EL3174 by Beckhoff

The EL3174 is a four-channel analog input terminal manufactured by Beckhoff for the EL EtherCAT Terminals series. It converts differential or single-ended field measurements into digital data that travels through the EtherCAT backplane, allowing PLCs to capture process parameters with millisecond precision. Because it participates in the EtherCAT Distributed Clocks mechanism, the terminal aligns every conversion with the network reference time. This synchronization supports coordinated motion and data logging applications in machine tools, packaging lines, and process skids.

An internal successive-approximation register converter samples each channel through time-division multiplexing. The module accepts four analog inputs, and every sample is inserted into the network with an EtherCAT cycle time of 200 µs. Before conversion, a hardware filter limits the input bandwidth to 5 kHz, removing higher-frequency noise that could cause aliasing in the measurement. The conversion depth is 16 bits, so the full-scale range is quantized into 65,536 discrete levels. Common-mode voltage may reach 35 V without affecting accuracy. The ground reference is differential for voltage channels, while current channels share a single-ended return. Distributed Clocks support provides sub-microsecond alignment between this terminal and motion axes driven from the same bus.

The digitized values occupy a process image of 16 bytes, which the controller reads in one deterministic transaction. Field installation follows Beckhoff passive-ventilation guidelines because the housing is rated IP20. The terminal electronics draw up to 40 mA from the auxiliary 5 V rail, and this current must be included when sizing the power feed. The input circuitry includes protection against reverse polarity and short-term overdrive. Voltage channels have an absolute maximum input of 50 V, while current channels have an absolute maximum of 30 V without physical damage.