Product Description:

The EL3311 is a single-channel thermocouple input terminal produced by Beckhoff for the EL EtherCAT Terminals series. In temperature-controlled machinery, it converts microvolt-level sensor outputs into deterministic process data that a PLC can read over EtherCAT. By integrating cold-junction compensation and electrical isolation, the device reduces the need for ancillary hardware and simplifies thermal acquisition loops in industrial automation.

Bus-side isolation of 500 V decouples the sensor circuit from the network backplane and helps block ground loops. The terminal measures within an electrical span of ±75 mV, matching the output range of most mineral-insulated type K thermocouples. A sigma-delta converter provides a native resolution of 16 bits, while PDO scaling of 4 µV/digit enables the detection of small thermal gradients. Cold-junction compensation has an accuracy of ±2.0 °C, and an internal sensor performs this correction automatically for the channel. Differential voltage to ground is limited to ±2 V. Open-circuit detection activates diagnostic flags when the sensor wiring is interrupted, allowing the control system to distinguish a wiring fault from a valid temperature reading.

Installation uses a 2-wire connection, minimizing field wiring and supporting cable runs up to 30 m without degrading measurement precision. The digitized temperature value has a preset granularity of 0.1 °C/digit, simplifying downstream calculations and process monitoring. The terminal has an IP20 protection rating, so it must be installed inside a control cabinet with suitable protection from dust and moisture. A cold-junction temperature coefficient below 40 mK/K limits additional error during normal ambient temperature changes. The terminal automatically identifies the default type K sensor when powered on. Its single input channel allows an individual terminal to serve each critical measurement point while retaining EtherCAT timing and direct integration with the machine control network.