EL3172 by Beckhoff

The EL3172 is a two-channel analog input module manufactured by Beckhoff within the EL EtherCAT Terminals series. As an I/O terminal, it digitizes voltage or current signals and places the measured data into the EtherCAT process image, allowing PLCs to monitor sensors and transducers in distributed automation systems. Configuration data are retained in nonvolatile NoCoE storage, preserving the terminal settings after a power loss and simplifying system restarts.

Each of its 2 differential inputs feeds a successive-approximation register (SAR) converter that delivers 16 bit resolution. A hardware input filter with a cutoff frequency of 5 kHz suppresses higher-frequency noise before conversion. Sampling occurs simultaneously on both channels to preserve phase relationships, and the terminal aligns its timestamps with the EtherCAT network through distributed clocks. The internal E-bus typically draws 140 mA, so power budgeting within a terminal string must account for this current. Functional isolation between the field and logic domains is rated at 707 V for 7 s, helping protect the controller from transient field potentials. The differential inputs reduce the effects of common-mode offsets, while the 16-byte process image maps raw values, status bits, and timestamp data to the master.

High-speed control tasks are supported by a minimum EtherCAT cycle of 175 µs, which works with simultaneous sampling to capture fast signal changes across both channels. Field wiring can carry up to 40 mA per contact, accommodating typical sensor connections while limiting terminal heating. The IP20 protection rating restricts the unit to cabinets or other protected enclosures, while the connection system permits tool-free push-in wiring. Internal shielding helps minimize crosstalk and preserve signal accuracy when the terminal operates alongside other EL series modules. Distributed clock synchronization also allows acquired values to be correlated accurately with measurements from other synchronized terminals in the EtherCAT network.