EtherCAT (Ethernet for Control Automation Technology) is a high-speed, real-time industrial network protocol designed for automation and data acquisition systems. Beckhoff Automation originally developed it and is now standardized under IEC 61158. Unlike regular Ethernet communication, EtherCAT is built for determinism and low latency: an EtherCAT master sends out a frame that each slave device (sensor, actuator, I/O module, etc.) processes on the fly. As the frame passes through, slaves write their data to and read data from it, then the frame returns to the master – all in one continuous stream. This makes EtherCAT extremely fast and efficient for connecting dozens of devices with minimal delay. In practical terms, a data acquisition system using EtherCAT can gather synchronized measurements from many modules (voltage, thermocouple, strain, etc.) with cycle times in the order of 100 μs to a few milliseconds, which is much faster than traditional fieldbuses.

An EtherCAT network is typically a daisy-chained or ring topology (it can be line, star, or tree as well). Each EtherCAT slave is assigned an address, but the EtherCAT frame is not stopped and started at each device – it’s processed as a continuous telegram that hardware in the slave devices handles in real-time. This protocol brings the “power and flexibility of Ethernet” to industrial control, but ensures the timing determinism needed for control loops and synchronized acquisition. For example, you might have an EtherCAT master in a PC or PLC, and multiple EtherCAT-capable measurement modules daisy-chained. The master sends a request frame, and within a few microseconds, each module has inserted its current sensor readings into the frame and passed it along. When the frame comes back, the master has all measurements virtually simultaneously. In summary, EtherCAT is a real-time Ethernet fieldbus for industrial automation, known for its high speed, low jitter, and ability to connect a large number of I/O devices easily.