limited by a cold-junction temperature coefficient of 40 mK/K. The module digitizes sensor voltage with a 16-bit converter, providing a display resolution of 0.1 °C before the controller scales the measurement. Electrical separation from the EtherCAT network is provided by 500 V of bus isolation, helping prevent ground loops between field probes and control electronics. The A/D stage draws power from the E-bus and has a rated consumption of 200 mA, which must be considered when assembling terminal strings.

The input stage includes an analog filter with a cutoff frequency of 1 kHz, allowing it to reject high-frequency noise while preserving transient temperature changes. Cable runs between the sensors and terminal can extend to 30 m without affecting resolution when shielded wire pairs are used. The module installs on a 35 mm mounting rail, and its open-circuit detection reports broken thermocouple leads through the controller diagnostics. During operation, the terminal contributes 16 bytes to the process-image input and 8 bytes to the output area, supporting parameter transfers such as offset adjustments. The enclosure provides IP20 protection, and each measured value is supplied to the PLC at a resolution of 0.1 °C per digit.